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N  THE  CUSTODY  OF  ThE 

BOSTON     PUBLIC   LIBRARY. 


^ SHELF    N° 


ADAMS 

103.13 


PHILOSOPHICA   L 


TRANSACTIONS, 


OF     THE 


ROYAL     SOCIETY 

O    F 

O      N      D      O      N. 

V  O  L.    LXXV.  For  the  Year  1785, 
PARTI, 


Samre/e. 


LONDON, 

IIOLD   BY    LOCKYER   DAVIS,    AND   PETER    ELMSLY, 
PRINTERS  TO  THE  ROYAL  SOCIETY. 

MDCCLXXXV. 


C5ieA..fi^3a/il,i 


^    *DAII8ia.B 


?t.ia/ 


■?/' 


V 


[     iii     ] 


ADVERTISEMENT. 


TH  E  Committee  appointed  by  the  Royal  Society  to  dire^l  the  pub- 
lication of  the  Fhilofophical  'TraJifatlions,  take  this  opportunity  to 
acquaint  the  Public,  that  it  fully  appears,  as  well  from  the  council-books 
and  journals  of  the  Society,  as  from  repeated  declarations  which  have 
been  made  in  feveral  former  Tranfdclions,  that  the  printing  of  them  was 
always,  from  time  to  time,  the  fingle  aft  of  the  refpeftive  Secretaries,  till 
the  Forty-feveuth  Volume :  the  Society,  as  a  Body,  never  intereflingthem- 
ielves  any  further  in  their  publication,  than  by  occafionally  recommending 
the  revival  of  them  to  fome  of  their  Secretaries,  when,  from  the  particular 
circumflances  of  their  affairs,  the  Tranfadions  had  happened  for  any 
length  of  time  to  be  intermitted.  And  this  feems  principally  to  have 
been  done  with  a  view  to  fatisfy  the  Public,  that  their  ufual  meetings 
were  then  continued  foj-  the  improvement  of  knowledge,  and  benefit  of: 
mankind,  the  great  ends  of  their  firfl:  inflitution  by  the  Royal  Charters, 
and  which  they  have  ever  fince  fteadily  purfued. 

But  the  Society  being  of  late  years  greatly  inlarged,  and  their  com- 
munications more  numerous,  it  was  thought  advifable,  that  a  Committee 
of  their  members  fliould  be  appointed  to  reconfider  the  papers  read  be- 
fore them,  and  feleft  out  of  them  fuch,  as  they  fhould  judge  moft  pro- 
per for  publication  in  the  future  'Tranfadions  ;  which  was  accordingly 
done  upon  the  26th  of  March  1752.  And  the  grounds  of  their  choice 
are,  and  will  continue  to  be,  the  importance  and  fingularity  of  the  fub- 
3  efts,  or  the  advantageous  manner  of  treating  them;  without  pretending 
to  anfwer  for  the  certainty  of  the  fafts,  or  propriety  of  the  reafonings, 
contained  in  the  fevtral  papers  f©  publiflied,  which  muft  dill  reii  on  the 
credit  or  judgment  <:f  their  refpeftive  authors* 

A  2  It 


E     iv     1 

It  ]s  likewife  neceiTary  on  this  occafion  to  remark,  that  it  is  an  efla--- 
bliflied  rule  of  the  Society,  to  which  they  will  always  adhere,  never  to 
give  their  opinion,  as  a  Body,  upon  any  rubje6t,  either  of  Nature  or  Art,. 
that  comes  before  them.     And  therefore  the  thanks,  which  are  fre- 
quently propofed  f\-om  the  chair,  to  be  given  to  the  authors  of  fuch  pa- 
pers as  are  read  at  their  accuftomed  meetings,  or  to  the  perfons  through: 
whofe  hands  they  receive  them,  are  to  be  confidered  in  no  other  light 
than  as  a  matter  of  civility,  in  return  for  the  refpefi  iliewn  to  the  Society 
by  thofe  communications.     The  like  alfo  is  to  be  faid  with  regard  to 
the  fever al  projects,  inventions,   and  curiofities  of  various  kinds,  which 
are  often  exhibited  to  the  Society  ;  the  authors  whereof,  or  thofe  wh^ 
exhibit  thera,  frequently  take  the  liberty  to  report,  and  even  to  certify 
in  the  public  news-papers,  that  they  have  met  with  the  highefl  applanfe 
and  approbation.     And  therefore  it  is  hoped,  that  no  regard  will  here-- 
after  be  paid  to  fuch  reports,  and  public  notices  ;  which  in  fome  inftances? 
have  beert  too  lightly  credited,  to  the  diflionour  of  the  Society, 


fj^'^^i.. 


■'"■■"*  ■■•  ■  '■"      ' -.—-,.-  . ,.   ...  -       ■ »- — ^  ^ 


CONTENTS 


O  F 


O  L.     LXXV.    Part    I. 


I*     ^'^  Account  of  an  arttficial  Spring  of  Water.     By  Eraf- 

mus  Darwin,  M.  T>.  F.  R,  S,  page  i 

-IL  An  Account  of  an  Englifli  Bird  of  the   Genus   Motacilla, 

fuppofed  to  be   hitherto    unnoticed  by  Britiih   Ornlthologljis  ; 

obferved  by  the  Rev.  John  Lightfoot,  M.  A.  F.  R.  S.    In  a 

Letter  to  Sir  Jofeph  Banks,  Bart,  P.  R.  S.  p.  8 

III,  An  Account  of  Morne  Garou,  a  Mountain  In  the  JJland  of 
St.  Vincent,  with  a  Defcrlptlon  of  the  Volcano  on  Its  Summit. 
In  a  Letter  from  Mr.  James  Anderfon,  Surgeon^  to  Mr. 
Forfyth,  His  Majefiys  Gardener  at  Kenlington ;  commtml" 
cated  by  the  Right  Honourable  Sir  George  Yonge,  Bart. 
F.R.S.  p.  i6 

IV.  A  Supplement  to  the  Third  Fart  of  the  Paper  on  the  Sum- 
mation of  Infinite  Series,  In  the  Philofophical    Tranfa6llons 

for 


vi  CONTENTS. 

for  the  Tear  1782.  By  the  Rev,  S.  Vlnce,  M.  A; 
commu?ilcated  by  Nevil  Mail'Celyne,  D,  D,  F,  R,  S,  a?id 
Aflronomer  Royal,  P*  32 

V.  Defer iption  of  a    Plant  yielding  Afa   fcetida.     In  a  Letter 

from  John   Hope,  M.  D.  F.   R.  S.  to  Sir  Jofeph  Banks, 

Bart,  P.  R  S,  p.  36 

V!.  Gifahgue  of  Double  Stars,  By  William  Herfchel,  Efq, 
F.  R.  S.  p.  40 

VII.  Obfervations  of  a  new  Variable  Star,  In  a  Letter  from 
Edward  Pigott,  Efq,  to  Sir  H.  C.  Englefield,  Bart.F.  R,  S, 
a?]d  A.  S.  P«  127 

Vill.     Afironomical  Obfervations^       In    two   Letters  from    M. 
Francis  de  Zach,  Profeffor   of  Mathematics^  and  Member   of 
the   Royal  Academies   of  Sciences  at  Marfeilles,   Dijon,   and 
Lyons,  to  Mr.  Tiberius  Cavallo,  F.  R.  S.  p.  137 

IX.  Obfervations  of  a  new  Variable  Star.  By  John  Goodrlcke, 
Efq. ;  communicated  by  Sir  H.  C.  Englefield,  Bart.  F.  R.  S, 
and  A.  S.  p.  I  ^"^ 

X.  On  the  Motion  of  Bodies  affeSicd  by  FriSlion,  By  the  Rev, 
Samuel  Vince,  A.M.  communicated  by  Ainhony  Shepherd, 
D.  D.  F.  R.  S,  Plumian  Profejfor  of  Afrommy  and  experi' 
77icntal  Philofophy  at  Q^rcihn^gQ.  P*  ^^5 

XL  Obfervations  and  Experiments  on  the  Light  of  Bodies  in  a 
State  of  Combuftion.  By  the  Rev.  Mr.  Morgan  ;  communicated 
by  the  Rev.  Richard  Price,  LL.D.  F.R.S.  p.  190 

XII.  On  theConjlrudiion  of  the  Heavens,  P^'WIUIam  Herfchel, 
Efq.  F.R.S.  p.  213 

XIII.  Remarks  on  fpecifc  Gravities  taken  at  different  Degrees  of 
Heat^  and  an  eafy  Method  of  reducing  them  to  a  common  Stan- 
J/ird.     By  Richard  Kirwan,  Efq.  F.R.S.  p.  267 

XI V, 


.0 


CONTENTS.  vu 

XIV.  Ele5frical  Experiments  made  in  order  to  ajcertain  the  non- 
condubling  Power  of  a  perjedl  Vacuum^  &c.  By  Mr.  Wil- 
liam Morgan  ;  communicated  by  the  Rev.  Richard  Price, 
LL.D.  F.R,S,  p.  272 

XV.  Experiments  and  Ohfervations  relating  to  Air  and  Water ^ 
By  the  Rev.  Jofeph  Prieftley,  LL.D.  F.R,S.  p.  279, 


THE  Prefident  and  Council  of  the  Royal  Society  adjudged, 
for  the  Year  1784,  the  Medal  on  Sir  Godfrey  Copley's 

Donation,  to  Edward  Waring,  M.  D.  Lucafian  Profeflbr 
pf  the  Mathematics  at  Cambridge,  for  his  Mathematical 
Communications  to  the  Society* 


PHILOSOPHICAL 


TRANSACTIONS. 


I.  An  Account  of  an  artificial  Spring  of  IFatev,     By  Erafmus 

Darwin,  M,  D,  F.  R,  S, 


Read  November  4,   1784. 
To  the  Prefident  and  Fellows  of  the  Royal  Society. 

GENTLEMEN,  Derby,  July  16,   1 784. 

CONFIDENT  that  every  atom  which  may  contribute  to 
increale  the  treafury  of  iifeful  knowledge,  whicli  you  are 
fo  fuccefsfully  endeavouring  to  accumulate,  will  be  agreeable 
and  intei^fting  to  the  Society,  I  fend  you  an  account  of  an 
artificial  fpring  of  water,  which.  I  produced  laft  fummer  near 
the  fide  of  the  river  Darwent  in  Derby. 

VoL.LXXV.  B  Near 


2       .  Z)r.  DAU'WiirSi'/^ccoufn  of 

Near  thy  houfe  was  an  old  well,  about  one  hundred  yards 
from  the  river,  and  about  four  yards  deep,  which  had  been 
many  years  difufed  on  account  of  the  badnefs  of  the  water, 
w^hich  I  found  to  contain  much  vitriolic  acid,  with,  at  the 
fame  time,  a  flight  fulphureous  fmell  and  tafte  ;  but  did  not 
Carefully  analyfe  it.  The  m.outh  of  this  well  was  about  four 
feet  above  the  furface  of  the  river  ;  an<l  the  ground,  through 
which  it  was  funk,  confifted  of  a  black,  loofe,  moiit  earth, 
which  appeared  to  have  been  very  lately  a  morafs,  and  is  now 
Covered  with  houfes  built  upon  piles.  At  the  bottom  was 
found  a  bed  of  red  marl,  and  the  fpring,  which  was  fo  ftrong 
as  to  give  up  many  hogfheads  in  a  day,  oozed  from  between 
the  morafs  and  the  marl :  it  lay  about  eight  feet  beneath  the 
iurf  ice  of  the  river,  and  the  water  rofe  within  two  feet  of  the 
top  of  the  well. 

Having  obferved  that  a  very  copious  fpring,  called  Saint 
Alkmund's  well,  rofe  out  of  the  ground  about  half  a  mile 
higher  on  the  fime  fide  of  the  Darwent,  the  level  of  which  I 
knew  by  the  height  of  the  intervening  wier  to  be  about  four  or 
five  feet  above  the  ground  about  my  w^ell ;  and  having  obferved, 
that  the  higher  lands,  at  the  diftance  of  a  mile  or  two  behind 
thefe  wells,  conlified  of  red  marl  like  that  in  the  well ;  I 
concluded,  that,  if  I  fhould  bore  through  this  ftratum  of  marl, 
i  might  probably  gain  a  water  fimilar  to  that  of  St.  Alkmund's 
well,  and  hoped  that  at  the  fame  time  it  might  rife  above  the 
furface  of  my  old  well  to  the  level  of  St.  Alkmund's. 

With  this  intent  a  pump  was  firft  put  down  for  the 
purpofe  of  more  eafily  keeping  dry  the  bottom  of  the  old  well, 
and  a  hole  about  two  and  an  half  inches  diameter  was  then 
bored  about  thirteen  yards  below  the  bottom  of  the  well, 
till  fome  l^-^nd  w^as  brought  by  the  auger.  A  wooden  pipe, 
^  which 


an  artificial  Spri^ig  of  lValct\  j 

wliicli  was  previoufly  cut  iu  a  conical  form  at  one  end,  an 4 
armed  with  an  iron  ring  at  the  other,  was  driven  into  the  top  of 
this  hole,  and  flood  np  about  two  yards  from  the  bottom  of 
the  well,  and  being  furrounded  with  well-rammed  clny,  the 
new  water  afcended  iu  a  fmall  ftream  through  the  wooden 
pipe. 

.Our  next  operation  was  to  build  a  wail  of  clay  againil:  the 
moraiiy  fides  of  t]ie  well,  with  a  wall  of  well-bricks  inter- 
nally, up  to  the  top  of  it.  This  completely  flopped  out  every 
drop  of  the  old  water;  and,  on  taking  out  the  plug  which 
had  been  put  in  the  wooden  pipe,  the  new  water  in  two  or 
three  days  role  up  to  the  top,  and  flowed  over  the  edges  of  the 
weJL 

Afterwards,  to  gratify  my  curiofity  in  feeing  how  high  the 
new  fpring  would  rife,  and  for  the  agreeable  purpofe  of  pro- 
curing the  water  at  all  times  quite  cold  and  frefh,  I  directed 
a  pipe  of  lead,  about  eight  yards  long,  and  three-quarters  of 
an  inch  diameter,  to  be  introduced  through  the  wooden  pipe 
defcribed  above,  into  the  flratum  of  marl  at  the  bottom  of  the 
well,  fo  as  to  fland  about  three  feet  above  the  lurface  of  the 
ground.  Near  the  bottom  of  this  leaden  pipe  was  fewed,. be- 
tween two  leaden  rins-S  or  {l^iieties,?  an  inverted  cone  of  iliff 
Ipatherjriiatp.jyhich  fome  wool  was, fluffed  to  ftretch  it  out,  fo 
that,  after  having  pafled  through  ttje  \yopden  pipe,  it  might 
'^completely  fill  .up  the  perforatipn  of  the  clay.  Another,  leaden 
ring  or  flanch  was  foldered  round  the  leaden  pipe,  about  two 
yards  below  th;e  fqrface  of  the  ground,  wdiich,  with  fome  dou- 
bles of  flannel  placed  under  it,  was  nailed  on  the  top  of  the 
-wooden  pipe,  by  w^hich  means  the  water  was  perfedlly  pre- 
cluded froni  rifing  between  the  wooden  and  the  leaden  pipes. 

B  2  Tliis 


4  Dr,  Darwin's  Account  of 

This  being  accompllfhed,  the  bottom  of  the  well  remained 
quite  dry,  and  the  new  water  quickly  role  about  a  foot  above 
the  top  of  the  wdll  in  the  leaden  pipe ;  and,  on  bending  the 
mouth  of  this  pipe  to  the  level  of  the  furface  of  the  ground, 
about  two  hogfheads  of  water  flowed  from  it  in  twenty- four 
hours,  which  liad  fimilar  properties  with  the  water  of  St.  Alk- 
mund's  well,  as  on  comparifon  both  thele  waters  curdled  a 
folution'  of  foap  in  fpirit  of  wine,  and  abounded  with  calca- 
reous earth,  which  was  copioufly  precipitated  by  a  folution  of 
fixed  alkali;  but  the  new  water  was  found  to  poffefsa  greater 
abundance  of  It,  together  with  numerous  imall  bubbles  of 
rlVial  acid  or  calcareous  gas. 

The  new  water  lias  now  flowed  about  twelve  months,  and,  as 
far  as  1  can  judge,  is  already  increaied  to  almoft  double  the  quan- 
tity in  a  given  time  ;  and  from  the  rude  experiments  I  made,  I 
think  it  is  now  lefs  replete  with  calcareous  earth,  approaching 
gradually  to  an  exact  correfpondence  with  St.  Alkmund's  well, 
as  it  probably  has  its  origin  between  the  lame  ftrata  of  earth. 


As  many  mountains  bear  inconteftible  marks  of  their  having 
been  forcibly  railed  up  by  fome  power  beneath  them ;  and 
other  mountains,  and  even  iflands,  have  been  lifted  up  by  fub- 
terraneous  fires  in  our  own  times,  we  may  fafely  reafon  on  the 
lame  fuppoiition  in  refpedt  to  all  other  great  elevations  of 
ground.  Proofs  of  thefe  circumftances  are  to  be  feen  on  both 
fides  of  this  part  of  the  country ;  whoever  will  infpe£l,  with 
the  eye  of  a  philofopher,  the  lime-mountain  at  Breedon,  on 
the  edge  of  Leicefierfhire,  will  not  heiitate  a  moment  in  pro- 
nouncing, that  it  has  been  forcibly  elevated  by  fome  power 
beneath  it ;  for  it  is  of  a  conical  form,  with  the  apex  cut  off, 

and 


{in  cirUficial  Spring  of  Water.  o 

and  the  ftrata,  which  compofe  the  central  parts  of  it,  and 
which  are  found  nearly  horizontal  in  the  plain,  are  raifed 
almoft  perpendicularly,  and  placed  upon  their  edges,  while 
thofe  on  each  fide  decline  like  the  furface  of  the  hill ;  fo  that 
this  mountain  may  well  be  reprefented  by  a  bur  made  by  forc- 
ing a  bodkin  through  feveral  parallel  flieets  of  paper.  At  Rou- 
ter, or  Eagle-ftone,  in  the  Peak,  feveral  large  mafies  of  grit- 
ilone  are  ieen  on  the  fides  and  bottom  of  the  mountain,  which 
by  their  form  evince  from  what  parts  of  the  fummit  they  were 
broken  off  at  the  time  it  was  elevated ;  and  the  numerous  loofe 
ftones  fcattered  about  the  plains  in  its  vicinity,  and  half  buried 
in  the  earth,  muft  have  been  thrown  out  by  explofions,  and 
prove  the  volcanic  origin  of  the  mountain.  Add  to  this  the 
vafb  beds  of  toad-flone  or  lava  in  many  parts  of  this  county, 
fo  accurately  defcribed,  and  fo  well  explained,  by  Mr.  White- 
hurst,  in  his  Theory  of  the  Formation  of  the  Earth. 

Now  as  all  great  elevations  of  ground  have  been  thus  railed 
,by  fubterraneoiis  fires,  and  in  a  long  courle  of  time  their  fum- 
mits  have  been  worn  away,  it  happens,  that  fome  of  the  more 
interior  ftrata  of  the  earth  are  expofed  naked  on  tiie  tops  of 
mountains;  and  that,  in  general,  thole  flrata,  which  lie  up- 
permoft,  or  neareft  to  the  fummit  of  the  mountain,  are  the 
loweft  in  the  contiguous  plains.  This  will  be  readily  con- 
ceived if  the  bur,  made  by  thrufling  a  bodkin  through  feveral 
parallel  fheets  of  paper,  had  a  part  of  its  apex  cut  off  by  a  pen- 
knife,  and  is  fo  well  explained  by  Mr.  Michell,  in  an  inge- 
nious paper  on  thePhasnomena  of  Earthquakes,  publifhcd  a  few 
years  ago  in  the  Philofophical  Tran factions. 

And  as  the^  more  elevated  parts  of  a  country  are  fo  much 
colder  than  the  vallies,  owing,   perhaps,  to  a  concurrence  ot 

two 


S  T)r,  Dar wind's  Account  of 

two  or  three  caufes,  but  particularly  to  the  lefs  condenfed  fmte 
:of  the  air  upon  hills,  which  thence  becomes  a  better  condu£lor 
■of  hiCat,  as  well  as  of  eleclricity,  and  permits  it  to  efcape  the 
fafler  ;  it  is  from  the  water  condenfed  on  thefe  cold  furfaces  of 
mountains,  tliat  our  common  cold  Iprings  have  their  origin  ; 
and  which,  (liding  between  two  of  the  ftrata  above  defcrlbed, 
•defccnd  till  they  find  or  make  themfelves  an  outlet,  and  will  la 
confequence  rife  to  a  level  with  the  part  of  the  mountain  where 
•they  originated.  And  hence,  if  by  piercing  the  earth  you  gain 
a  fpring  between  the  fecond  and  third,  or  third  and  fourth 
flratum,  it  mufl:  generally  happen,  that  the  water  from  the 
loweft  ilratum  will  rile  the  higheft,  if  confined  in  pipes,  be- 
'Caufe  it  comes  originally  from  a  higher  part  of  the  country  in 
its  vicinity. 

The  increafmg  quantity  of  this  new  fpring,  and  its  increafing 
purity,  t  fuppofe  to  be  owing  to  its  continually  diffolving  a 
part  of  the  earth  it  palles  through,  and  hence  making  itfelf  a 
wider  channel,  and  that  through  materials  of  lefs  folubility. 
Hence  it  is  probable,  that  the  older  and  flronger  fprings  are 
generally  the  purer ;  and  that  all  fprings  were  originally  loaded 
with  the  foluble  impurities  of  the  flrata,  through  which  they 
tranfuded. 

Since  the  above-related  experiment  was  made,  I  have  read 
with  pleafure  the  Ingenious  account  of  the  King's  wells  at 
Sheernefs,  In  the  laft  volume  of  the  Tranfadions,  by  Sir 
Thomas  Hyde  Page,  in  which  the  water  rofe  three  hundred 
feet  above  its  fource  in  the  well  ;  and  have  alfo  been  informed, 
that  in  the  town  of  Richmond,  in  Surrey,  and  at  Infhip  near 
Preflon  in  Lanca(hire,  it  is  ufual  to  bore  for  water  through 
a  lower  ftratum  of  earth  to  a  certain  depth  ;  and  that  when  it 

is 


an  artificial  Spring  of  Water,  j 

is  found  at  both  thofe  places,  it  rifes  lb  liigli  as  to  overflow  the 
furface  of  the  well :  all  thefe  fads  contribute  to  eftablifli  the 
theory  above-mentioned.  And  there  is  reafon  to  conclude, 
that  if  fimilar  experiments  were  made,  artificial  fprings, 
rifing  above  ground,  might  ia  many  places  be  thus  produced 
at  fmall  expence,  both  for  the  common  purpofes  of  life, 
and  for  the  great  improvement  of  lands  by  occafionally  water* 
ing  them. 


E    8    ] 


J  I.     .In  Accoimt  of  an  Engllfli  Bird  of  the  Genus   Motacllk, 
fuppofed  to  be    hitherto    unnoticed  by   Britifli    Ornithologijis ; 
obferved  by  the  Rev,  John  Llghtfoot,  M.  A,  F.  R,  S.    In  a 
J ,etter  io  Sir  Joieph  Banks,  Bart.  P.  R.  S. 


Read  November  1 8,   1784. 

SIR,  Uxbridge,  Nov.  20,    1783. 

AS  every  dilcovery  in  natural  hiftory  is  efteemed  worthy  the 
notice  of  that  Society  which  was  inftitiited  on  purpofe  to 
improve  natural  knowledge,  I  have  taken  the  liberty  to  fend 
you  a  defcription  and  drawing  of  a  bird  which  haunts  the 
reeds  of  the  river  Coin,  in  the  neighbourhood  of  Uxbridge, 
and  wliich  feems  to  have  hitherto  efcaped  the  notice  of  writers 
on  Britifh  Ornithology;  and  therefore  fome  account  and  de- 
fcription of  it  will  not,  I  trud:,  be  unacceptable  to  the  Society 
over  which  you  lb  laudably  prefide. 

The  neft  and  eggs  of  the  bird  I  am  about  to  defcribe  firjd: 
attrafted  my  attention,  and  led  to  the  difcovery  of  the  bird 
itfelf.  They  were  repeatedly  brought  by  a  fifherman  on  the 
Uxbridge  river,  in  the  parifh  of  Denham,  to  her  grace  the 
Duchefs  Dowager  of  Portland,  who  firft  communicated  them 
to  me.  They  were  fuppofed  by  the  fiflierman  to  belong  to  the 
Sedge-bird  of  Pennant,  or  MotacilU  Salicaria  of  Li  N  n^eu  s  ;  but 
being  well  acquainted  with  the  nefl  and  eggs  of  this,  I  was  very 
fure  he  was  miftaken,  though  he  actually  produced  this  bird  as 
the  true  proprietor  of  the  fubje6ls  in  queftion.  The  flru6lure 
and  pofition  of  the  nefb  having  a  fingular  appearance,  and  both 

that 


Mr»  Lightfoot''s  Account  of  a  new  Englifli  Bird,         ^ 

that  and  the  eggs  belonghig  to  a  bird  unknown  to  me,  I  became 
defirous  of  finding  out  the  fccret  architect,  and  to  that  end  made 
life  of  fuch  means  as  I  thought  mod  likely  to  promote  the? 
difcovery. 

Ill  a  fhort  time  my  expedations  were  gratified ;  for  on  the 
26th  day  of  July,  1783,  intelligence  was  brought  me,  that 
fuch  a  neil:  as  I  wanted  was  found.  I  had  given  pre- 
vious direction,  that  it  fliould  not  be  diiturbed  before  I  had 
leen  it.  Upon  examination,  I  inflantly  perceived  it  to  be  of 
the  fame  kind  and  flru£lure  with  that  under  enquiry,  contain- 
ing two  eggs,  and  two  young  ones  juft  excluded  from  the  fhell. 
One  of  the  old  birds  was  fitting  at  this  time  upon  the  neft, 
which  a  perfon  in  company  attempting  to  feize,  it  flew  at  him 
with  fo  much  refentment  and  acrimony,  as  to  draw  blood  from 
the  hand  that  dared  to  moleft  its  inflinclive  operations.  Both 
the  parent  birds  continued  hovering  about  their  neft  with  much 
watchful  care  and  anxiety,  while  I  made  feveral  attempts  to 
take  them  alive ;  but,  finding  all  endeavours  in  vain,  left  I 
(hould  lofethe  opportunity  of  examining  them  with  accuracy, 
I  at  length,  with  relu£lance,  caufed  them  to  be  (liot.  From 
thefe  fpecimens  the  following  defcriptions  were  made,  which, 
with  an  accurate  drawing  of  one  of  them,  together  with  its 
neft  and  egg,  are  humbly  fubmitted  to  your  notice. 

From  the  generic  chara(9:ers  delivered  by  LinnjEus,  our  bird 
m^ft  evidently  be  reduced  to  the  family  of  his  Motacilh,  for  it 
has  a  weak,  flender,  fubulate  bill,  almofi:  ftraight ;  the  man- 
dibles nearly  equal ;  the  noftrils  oval  and  naked,  or  not  covered 
with  briftles  ;  the  tongue  lacerated  at  the  extremity ;  the  legs 
{lender;  the  toes  divided  to  the  origin,  except  that  the  exterior 
one  is  joined,  at  the  under  part  of  the  lafl  joint,  to  the  middle 
toe  ;  the  claws  of  nearly  equal  length. 

Vol.  LXXV.  "  C  The 


ID  -W''  Light  foot's  Account  of    ■ 

The  male  and  female  have  the  fame  coloured  plumage,  fo 
that  one  delciiptlon  will  ferve  for  both.  They  differ  a  little  in 
fize,  but  their  external  appearance  is  the  fame.  They  are  both 
larger  than  the  Pettycbaps  defcribed  by  Willoughby  j  fmaller 
than  the  White-throaty  and  nearly  of  the  fame  lize  with  the 
JVilloW'Wren  ;  but  to  be  maore  particular. 

The  cock-bird  weighed,  when  jufl  killed,  exadly  (ewtn. 
pennyweights  and  nine  grains ;  the  hen  fix  pennyweights  and 
nine  grains,  or  one  pennyweight  lefs. 

The  males  meafured,  from  tip  to  tip  of  the  extended  wings, 
feven  inches  and  a  half;  the  female  fix  and  three-quarters. 

From  the  end  of  the  bill  to  the  extremity  of  the  tail,  th& 
cock  meafured  five  inches  and  a  half;  the  hen  only  five 
inches. 

The  bill  in  both  meafured  half  an  inch,  which  is  longer 
in  proportion  than  in  mofl:  of  this  genus.  The  tipper  mandi- 
ble is  of  a  dark  horn  colour,  (lightly  incurved  near  the  extre- 
mity, with  a  minute  indenture  on  either  fide  near  the  point ; 
the  lower  is  pale  red  or  flefh- coloured,  with  a  fhade  of  yellow  ; 
the  inlide  of  the  mouth  deep  orange-coloured ;  the  tip  of  the 
tongue  cloven  and  ciliated  ;  the  noflrils  oval,  and  deflitute  of  a 
briftly  covering ;  but  at  the  bafe  of  the  upper  mandible,  on 
either  fide,  near  the  angle  of  the  mouth,  arife  three  fhort  vi- 
b7'iffce  pointing  downwards,  black  at  their  fummits,  white  at 
their  bales ;  a  circumfl:ance  common  to  many  others  of  this 
genus.  The  iris  of  the  eye  is  olive-brown ;  the  pupil  black. 
The  fhort  feathers  of  the  orbits  or  eye-lafhes  are  of  a  dirty 
white  colour.  From  the  corner  of  each  eye  to  the  noflril  is  a 
broad  flroke  or  band  of  tawny-white  feathers,  lying  ov^er  each 
other,  and  running  narrowefl:  towards  the  bill ;  this  affords  an 
excellent  mark  to  diftinguifh  the  fpecies^ 

The 


a  ficw  ^ngWih  Bird.  ji: 

♦  The  feathers  of  the  head,  neck,  back,  coverts  of  tiie  wings  nr.d 
rump,  are  of  an  olive-brown,  with  a  flight  tinge; of  green.  The 
quill  and  tail  feathers  are  all  of  a  darker  hue,  orfimply  brown  ; 
their  outward  edges  of  a  paler  fhadc.  The  tall  is  two  inches. 
long,  nightly  cuneated,  the  middle  feathers  being  a  little  longer 
than  the  reft,  the  others  gradually  fliorter  ;  all  of  one  uniforin 
(kin-brown  colour  edged  with  paler  brown,  and  a  little  wedge-- 
fhaped  at  their  ends.  -         .  ;   .fj[ 

The  chin  is  white ;  the  throat,  breafl,  belly,  and  parts  about' 
the   vent,  are  white  with  a  (light  fhade   of  buff  or  tawny  -, 
but  all  thefe  feathers  (as  in  feveral  others  of  this  genus)  when 
blown  afunder,  or   clofely  examined,  are  found  to  have  their 
bafe  or   lower    half    black,    except   the    fhafts,    which  .are' 
white  throughout,  .:rj 

,  The  ridge  and  under  coverts  of  the  exterior  angle  of  the 
wing  are  of  a  yellowifh-tawny  colour,  as  are  alfo  the  feathxcrs 
of  the  thighs  ;  but  thofe  of  the  knees  are  a  fhade  darker,  or  a 
pale  yellowilh  brown. 

The  legs  arc  a  light  olive ;  the  foles  of  the  feet  bright  yel- 
low, with  a  tinge  of  green,  which  foon  fades  after  the  bird  is 
dead.  The  inflep  is  covered  with  feven  large  imbricated  fcalesy> 
and  five  fmaller  on  the  toes,  as  in  others  of  the  genus.  The 
toes  {land  three  before,  and  one  behind  ;  the  claws  are  nearly 
of  equal  length  and  curvature;  but  the  hindmofl:  is  thickefl 
and  itrongefl. 

From  the  foregoing  remarks  it  is  evident,  that  the  bird  men- 
tioned is  a  fpecies  of  Moladlla,  which,  as  I  can  find  no  fucli 
defcribed  by  any  fyftematic  writer,  I  fliall  venture  to  name, 
after  the  Linnjean  manner, 

Motacilla  {arundinaced)  fupra  olivaceo-fufca,  fubtus  al'bida, 
lori?  ^t  Qrbitis  fufco-albefcentibus,  aagulo  carpi  fubtus 

C  ^  luteo- 


12  Mr,  Lightfoot's  Account  of 

Juteo-fulvo,    Cauda    fubcuneata    fufea,    plantis    luteo- 
virefcentibus. 

In  regard  to  fynonyms,  the  only  author  I  can  find  who  can 
be  fufpeded  of  having  noticed  this  bird  is  Sepp,  who,  in  a  late 
fplendid  work,  in  the  Dutch  language,  Intituled,  Nederl'andfche 
Vogelen  ffol.  chart. max,)  p.  i  o  i ,  has  defcribed  and  figured  a  bird, 
under  the  name  of  Turdus  arundinaceus  minimus^  called .  in  Hol- 
land Karrakietje,  which  in  many  refpe£ls  agrees  with  our  bird  ; 
but  as  the  colour  of  the  wings  in  that  figure  is  made  a  reddifh 
brown,  inflead  of  an  olive-brown,  and  the  tawny- white  Lor  a 
(a  moft  effential  chara^lier  to  diflinguifh  the  fpecies)  are  not  at 
all  exprefled  j  and  the  eggs  are  made  to  be  of  a  pale-blufh  colour 
with  dark  fpots,  inftead  of  a  dirty-white  with  olive  fpots ;  I. 
cannot  pronounce  for  certain,  that  the  bird  there  intended  by 
that  writer  is  the  fame  which  we  have  now  defcribed;  though, 
if  fome  allowance  be  made  for  ill- colouring,  and  other  omif* 
iions,  it  may  poffibly  have  been  ddigned  for  the  fame  fpecies. 

As  we  have  already  a  bird,  called  In  Engllfli.  the  Willow^ 
wren  ;  ours,  being  nearly  of  the  fame  lize  and  fhape,  as  well  as 
the  fame  genus,  may,  from,  its  haunts,  not  improperly  be 
denominated  the  Reed-wren. 

It  frequents  the  banks  of  the  river  Cola  near  Uxbridge,  as . 
far  as  from  Harefield-Moor  down  to  Iver,  about  the.  fpace  of. 
five  miles,  and  very  probably  moil  other  parts  of  the  fame..= 
river,  though  not  as  yet  obferved. 

It  is  alfo  certainly  found  in  the  neighbourhood  of  Dartford 
in  Kent,  from:whence  a  nefl  -and  eggs  were  communicated  by . 
the  ingenious  Mr,.  Latham  of  that  place,  but  without  knoww. 
ledge  of  the  bird  to  which  they  belonged ;  fo  that  there:  is 
little  doubt  but.  that  it .  may  .be  found  in  many  parts  of  the 


kingdom. 


Its 


a  new  Engllfh  Btr^,  12 

Its  food  Is  infedls,  at  leaft  in  part,  for  I  obferved  it  catching 
flies.  It  hops  continually  from  fpray  to  fpray,  or  from  one 
reed  to  another,  putting  itfelf  into  a  ftooping  pofture  before  it 
moves.  1  heard  it  make  no  other  than  a  fingle  note,  not  un- 
like the  found  of  the  word  peep,  uttered  in  a  low  plaintive 
tone ;  but  this  might  probably  be  only  a  note  of  diftrefs,  and 
it  may  have,  perhaps,  more  pleafing  and  melodious  ones  at 
other  times,  with  which  I  am  unacquainted. 

The  neft  of  this  bird  is  a  moft  curious  flru6lure,  unlike  that 
of  any  other  I  am  acquainted  with,  enough  to  point  out  the 
difference  of  the  fpecies,  if  every  other  charader  was  wanting. 

It  may  not  be  amifs  here  to  obferve,  that  there  is  fuch  a' 
manifefl  diverfity  in  the  materials,  locality,  and  formation  of 
nefts,  and  fuch  variety  of  colours  in  the  eggs  of  many  birds 
(in  other  refpe6ts  hard  to  be  diftinguiflied),  that  it  is  pity  this 
part  of  Ornithology  has  not  been  more  attended  to.  I  am  well 
convinced,  that  as  many  fpecies  of  infedis,  nearly  allied  to  each 
other  in  colours  and  fhape,  and  reputed  to  be  only  i;^r/V//V/,  are 
frequently,  from  a  due  attention  to  their  larvae  (which  are  often 
extremely  different),  difcovered  to  be  fpecies  totally  diflindt ;  fo, 
amongft  birds-  of  fimiiar  genus  and  feather,  their  true  differences 
may  be  often  found  by  carefully  obferving  their  nefts  and  eggs,, 
when  other  characters,  are  fo  miimte,  in  the  birds  themfelves,. 
as  .to  be  diftingullhed  with  difficulty.  By  experience  I  have 
found  this  to  be  remarkably  verified  in  fome  of  the  Lark  kind.  - 
But  to  return  to  the  neff.  I  was  going  to  defcribe.  It  is  com- 
pofed  externally  of  dry  flalks  of  grafs,  lined,  for  the  mofl 
part,  with  the  flowery  tufts  of  the  common  reed,  or  Arundo 
'Dallatoria,  but  fometimes  with  fmall  dead  gralles,  and  a  few 
black  horfe-hairs  to  cover  them.     This  neft  is  ufually  found 

fufpcnded 


14  Mr,  LiGHtFOoT's  Account  of 

fyfpfended  or   faftened  on,- like  a  hammock,  between  three -or 
four  fl'alks  of  reeds,  below  the  panicles  of  -flowers,  in  fueh  a 
manner  that  the  ^flalks  run  •  through  the  fides  of  the  nefts'  stt 
nearly  equal   dlftances  ;  or,'  to  fpeak  more  properly,^  the  i^'efl^ 
Jb  tied -on  to  the  rfeeds  with^^i?^(^^r^j-,'sn-dfometiiiaes  {as  beiftg^ 
mSfe  eligible'  when'' ?t -can  be  had)  eVeil'  with  thread  iM\di  pack-'^- 
/j6rf^<3',''emiil3ting'thfe  work  of  a  fempftrefs,  as  was  the  cafe  of" 
the  nelt  exhibited  in  the  drawing.     The  bird,  however,  though 
generally,'  does  ilot  always  confine  her  building  to  the  fupport 
df  reeds;  fometimes   flie  fixes  it  on  to  the  branches  of  thc^ 
lVater^dock\  and,  in   one  inftance  only  (that  here  delineated), 
it  was   found  faftened  to  the  trlfurcated  branch  of  a  SyrtngOt 
bufh,  or  Philadelphia^  growing  in  a  garden  hedge  by  the  river ' 
fide.' 

She  lays  commt)nly  four  eggs';  the  ground  colour  a  dirty 
white,  ftained  all  over  with  dull  olive-coloured  fpots,  but 
chiefly  at  the  greater  end,  where  are  generally  ittn  two  or 
three  fmall  irregular  black  fcratchcs ;  but  thefe  are  fometimes 
fcarcely  viflble. 

I  muft  not  omit,  that  both  "the  neft  and  eggs  which  I  have 

no^  defcribed,  whether  defigned  for  the  fame  or  not,  are  well 

exprefled  by  Sepp,  in  the  work  above  cited,  under  the  article 

iJurdus  Calamoxenus,  or  Rietvhick,  p.  gj.-,  but  as  the  bird  there 

reprefented  is  evidently  the  Motacilla  Sylvia,  Lin.  or  common 

White-throat  (which  is  known  to  make  a  very  different  nefl),  I 

am  inclined  to  believe,  that  the  author,  by  miflake,  placed  a 

bird  and  nefl  in  the  fame  plate  which  do  not  belong  to  each 

other. 

J  have  reafon  to  think,  that  the  bird  I  have  been  charac- 

.teriz.iiig  is  a  bird  of  migration ;  for  the  inhabitants  on  the  iides 

2  of 


rii,i^,Tn,„>  r.  /./.xxi'ui)  \./,  14. 


a  new 'EngWih  Birc^,  15 

of  the  Coin  do  not  recolle£l  ever  to  have  feen  it  in  the  winter 
months ;  and  its  food  being  infers,  it  is  probable,  it  muft  be 
obliged  to  fhift  its  quarters  for  a  warmer  climate  at  the  ap- 
proach of  a  {eveti  feafon ;  bat  this  at  prefent  is  only  matter  of 
conjedlure,  and  not  certainty. 


I  am,  &c. 


JOHN  LIGHTFOOT. 


t    '6    3 


III,  Aa  Recount  of  Morne  Garqu,  4i  Mountain  tn  the  IJland  tf 
St.  Vincent,  with  a  JOefcription  of  the  Volcano  on  its  Summit, 
In  a  Letter  from  Mr,  James  Anderfon,  Surgeon^  to  Mr. 
Forfyth,  His  Majejlfs  Gardener  at  Kenfington ;  communis 
cated.  by  the  Right  Honourable  Sir  George  Yonge,  Bart. 
W*  R.  S, 


Read  November  i8,  1784, 

THE  many  ridges  of  mountains  which  interfed  this  ifland 
in  all  directions,  and  rife  in  gradations,  one  above  the 
other,  to  a  very  great  height,  with  the  rivers  tumbling  from 
their  lides  over  very  high  precipices,  render  it  exceeding  difficult 
to  explore  its  interior  parts. 

The  moft  remarkable  of  thefe  mountains  is  one  that  termi- 
nates the  N.VV.  end  of  the  ifland,  and  the  higheft  in  it,  and 
has  always  been  mentioned  to  have  had  volcanic  eruptions  from 
it.  The  traditions  of  the  oldeft  inhabitants  in  the  ifland,  and 
the  ravins  at  its  bottom,  feem  to  me  to  vindicate  the  aflertioii 
As  I  was  determined,  during  my  ftay  in  the  ifland,  to  fee  as 
much  of  it  as  I  could ;  and  as  I  knew,  from  the  altitude  of 
this  mountain,  there  was  a  probability  of  meeting  with  plants 
on  it  I  could  find  in  no  other  part  of  the  ifland  ;  I  fliould 
have  attempted  going  up  if  I  had  heard  nothing  of  a  volcano 
being  on  it.  But  viewing  the  mountain  at  a  difl:ance,  the 
ftrufture  of  it  was  different  from  any  in  the  ifland,  or  any  I  had 
feen  in  the  Wefl  Indies.  I  could  perceive  it  divided  into  many 
2  different 


Mr.  Anderson's  Account  of  a  Volcanic  MouHiain^  6cc,     ty 

different  ridges,  feparated   by  very  deep  chafms,  and  its  fum- 
mit  appeared  quite  deflitute  of  any  vegetable  produ£lion.     On 
examining  leveral  ravin s^  tliat  run  from  the  bottom  a  great  way 
up  the  mountain,  I  perceived  they  were  quite  deftitute  of  water, 
and  found  pieces  of  pumice-ftone,  charcoal,  feverai  earths  and 
minerals,  that  plainly  indicated  there  mufl:  be  fome  very  fingu- 
lar  place  or  other  on  fome  part  of  the  mountain.     I  alfo  recol- 
leded   a  flory  told  by  fome  very  old  men  in   the  ifland,  that 
they  had   heard  the  captain  of  a  (hip  fay,  that  between  this 
ifland  and  St.  Lucia  he  faw,  towards  nieht,  flames  and  fmoke 
ifiliing  from  the  top  of  this  mountain,  and  next  morning  his 
decks   were  covered  with  afl'ies  and  fmali  ftones.     This,  you 
may  readily  imagine^  was  excitement  enough  to  examine  it,  if  1 
pofiibly  could  ;  but  I  was  much  difcouraged   upon  being  told, 
it  was  impoflible  to  gain  the  fummit  of  it;  nor  could  I  get 
cither  white  men,  Carribbee,  or  Negro,  that  would  undertake 
to  conduct  me  up  for  any  reward  I  could  offer ;  nor  could  I  get 
any  information  relative  to  it.     But  as  difficulty  to  attain  in- 
hances  the  value  of  the  obje-fl,  fo  the  more  I  was  told  of  the 
impoflibility   of  going   up,    the  more  was   I   determined  to 
attempt  it. 

After  I  had  examined  the  bafis  of  it,  as  far  as  I  could  for  the 
fea  and  other  mountains,  to  find  the  moft  probable  place  to 
commence  my  journey,  I  obferved  an  opening  of  feverai  large 
and  dry  ravins,  that  leemingiy  ran  a  great  way  up  ;  but  I  was 
not  fure  if  they  were  not  interfered  by  fome  rocks  or  preci- 
pices I  could  not  get  over.  I  came  to  Mr.  Maloune's,  about 
a  milediftant  from  the  mountain,  but  the  nigheft  houfe  to  it 
I  could  flay  at  all  night.  Here  I  met  with  a  friendly  recep- 
tion and  great  hofpitality.  After  communicating  my  inten- 
tions to  him,  he  told  me,  he  would  give  me  every  afliftance 
Vol.  LXXV.  D  he 


l8  Mr.  Anderson's  Account  of  a 

he  could,  by  fending  fome  trulliy  negroes  with  me,  and  wiihed' 
he  was  able  to  go  with  me  himfelf.     This  was  a  kind  offer  to 
ine,  in  my  then  fituation,  as  negroes  were  what  I  only  wanted, 
having  only  one  boy  belonging  to  Dr.  Young  with  me.     I 
knew,  if  I  had  great  difficulties  in  the  woods,  he  and  I  both 
fhoujd  be  inadequate  to  the  talk,  as  in  a  fhort  time  we  fhould  be 
ic  wearied  as  to  be  unable  to  proceed  :  from  what  I  had  feen  of 
the  mountain,  I  knew  I  muft  be  tuider  the  neceffity  of  carrying- 
water  with  me;  and  from  the  great  diftance  to  the  top,  and' 
obitrudions    w^e  might  naturally    expe6l,    I    fhould    at    leaft 
require  two  days  to  accomplifh  it. 

By  examining  the  fide  of  the  mountain  towards  me  with  a 
good  glafs,  I  imagined  I  faw  two  ridges  1  might  get  up.  I  per- 
ceived they  were  covered  great  part  of  the  way  with  thick 
wood;  yet  1  hoped,  with  a  little  cutting,  I  fliould  be  able  to 
,  fcramble  through  them.  I  appointed  next  morning  to  begin, 
my  route  by  one  of  thefe  ridges. 

February  26,   1784,  I  left  Mr.  Maloune's  about  fun-rife,, 
with  two  flout  negroes  and  Dr.  Young's  boy  ;  each  of  us  hav- 
ing a  good  cutlafs,  as  well  to  clear  our  way  through  the  woods, 
as  to  defend  us  in  caf6  we  fhould  be  attacked  by  Carlbbees  or/ 
run-away  negroes.     We  arrived  at  the  bottom  of  the  mountain 
a  little  before  {tVQU.  in  the  morning.     To  get  to  either  of  the^ 
ridges,  we   found   we  had  a  rock  to  climb  above  forty   feet 
high:  it  was   with   great  difficulty  we   fcrambled  up,    affifl-?- 
ing  one  another  in  the  befl  manner  we  could  ;  here  we  found  it' 
neceiihry  to  contra<!:l:  our  baggage.     After  getting  up  this  rock,. 
I  found  myfelf  in  the  bottom   of  a  narrovy  and -deep  ravin.. 
Having  afcended  this   ravin   a  little  way,  I  faw  fome  cleared , 
ground  on  Its  fides,  with   tobacco  growing.     This  I  conjec- 
tured: was  the  habitation  of  fome  Caribbees;  but  I  was  much, 

^:  .  furprifed 


Volcanic  Mountain  in  St.  Vincent's.  iq 

furprifed  when  one  of  the  negroes  I  had  with  me  told  me,  it 
was  the  habitation  of  a  Mr.  Gasco,  a  Frenchman.  What 
could  induce  a  ftout  healthy  man  in  the  prime  of  life,  and  a 
good  mechanick,  with  feveral  negroes,  to  take  up  his  refidence 
among  rocks  and  precipices,  excluded  from  the  whole  world, 
is  a  my  fiery  to  me.  Befides,  by  ev^cry  torrent  of  rain  that 
happens,  he  may  expe6t  hlmfelf  and  all  his  habitation  to  be 
wafhed  over  the  rocks  into  the  ocean.  Notwithftanding  his 
fingular  fituation,  I  found  him  an  intelligent  man^  and  I  expe- 
rienced every  hofpitality  his  poor  cottage  could  afford. 

The  difficulty  of  going  through  woods  in  the  Weft  Indies, 
where  there  are  no  roads  or  paths,  is  far  beyond  any  thing  an 
European  can  conceive.  Befides  tall  trees  and  thick  under- 
wood, there  are  hundreds  of  different  climbing  plants  twifted 
together  like  ropes,  and  running  in  all  diredions  to  a  great  ex* 
tent,  and  even  to  the  tops  of  the  higheft  trees ;  by  pufhing  on 
they  cannot  be  broke,  and  many  of  them  with  difficulty  cut ; 
befides  a  fpecies  of  grafs,  the  Schoenus  Lithofpermos,  with  fer- 
rated  leaves,  that  cuts  and  tears  the  hands  and  face  terribly. 
With  fuch  obftruclions  as  thefe  it  was  above  two  hours  before 
we  got  on  the  ridge,  where  I  was  in  hopes  our  paffage  would 
have  been  eafier ;  but  I  foon  found  my  miftake,  for  I  was  fur- 
rounded  with  a  thick  foreft,  much  more  difficult  to  get  through 
than  before,  on  account  of  the  large  piles  of  trees  broken  down 
by  the  hurricanes,  to  pafs  which  in  many  parts  we  were  obliged 
to  creep  on  our  hands  and  feet  to  get  below  them,  and  in  other 
places  to  climb  a  great  height  above  the  furface  of  the  ground, 
to  get  over  large  trunks  lying  on  one  another,  and  thefe  being 
frequently  rotten,  occafioned  us  to  tumble  headlong  down  to  a 
great  depth,  among  rotten  wood  and  grafs,  fo  that  it  was  with 
great  difficulty  I  and  the  negroes  could  extricate  ourfelves.     By 

D  2  con- 


r^o  M>"-  Andersojs's  Account  qJ  a 

^onftaiitly  cutting  to  clear  our  way,  I,  as  well  as  D^^y  compa- 
nions,  grew  much  tatigued,  and  they  wilh^d   much  to  return 
back.     About  four  in  the  afcernoou  \  could  not  prevail   upon 
them  to   proceed  farther ;  if  they  did,  tlicy   could  not  return 
before  dark,  and  they  would  not  deep  all  night  in  the  woods; 
but  laid,  if  I  ftayed  they  would  return  to  me  next  morning.     I 
faw  it  was  impoffible  to  gain  the  iummit  of  the  mountain  with 
the    boy    only  by  that    route :    I    likewife    faW'   the    woods 
orowing;     more   difficult,     mv   w^ater   alfo    totally   expended  : 
from  thefe  conliderations  I  intended  to  go  down  to  the  French- 
man's, and  remain  there  all  night,  and  try  another  route  with 
my  boy  next  morning,  hoping  I  might  be  fortunate  enough  to 
find  an  eaher  pafiage.     I  arrived  at  Mr.  Gasco's  a  little  after 
fun-fet,  being    m.uch   fatigued  and   thirfly,    and  never  expe- 
rienced more  hofpitality  and  kindnefs-  than  from  this  man  rii 
his  miferable  cot ;  for  we  ought  not  to  judge  of  the  value  of  the 
things  received,  but  of  the  difpolition  of  t,he  heart  with  which 
they  are  given.  He  parted  with  his  hammock  to  me,  and  flept  oil 
^  board  hirnfelf.     This  I  at  firft  refufed ;  but  he  infjfted  on  it, 
telling  me,  from  my  hardfhips  of  the  day  I  was  much  more 
tired  than  he.  I  took  the  hammock,  but  I  found  it  was  impoiliblc 
to  clofe  my  eyes   during  the  night  with  cold.     His  hut  w'as 
built  of  rofcaux  or  large  reeds,,  between  each  of  which  a  dog 
might  creep  through,  and  the  top  was  covered  with  dry  grafs. 
It   is  fituated  in  the  bottom  of  a  deep  gully,,  where  the  fun 
does  not  ihine  till  nine  in  the  morning,  nor  after  four  in  the: 
afternoon.     It  is  furrounded  by  thick  wood,  /and  during  the 
night  the  whole  of  the  mountain  is  covered  with  thick  clouds, 
Irom  which  it  frequently  rains ;  this  makes  the  night  air  cxr 
ceedingly  cold.     I  got  ready  to  renew  my  journey  next  morn- 
ing, hav^iug   only  Dr.  Younq's  boy  with  ixie,  who  continued 

\  very 


Folarnic  Mountain  in  St.  Vincent's.  li 

4fery  faithful  to  me  during  this  excurfion,  being;  very  active  and 
hardy:  I  do  not  knov/  it  I  could  have  gone  through  this  fa- 
tigue had  it  not  been  for  his  affifl'ancc.  1  now  determined  to 
commence  this  day's  route  up  the  ravin,  as  it  feemed  to  widen 
and  apparently  run  a  confiderable  way  up  in  the  direction  i 
wifhed  for;  and  if  I  conld  get  out  of  it  upon  the  other  ridge, 
it  would  at  leafl  be  two  miles  nearer  than  the  way  I  had  at- 
tempted yefterday,  and  probably,  after  getting  out  of  it,  I 
might  find  wood  eafier  of  accefs.  In  this  ravin  I  got  up  about 
a  mile  and  a  half,  without  meeting  with  any  conhderable  ob- 
flru6tion.  Encouraged  by  getting  fo  fiir,  although  the  ravin, 
was  narrowing  faft,  with  numbers  of  rocks  and  precipices  to= 
climb  over,  w^ith  vines  and  bullies  difficult  to  get  through,  I 
was  refolved  to  periifl  in'  this  route,  and  determined  by  every 
poffible  means  to  get  to  the  objedl  of  my  wifbes,.  well  knowing 
if  I  could  not  perform  it  this  way,  I  might  abandon  it  entirely,. 
After  climbing  over  a  number  of  difficult  paffes,  the  ravin  ter- 
minated at  the  bottom  of  a  very  high  precipice ;  how  far  it 
was  to  the  fumimit  I  did  not  know,  being  covered  toward  the 
top  with  thick  wood ;  but  from  the  bottom  upwards  it 
was  loofe  fand  as  for  as  I  could  fee,  with  ferns  and  tufts  of 
grafs,  which,  as  foon  as  I  took  hold  of  them,  came  out 
at  the  roots.  The  precipice  being  fo  very  flieep,  with  no  trees 
or  buffies  on  it  to  affift  tnQ  in  getting  up,  I  plainly  faw  the  at- 
tempting to  climb  it' was  at  the  rilk  of  my  life:  however,  I 
was  refolved  to  try  it,  and  telling  the  boy  to  keep  fome  diftance 
behind  me,  in  cafe  I  ffiould  tumble  and  drive  him  down  along 
with  me,  I  began  to  afcend,  holding  the  tufts  cf  grafs  a-s 
lightly  as  poflibie,  and  digging  holes  with  my  cutlafs  to  put 
my  feet  in  ;  but  I  often  loft  my  hold,  and  frequently  Hipped 
dowu  a  confiderable  diftance  ;  however,  as  it  was  nothing  but- 

loofe 


"22  .  Mr.  Anderson's  Account  of  ti 

loofe  f-aaJ,  I  could  eafily  pufli  my  'cutlafs  into  it  to  the  handle/ 
and  by  gi'^^phig  it  could  recover  myfelf  again.     Had   I   not 
taken  the  refolution  before  1  began  to  afcend  to  diveft  myfelf  of 
fear,  I  could  not  poffibly  have  gone,  for  the  terror  of  falling 
would  have  been  the  means  of  it  every  inftant.     I  got  up  to 
fome  wild  plantains,  which  I  faw  continued   all  the  way  to 
the  place  where  the  bufhes  and  trees  began  tto  grow.     I  here; 
refted  myfelf,  and  waited  for  the  boy's  getting  to  me,  which 
he  did  much  eafier  than  I,  although  he  had  the  provilions  and 
water,  owing  to  the  track   I    had  made,  and  becaufc,  being- 
much  lighter,  he   could  better  trufl:   himfelf  to  the  grafs  and 
ferns.     After  fome  labour  we  arrived  at  the  top  of  the  preci- 
pice.    I  found  myfelf  on  a  very  narrow  ridge,  thickly  covered 
with  wood,  and  bounded  by  two  ravins,  the  bottoms  of  which 
I  could  not  fee  ;  the  defcent  to  them  feemed  to  be  nearly  per- 
pendicular, yet  all  the  way  covered  with  thick  wood.    After  re- 
frefhing  ourfelves,  we  began  our  fatigue,  the  boy  and  I  cutting, 
and  carrying  our  water  and  provilions,  alternately.    When  we 
had  got  fome  way,  I  found  Iwas  on  an  exceeding  narrow  ridge, 
•in  many  parts   not  fix   feet  broad;  on  each  fide  a  tremendous 
gulf,  into  one  or  other  of  which  I  was  often  in  danger  of  fal- 
ling, fo  that  with  great  caution  I  was  obliged  to  lie  down  on 
my  belly,  to  fee  through  the  bufhes  how  the  ridge  tended.  Here 
I  began  to  fmell  fulphur,  or  rather  a  fmell  like  gunpowder. 
As  I  knew  this  fmell  mufl  come  from  the  top  of  the  mountain, 
being  in  the  direction  of  the  wind,  1  was  in  hopes  we  could 
not  be  far  from  it,  as  the  fmell  grew  ftrongerandftronger  as  I 
afcended.     I  faw  a  rifing  before  me,  and  thought  if  I  was  once 
on  it,  if  the  top  of  the  mountain  was  near  1  could  have  a  view 
of  it ;  but  having  got  on  this  rifing  I  could  only  fee  a  high  peak 
®n  the  N.W.  end  of  the  mountain,  andby  appearance  1  thought 
^  myfelf 


Fblcan/c  Alountain  in  St.  Vincent's.  23^ 

myfelf  very  little  nearer  than  when  I  was  at  the  hottom.  The 
woods  now  became  very  difficult  to  get  through  ;  great  quan- 
tities of  fallen  trees  lying  buried  under  long  grafs  and  being 
rotten,  when  I  thought  myfelf  walking  on  the  ground,  I  was 
frequently  buried  a  great  depth  among  them.  Being  now 
about  noon,  and  my  turn  to  carry  the  baggage,  and  confe- 
quently  my  turn  of  reft,  I  was  furprifed  to  hear  a  ruftling 
among  the  bufiies,  and  fomething  like  a  human  voice  behind 
me.  As  we  were  now  in^aplace  where  I  had  little  reafon  to 
fuppofe  there  had  been  a  human  foot  before,  and  could  not 
imagine  there  could  be  habitations  of  Caribbees  or  run- away 
negroes,  iince  from  the  barrennefs  of  the  mountain  they 
could  notpoffibly  find  any  provifions  to  fubfift  on,  I  told  the  boy 
to  ftandflill,  and  let  us  wait  their  coming  up;  for  if  they  were 
Garibbees  advancing  with  an  intention  to  hurt  us,  there  was  no 
alternative  but  to  defend  ourfelves.  You  may  imagine  my  fur- 
prife  when  I  faw  one  of  the  negroes  who  had  been  with  me  the 
day  before,  with  three  others,  which  Mr.  Maloune  had  fen t 
to  my  affiilance,  with  plenty  of  provifions.  After  rcfrefh- 
ment,  with  this  afliftance,  I  renewed  my  labours  with  frefh 
fpirits,  and  thought  I  was  fure  of  reaching  the  top  before 
night.  Having  proceeded  a  little,  I  had  a  fair  view  of  the 
ravin  on  my  left,  which  was  of  prodigious  depths  and  ran 
from  near  the  top  of  the  mountain  to  the  fea ;  its  bottom 
feemed  to  be  a  rock  of  a  colour  nearly  refembling  lava,  and 
appeared  as  if  there  had  been  vafl  torrents  of  fulphureous  mat- 
ter running  in  it  feme  time.  I  regretted  much  I  knew  not  of 
this  ravin  before  I  commenced  my  excurfion,  as  by  paffing  a 
head-land  in  a  canoe,  and  getting  Into  the  ravin,  I  might  have 
gained  the  fummit  of  the  mountain,  without  experiencing  the 
delays  and  difficulties  I  here  encountered.     It  was  now  about 


24.  Mr,  AndeHSoj^'s  Jccouni  of  a 

4  P.M.  au'i  I  had  no  profpe6l  of  the  mountain's  top  ;  but  itcrn 
the  afcent  of  the  ravin  below,  1  knew  it  was  a  great  way  oit.  I 
thought  if  I  could  get  into  the  ravin  before  night,  I  could  gec 
eafily  up  next  morning.  After  cutting  a  great  way  througii 
wild  plantains,  the  fun  near  fetting,  I  found  myfelf  almoU: 
over  the  verge  of  a  precipice  :  by  catching  hold  of  Ibme  ilirub^ 
I  prevented  myfelf  from  falling.  We  were  now  about  half- 
wav  down  ;  but  all  the  way  below  us,  as  far  as  we  could  fee, 
was  a  perpendicular  precipice  of  rock,  feveral  hundred  feet 
high*  to  pafs  which  was  impofllble.  I  had  a  view  of  fome  part 
of  the  top  of  the  mountain,  which  I  law  was  yet  far  from  me  ; 
nor  could  I  attempt  any  other  way  than  the  ridge  I  had  left. 
Being  now  fun-fet,  and  the  negroes  very  difcontented,  becaufe 
they  could  not  return  that  night,  I  found  we  mitft  take  up  our 
night's  refidence  in  the  place  where  we  were.  It  was  a  very 
tmfavourable  one,  there  being  nothing  but  plantains  growing, 
which  retaining  the  rain  iongln  their  leaves,  and  being  frequently 
agitated  by  the  wind,  were  conflantly  dropping,  and  kept  the 
ground  always  moift.  Being  almoft  dark,  we  had  time  to  make 
us  no  other  habitation,  than  placing  two  or  three  fticks  againft 
an  old  fiump  of  a  tree,  and  flightly  covering  them  with  plantain 
leaves.  After  getting  together  fome  little  wood  to  make  a  fire 
to  keep  us  comfortable,  it  began  to  blow  and  rain  violently, 
which  continued  ail  night.  We  foon  found  our  building 
afforded  us  no  fhelter,  and  the  wood  would  not  burn,  fo  that 
we  could  not  get  any  fire  ;  and  the  ground  on  which  we  were 
Situated  would  not  allow  the  leafl  exercife  to  keep  us  warm# 
From  fuch  a  miferable  night  I  experienced  no  mitigation  for 
the  fatigues  of  the  day.  I  wiflied  for  the  riling  fun,  to  renew 
4jiy  labours^  \vhich  I  at  laft  beheld  with  inex.prefiible  joy, 

As 


VoiciUtic  Mountain  In  St.  Vincent's-  35 

As  foon  as  wc  could  fee,  we  returned  to  the  ridge  \vc  left 
the  night  before,  and  began  to  work  with  alacrity,  as  we  were 
rhnofl:  chilled  with  cold.  I  puihed  on  as  fall  as  podlble,  and 
about  ten  o'clock  found  the  woods  began  to  grow  thin.  1 
could  not  fee  the  top  of  the  mountain,  but  had  a  view  of  fe- 
vcral  ridges  that  joined  it.  F^om  tlie  wind  flilHng,  and  the 
heat  growing  intenfe,  I  thought  we  muft  then  be  under  tlie 
cover  of  the  fummit :  I  here  found  many  new  plant;;.  About 
eleven  A.M.  I  was  overjoyed  to  have  a  full  view  of  the  fummit 
of  the  mountain,  nearly  a  mile  diftant  from  us,  and  that  we 
were  nearly  out  of  the  woody  region.  The  top  feemed  to  be 
compofed  of  fix  or  feven  ditferent  ridges,  very  much  broken  in 
the  fides,  as  If  they  had  fuffered  great  coavulfions  of  nature  ; 
they  were  divided  by  amazing  deep  ravins,  without  any  water 
in  them.  I  obferved  where  the  rklges  meet  the  edge  of  a  large 
excavation,  as  it  feemed  to  be,  on  the  higheft  part.  I  imagined 
this  might  be  the  mouth  of  the  crater,  and  dire.rred  my  courfc 
to  a  high  peak  which  overlooked  it.  I  found  here  a  moft 
beautiful  tree  which  compofed  the  latl:  w^ood.  After  that  I  en- 
tered into  a  thick  long-  jrrafs,  intermixed  with  fern,  which 
branched  and  ran  in  every  direction.  To  break  it  was  impof- 
fible,  and  wdth  great  difficulty  I  could  cut  it ;  {q  that  in  clear- 
ing our  way  through  this  grafs,  eight  or  ten  feet  high,  there  was 
equal  difficulty  as  in  the  woods,  and  it  feemed  to  continue 
very  near  to  the  top  of  the  mountain.  Being  now  about  noon,  I 
and  the  negroes  were  fo  fatigued  as  hardly  to  be  able  to  ftand  ; 
our  thirft  very  great,  to  allay  which,  as  much  as  poffible,  w^e 
chewed  the  leaves  of  the  Begonia  obliqua.  Two  of  the  negroes 
returned,  and  the  others  (liid  they  would  go  no  farther  w^ith 
me,  as  they  mull  perifh  for  want  of  water,  and  it  would  be 
impolfible  to  get  to  the  bottom  before  night,  and  they  muH:  all 

Vol.  LXXV.  E  die 


2  6  Mr.  x'^ndersqn's  Account  of  a 

die  in  the  woods.  The  propriety  of  their  reafoning  was  evi- 
dent to  me  ;  yet  I  thought  it  hard,  after  the  fatigues  of  three 
days  and  two  nights,  to  be  wltiiin  half  a  mile  of  the  top, 
and  not  be  able  to  get  up,  and  to  know  little  more  about  it  than  I 
did  at  the  bottom.  As  the  negroes  had  not  the  fame  motive 
for  going  up  as  I,  all  my  reafoning  was  to  them  ineffectual ;  I 
found  I  was  obliged  to  return  mvfelf,  as  I  could  not  perfift 
alone.  At  half  paft  twelve  we  began  to  defcend  the  fame  way 
we  came.  As  there  was  now  a  clear  path  all  the  way  to 
the  bottom,  we  got  down  to  Mr.  Gasco's  by  fun  fet.  After 
fitting  fome  time  here,  I  was  hardly  able  to  rife  again,  I  wasfo 
tired ;  and  m.y  feet  were  fo  fore  I  could  hardly  ftand  on  them,, 
for,  my  ihoes  being  torn  to  pieces,  I  came  down  the  whole  way 
bare-footed.  I  continued  my  journey,  however,  to  Mr.  Mat- 
Loune's,  where  I  arrived  between  fix  and  feven  at  night. 

March  4th,  being  the  day  I  had  fixed  to  finifli  my  excurfion, 
about  four  in  the  morning,  I  left  the  houfe  of  Mr.  FraseRj 
who  out  of  curiofity  agreed  to  accompany  me,  of  which  I  was 
very  glad,  as  he  was  a  fenfible  young  man  ;  and  with  the  affift- 
ance  of  two  negroes  we  purfued  our  journey.     We  found  very 
little  obftrudion  in  our  way  up,  until  we  got  to  the  place  where 
I  returned  ;  and  there,  for  about  a  quarter  of  a  mile,  wc  had 
conliderable  difficulty  to  clear  our  way  through  grafs  and  ferns. 
After  we  came  within  a  quarter  of  a  mile  from  the  top,  we 
found  ourfelves  in  another  climate  all  at  once,  the  air  very  cold, 
and  the  vegetable  productions  changed ;  here  was  nothing  but 
barrennefs  over  the  whole  fummit  of  the  mountain.     On  the 
confines  of  the  grafly  region  and  the  barren  I  found  fome  beau- 
tiful plants.    Mofs  grows  here  in  fuch  plenty,  that  I  frequently 
funk  up  to  my  knees  in  it.     This  is  the  only  place  in  the  Weft 
Indies  that  produced  any  mofs  that  I  have  feen.     About  nooa 
1  we 


f^okanic  Mountain  in  St.  Viucent*;5.  2^ 

\Ve  gaitied  the  top  of  the  peak  I  had  directed  my  conrfe  to  be- 
fore ;  when,  111  an  iiiAant,  we  were  lurprifcd  with  one  of  the 
grandeft  and  mod:  awful  fcenes  I  had  ever  beheki.  I  .vas  {truck, 
with  it  amazingly,  as  I  could  not  have  conceived  fiich  a  very, 
large  and  fo  finguiarly  formed  an  excavation.  It  is  iituated  on 
the  center   of    tlie   mountain,  and   where   the   various  ridces 

to         • 

unite.  Its  diameter  is  fomething  more  than  a  mile,  and  its  cir- 
cumference to  appearance  a  perfe6l  circle.  Its  depth  from  the 
»furrounding  margin  is  above  a  quarter  of  a  mile,  and  it  nar-. 
rows  a  little^  but  very  regularly,  to  the  bottom.  Its  fides  are 
very  Imooth,  and  for  the  moif  part  cov^ered  with  fliort  mofb^ 
except  towards  the  fouth,  where  there  are  a  number  of  fmali 
holes  and  rents.  This  is  the  only  place  where  it  is  poiTible  to 
go  down  to  the  bottom. :  it  is  exceedingly  dangerous,  owing  to 
the  numberlefs  fmall  chafms.  On  the  weft  fide  is  a  fe£llon  of 
red  rock  like  granite,  cut  very  fmoothj  and  of  the  fame  decli- 
vity with  the  other  parts.  All  the  reft  of  the  furrounding  f.des 
feems  to  be  compofed  of  fand,  that  looks  to  have  undergone 
the  adion  of  intenfe  fire.  It  has  a  cruft  quite  fmooth,  of 
about  an  inch  thick,  and  hard  almoft  as  rock  ;  after  breaking 
through  which,  you  find  nothing  but  loofe  fand.  In  the  center 
of  the  bottom  is  a  burning  mountain  of  about  a  mile  in  cir- 
cumference, of  a  conic  form,  but  quite  level.  On  the  fum^ 
mit,  out  of  the  center  of  the  top,  arifes  another  mount,  eight 
or  ten  feet  high,  a  perfed:  cone ;  from  its  apex  ifllies  a  column 
of  fmoke.  It  is  compofed  of  large  mafl'es  of  red  granite-like 
rock  of  various  fizes  and  fliapes,  which  appear  to  have  been 
fplit  into  their  prefent  magnitudes  by  fome  terrible  convulfion 
of  nature,  and  are  piled  up  very  regular.  From  moft  parts  of 
the  mountain  iffue  great  quantities  of  fmokej  efpecially  on  the 
north  fide,  which  appears  to  be  burning  from  top  to  bottom, 

E  2  -an4 


23  M>'.  A>)derson'3  Account  of  a 

nnd  the  heat  is  i"o  intcnfe,  that  it  is  impofiible  to  go  upon  It. 
Going  round  the  bafeis  very  dangerous,  as  large  mafles  of  rock 
are  conftantly  fplitting  with  the  heat,  and  tunibling  to  the  bot- 
tom. At  the  bottom,  ou  the  north-  lide,  is  a  very  kirge  rock 
fpiit  in  tu'o  ;  each  of  theie  halves,  which  are  ieparated  to  a- 
confiderable  dlftance  from  each  other,  is  rent  in  all  directions,  and- 
from  the  crevices  iiilie  efflorefcences  of  a  glofly  appearance,  which- 
tall-e  like  vitriol,  and  nHo  beautiful  cryflallizatioi-s  of  lulphur. 
On  ali'parts  of  the  mountain  are  great  quantities  of  fulphurin  all 
llal'-s;  alio  alum,  vitriol,  and  other  minerals.  From  the  external 
appearance  of  this  mountain,  1  imagine  it  has  only  begun  ta 
burn  lately,  as  on  feveral-  parts  of  it  I  faw  fmall  Ihrubs  ancl> 
grafs,  which  looked  as  if  they  liad  been  lately  fcorched  and'- 
burnt.  Tiiere  are  ievtral  holes  on  the  fouth,  from  which  iffues- 
fmoke,  feemingly  broken  out  lately,  as  the  bufhes  round  are  but' 
lately  burnt.  On  two  oppoiite  iides  of  the  burning  mountain,. 
eaR  and- wefl,  reaching  from  its  bale  to  that  of  the  lide  of  the 
crater,  are  two  lakes  of  water,  about  a  ftone's  throw  in  breadth  ; 
tP.cy  appear  to  be  deep  in  the  middle;  their  bottom  to  be  co- 
vered witlr  a  clay-like  lubilance.  The  water  leems  pleafant  to; 
the  tafle,  and  is  of  a  chalybeate  nature.  1  fuppofe  thefe  lakes- 
receive  great  increafe,  if  they  are  not  entirely  fupported,  by  tho 
rain  that  tumbles  down  the  fide  of  the  crater.  I  obferved  oii^ 
the  north  fide  of  the  bottom  traces  of  beds  of  rivers,  that  to 
appearance  run  great  quantities  of  water  at  times  to  both  thefe 
lakes.  By  the  llones  at  their  edges,  I  could  perceive  that  either, 
ablbrption  or  evaporation,  or  perhaps  both,  go  on  fr.ft.  The 
greater  part  of  the  bottom  of  the  crater,  except  the  mountain 
and  two  lakes,  is  very  level.  On  the  fouth  part  are  feveral 
Ihrubs  and  fmall  trees.  There  are  many  flones  in  it  that  feem 
to  be  impregnal'td  with  iDincrals :  1  law  feveral  pieces  of  pu- 
j  mice- 


volcanic  Mountain  in  St.  Vincent's.  29 

mice-ftone.  I  alfo  found  many  jftones  about  the  llze  of  a  man's 
fill,  rough,  on  one  fide  blue,  which  appearance,  I  imagine, 
they  have  got  from  heat,  and  being  in  contadi  witli  fome 
ininerah  Thefe  ftones  are  fcattered  over  the  whole  mountain, 
one  or  two  of  which  I  have  ferit  you,  with  fome  others. 

After  I  had  got  up  from  the  bottom  of  the  crater,  I  could  not 
help  viewing  it  with  admiration,  from  its  wonderful  {Irudure 
and  regularity.  Here  1  found  an  excavation  cut  through  the 
mountain  and  rocks  to  an  amazing  depth,  and  with  as  mucli 
regularity  and  proportion  of  its  conflituent  parts,  as  if  it  had 
been  planned  by  the  hand  of  the  moft  Ikilful  mathematician.  I 
wlfhed  much  to  remain  on  the  mountain  all  night,  to  examine 
its  feveral  ridges  with  more  attention  next  day ;  but  1  could  not- 
prevall  on  my  companion  to  f!:ay,  and  therefore  thought  it 
advifable  to  accompany  him. 

I  obferved  the  motion  of  the  clouds  on  this  m.ountain  to  be 
very  fingular.  Althongh  there  are  feveral  parts  on  it  higher 
than  the  mouth  of  the  crater,  yet  I  faw  their  attra6lIon  was 
always  to  it.  After  entering  on  its  eafl:  or  windward  fide,  they 
funk  a  confiderable  way  into  it ;  then,  n:iounting  the  oppofite 
fide,  and  whiiling  round  the  north- weft  fide,  they  ran  along  a. 
ridge,  \vhich  tended  nearly  north-eaft,  and  afterw-ards  funk 
into  a  deep  ravin,  which  divided  this  ridge  from  another  on  the- 
north-weft  corner  of  the  mountain,  and  the  highefton  it,  lying 
in  a  diredllon  nearly  fbuth  and  north.  They  keep  thecourfe  of 
this  ridoe  to  the  fouth  end,  and. then  whirl  oiT  weft  in  their, 
natural  courle. 

I  took  my  departure  from  the  mountain  with  great  reluctance,- 
Although  I  encountered  many  difficulties  to  get  up,  yet  it 
amply  rewarded  me  for  all  my  toil ;  but  I  had  not  time  to 
examine  it  with- that  attention  I  wifticd.     When  I  got  on  the: 

peak. 


j} 6  Mr .  Anderson*s  Account  of  a 

peak  from  which  I  hud  my  C\v^  vkw  of  k,  and  ffotn'  which  ! 
could  Ice  Its  diffl?reut  parts,  I  could  not  help  reviewing  it 
feveral  times.  After  Imprinting  its  fl:ru(5lure  on  my  mind,  I 
rook  my  final  adieu  of  it,  and  returned  down,  and  got  to  Mr.. 
Fr  ASER*s  houfe  about  feven  at  night,  much  fatigued. 

I  am  forry  I  had  no  inftruments,  to  take  the  ftate  of  the  air-^ 
'nor  the  exacl;  dimenflons  of  the  different  parts  of  the  moun-* 
tain;  hut,  I  believe^  on  raeafurement,  they  w4U be  more  than: 
i  have  mentioned. 

From  the  fituation  of  thefe  iHands  to  one  another,  and  to  the 
continent  of  South  Araeiica,  I  imagine  there  are  fub-marine 
communications  between  the  burning  mountains  or  vokanoeg 
in  each  of  them,  and  from  them  to  the  volcanoes  on  the  high 
inoimtalns  of  America,     The  iflands,  which   are  fituated  next 
the  continents  feem  to  tend  in  the  diredion  of  thofe  moun- 
tains ;  and  I  have  obferved,  that  the  crater  in  this  ifland  lies 
nearly  in  a  line  with  Soufriere  in  St.  Lucia  and  Morne  Pelee  in 
^Martinique,  and  I  dare  fay  from  Morne  Pelee  to  a  place  of  the 
fame  kind  in  Donrfinique,  and  from  it  to  the  others ;  as  it  is  cer- 
tain there  is  fomething  of  this  kind  in  each   of  thefe  iflands, 
Barbadoes  and  Tobago  excepted,  which  are  quite  out  of  the 
range  of  the  refl. 

There  is  no  doubt  but  eruptions  or  different  changes  in  fome 
of  them,  although  at  a  great  diftance,  may  be  communicated 
to  and  affe61:  the  others  in  various  manners.  It  is  obferved  by 
the  inhabitants  round  thefe  burning  mountains,  that  fhocks  of 
earthquakes  are  frequent  near  them,  and  more  fenfibly  felt 
than  in  other  parts  of  the  ifland,  and  the  fhocks  always  go  in 
the  dire^Vion  of  them. 

I  cannot  omit  mentioning  this  great  affiftance  I  received  in 
the  above  excurfion  from  Dr.  Young,  Mr.  Maloune,  and  Mr. 

Fraser; 


Volcanic  Mountain  in  St.  Vincent's.  ^i' 

Fraser  ;  for,  without  the  aid  of  their  negroes,  I  could  not 
have  poflibly  gone  through  with  it. 


References  to  the  figure,  tab.  IL 

A  K  The  fummit  that  overlooks  the  crater,  from  which,  the. 

drawing  is  taken. 
AAAA.  The  circumference  of  the  crater. 
BBBB.  The  circumference  of  the  bottom. 

C.  The  burning  mountain. 

D.  The  fmall  one  on  its  fummit. 
EE.  The  two  lakes  of  water. 

F.  The  fe£tion  of  the  rock  on  the  weflfide  of  the  crater* 

G.  The  large  ravin. 
HHHH.  Ravins  of  great  depth; 

I,  Efflorefcence  on  the  north  end  of  the  rock,  which  at  a. 
diftance  looks  like  alum  or  nitre. 

1.2.3.4.5.6.  The  different  ridges  on  the  fummit  of  the  moun- 
tain, as  they  join  the  crater. 

7.  Woods  deftroyed  by  the  hurricane. 

8.8.  The  clouds  going  to  the  fouthward  of  the  weft  ridgc^. 
after  pafiing  north  on  the  weft  fide  of  the  crater. 

9.9.9.  Where  I  defcended  into  the  bottom  of  the  crater. 

L  and  10.  The  fummit  and  bafe  of  the  ridge  on  which  J> 
afcended  the  mountain. 


[    3^    3 


IV.  A  Supplement  to  the  Third  Pari  of  the  Paper  en  the  Sum- 

matlon  of  hifinite  Series,  in  the  PJiilofophical   Tranfadions 

for    the    Year    1782.       By   the    Rev.    S.  Vince,    M  ^. ; 

communicated    by     Nevil   MalkeJvne,    D.  D.  F.  R.  S.   and 

Aftronomer  Royal, 


Read  November  25,  1784. 

^"^HE  reafoning  in  the  third  part  of  my  paper  on  the  Sum- 
^  mation  of  infinite  Series  having  been  midinderftood,  I 
have  thought  it  proper  to  offer  to  the  Royal  Society  the  follow- 
ing explanation.  When  I  propofed,  for  example,  to  fum  the 
feries  I  -  *  +  5  -^  hcz,  fine  fine^  I  wanted  to  find  fome  quantity 
which,  by  its  expanfion,  would  produce  that  feries,  and  that 
quantity  I  called  its  fum  ;  not  (as  I  conceived  mufl  have  been 
evident  to  every  one)  in  the  common  acceptation  of  that  word, 
that  the  more  terms  we  take,  the  more  nearly  we  fhould 
approach  to  that  quantity,  and  at  laft  arrive  nearer  to  it  than 
by  any  affignable  difference,  for  there  manifeflly  can  be  no  fuch 
quantity ;  but  as  being  a  quantity  from  which  the  feries  mufl 
have  been  deduced  by  expanfion,  which  quantity  I  found  to  be 
—  i  +  H.  L.  2.  If  therefore  in  the  folution  of  any  problem, 
the  conclufion,  whofe  value  1  want,  is  exprefled  by  the  above 
feries,  and  which  arofe  from  the  necefhty  of  expanding  fome 
quantity  in  the  preceding  part  of  the  operation,  furely  no  one 
can  deny  but  that  I  may  fubflitute  for  it  -  |  +  H.  L.  2.  For 
whatever  quantity  it  was,  which  by  its  expanfion  produced  at 

iirfl 


I'M,:,  Tmm  V,,/  L  X\Y.  TaU  1/^,31. 


Mr.  Vince's  Supplement^  &c.  3^ 

firfl  a  ferles,  the  fame  redu«5lIon  which,  from  that  feiies,  pro- 
duced the  feries  i-*-+|— &c.  mull:  alfo  have  produced 
—  I  +  H.  L.  2.  from  the  quantity  which  was  expanded.  This 
value  of  the  feries  I  obtained  in  the  following  manner.  I  fup- 
pofed  the  feries  I  —  4  +  ?  ""  ^^'  ^^  ^^  divided  into  two  parts  ; 
the  firft  part  to  contain  all  the  terms  till  wc  come  to  thofc 
where  the  numerators  and  denominators  become  both  infinitely 
great,  in  which  cafe  every  term  afterwards  may  be  fuppofed  to 
be  equal  to  unity  :  the  fecond  part,  therefore,  would  neceflarily 
be  (fuppofing  the  firll:  part  to  terminate  at  an  even  number  of 
terms)  i  -  i  +  i  -  i  ■{■Scz.fnefme,     The  firft  part,  hy  coUed- 

inp;   two    terms  into  one,  becomes ^- &c. 

^  2.34-56.7 

which  feries,  as  it  is  continued  till  the  terms  become  infinitely 
fmall,  is  equal  to  -  i  +  H.  L.  2.  The  fecond  part  i  -  i  +  i  — 
&c.has  not,  taken  abftra6tedly  of  its  origin,  any  determinate  value 
(as  will  be  afterwards  obferved),  butconfidered  as  part  of  the  ori- 
ginal feries  it  has,  for  that  feries  muft  have  been  deduced  from  the 

expanfion  of  the  binomial  i  +x\     ,  or  — — ;  and  hence,  when 

J?=  I,   I  -  I  +  I  -&c.  can  in  this  cafe  have  come  only  from 

,  which,  therefore,    mull:   be   fubftituted   for  it ;    confe- 

quently  the  two  parts  together  give  —  f  -}-  H.  L.  2. 

Having  thus  explained  the  nature  of  the  feries  which  I  pro- 
pofed  to  fum,  and  the  principle  upon  which  the  corre6lioit 
depends,  I  muft  beg  leave  to  acknowledge  my  obligations  to 
my  very  worthy  and  ingenious  friend  George  ATwooD,Efq. 
F.R.S.  who  firft  obferved  that  the  feries  i  —  i  +  i  —  i  +  &:c.  has 
no  determinate  value  in  the  abftradb,  as  it  may  be  produced  by 

— 1 — ; — r-; — whatever  be  the  number  of  units  ia  the  denomi- 

J  +  I  +  I  +&C. 

Vol.  LXXV.  F  nator; 


34  ^''''  Vince's  Supplement  on  the 

jiator  *  ;  and  it  may  alfo  be  added,  that  the  fame  feries  arlfes- 

from  —— ---    ,"^  .  '     ,  provided  the  number  of  units  be  g-reater  in 

I  -f-  I  -|-  I  -J-  I  -j-OtC.      '■  o 

the  denominator  than  in  the  numerator.  The  ccrre6lion  will 
therefore  be  different  in  different  circumftances,  and  will  depend 
on  the  nature  of  the  quantity  which  was  at  firft  expanded.  In 
the  third  part  of  my  paper,  I  appHed  the  correction  to  thofe  cafes 
where  the  original  feries  arofe  from  the  expaniion  of  a  binomial, 
where  the  corre6lion  is  in  general  as  I  tliere  gave  it ;  but  as  I 
did  not  apply  my  method  to  any  other  feries,  1  confeis  that  it 
did  not  appear  to  me,  that  the  correction  would  then  be  dif- 
ferent, which  it  neceffarily  would  had  [  extended  my  reafon- 
ing  to  other  cafes.  1  fliall  therefore  add  one  example  to  (hew 
the  method  of  corredlion  in  other  inftances,  where  the  value 
of  the  correction  will  be  found  to  be  different,  according  as  we 
beoin  to  collect  at  the  firlf  or  fecond  term-.  Let  the  leiies  be 
.*  _  1 4.  5  _  6  _[_  8^  _  ^c.  fine  fine^    which    camie  originally  from 

___J ^ ;  DOW  if  we  bepin  to  colled  at  the  firfl:  term,  the  feries 

becomes  ~—  H — ^ — V  &c.  and  for  the  fame  reafon  as  before,  the- 
1.2     4-5 

correaion,  to  be  added,  is  ]. ;  but  — —  +  —  -  -1-  &c.  ~  \-  of  a 
»  1.24.5 

circular  arc  (A)  of  30"  to  the  radius  — -  ;  hence  the  fum  re- 
quired =±A+ 4-.  ■  If  we  begin  to  colled  at  the  fecond  term  the 

feries  becomes  2 -" -^ &c. ;  and   the  corredion   to  be 

2.4     5.7 

fubtracled  is  4 ;  for  the  fecond  part  of  the  original  feries  is  now 
_  I  4-  I  _  I  ^_  I  _&c.    which  was   produced  by  -  ,       -;    but 

*  I  have  been  fince  informed  by  Mr,  Wales,   F.  R.  S,  that  a  pupil  of  his,  Mr, 
OND,  made  the  fame  obfervation, 
J 


Summation  of  Injinhe  Series, 


35 


2 ?_ . ^- —  &c.  =  I  -f  *  A  ;  therefore  the  fum  required  — 

2.45-7  ' 

-V  +  ±  A  as  before.  In  the  fame  manner  we  may  apply  the  cor^ 
je6tion  in  all  other  cafes.  Although,  therefore,  the  feries 
I  -  I  +  I  —  I  4-  &c.  or  — i  +  i-i  +  i-  &c.  have  no  determi- 
nate value  in  the  abftrad,  yet  the  ^ven  feries  will  fix  its  value 
by  pointing  out  the  quantity  from  which  the  feries  muft  have 
been  originally  produced. 


F  2 


[     36    J 


V.  Defcription  of  a    Plant  yielding  Afa    foetlda.     In  a  Letter 
jrom  John   Hope,  M,  D.  F.  R,  S.  to  Sir  Jofeph  Banks, 
Bart,  P.  R.  S. 


Read  December  9,  1784. 

TO    SIR    JOSEPH    BANKS,    BART.  J.R.S. 
S  I  R,  Edinburgh,  Auguft  18,  Ij84» 

I  BEG  you  will  do  me  the  honour  of  prefenting  the  inclofed 
account  of  the  Afa  foetida,  and  the  botanical  defcription  of 
the  plant,  with  the  drawings,  to  the  Royal  Society. 

1  have  the  honour  of  being,  with  much  refpcd  and  efteem,  &c^ 

JOHN    HOPE. 


A  S  A    F  OE  T  I  D  A. 

PLAKTAumbellifera,  tripedalis,  ere6la,  ramofa,  glauca^ 
flore  luteo.- 
Radix  perennis.. 

Folia  radicalia  fex,  procumbentia,  trilobo-ovata,  multoties 
pinnatim  divifa ;  foliolis  incifis,  fubacutis,  fub- 
decurrentibus  ;  petlolo  communi  fuperne  piano,  linea 
elevata  longitudinaliter  per  mediunx  decuprente. 

a  Cauh's, 


Dr.  Hope's  Defcrtpiion,  kc.  y^ 

Caulis  bipedalls,  eredtus,  teretiufculus,  annuus,  leviter  ftria- 
tus,  glaber,  nudus  praeter  unam  circa  medium  fo- 
liorum  imperfedorum  conjugationem  ;  petlolo  mem- 
bran  aceo,  concavo. 
Rami  nudi,  patuli ;  quorum  tres  inferi,  alterni,  fuflinentur 
fuiguli  folii  imperfedi  petiolo  membranaceo  con- 
cavo. 
Quatuor  intermedii  vertlcillati  funt.     Supremi  ex  aplce 

caulis  o6lo,   quorum  interni  ere6ll. 
Omnes  hi  rami  fummitate  fuftlnent   umbellam  com- 
pofitam  feffilem  terminalem,  et  prasterea  3 — 6  ramulos 
externe  politos,  umbellas  compofitas  ferentes. 
Hoc  modo,  rami  inferiores  luflinent  5,  raro  6  ramulos ; 
intermedii  3  vel  4;   fuperiores  i  et  2. 
Cal.  TJmbella  tmiverfalis  radiis  20  —  30  conflat. 

• — partialis  flofculis  fubfeffilibus  10 — 20. 

Vmhella  compojita  feffilis  convexo-plana. 

. ■  pedunculata  hsemifpherica. 

Involucrum  univerfale  nullum.. 

— partiale  nullum. 

Perianthium  proprium  vix  notablle. 
CoR.  univerfalis  uniformls. 

Flofculi  umbellae  feffilis  fertiles. 

.  pedunculatae  plerumque  abortiunt. 

propria  petalis  q^ulnque  aequalibus,  planis,  ovatis  :  primo 
patulis,  dein  reflexis,  apice  afcendente. 
St  AM.  Ftlamenia  5,  fubulata,  corolla  longiora,  incurvata.     An^ 

thera  fubrotundae. 
PiST.  Germen  turbinatum,  inferum* 
Sty  It  duo,  reflexi. 
Stigmata  apice  incraflata* 

Fer. 


sS  Dr,  Hope's  De/cnf>f!on  of  a 

Per.  nullum  :  fruclus  oblongus,  piano- comprefTus,  utrlnque  3 

lineis  elevatis  notatus  eft. 
Sem.   duo,    oblonga,  magna,  utrinque  plana,  3  lineis  elevatis 

notata. 
Planta  odorem  alliaceum  diffundit.    Folia,  rami,  pedun- 

culi,  radix,  truncus,  fe£li  fuccum  fundunt  ladeum, 

fapore  et  odore  Ala,*  foetid^. 


THOUGH  Afa  foetida  has  been  ufed  in  medicine  for  many- 
ages,  having  been  introduced  by  the  Arabian  phy(icians  near  a 
thoufand  years  ago ;  yet  there  was  no  fatisfaftory  account  of 
the  plant  which  yielded  it,  tillKiEMPFER  publifhed  his  Amoeni- 
tates  Exoticae  about  feventy  years  ago. 

KiEMPFER,  towards  the  end  of  the  lafl  century,  travelled 
over  a  great  part  of  Afia,  and  was  in  Perfia,  and  upon  the  fpot 
where  the  Afa  foetida  is  collected.  He  gives  a  full  account  of 
the  manner  of  collecting  it.  He  defcribes  the  plant  ;  and  alfd 
gives  a  figure  of  it,  differing  in  many  refpe£ts  from  thofe  which 
I  now  prefent  to  the  Society  *. 

Six  years  ago,  I  received  from  Dr. Guthrie,  of  St.  Peterfburg, 
F.  R.  S.  two  roots  of  the  Afa  foetida,  with  the  following  card 
from  Dr.  Pallas,  addreffed  to  Dr.  Guthrie  : 

"  Dr.  Pallas's  compliments  to  Dr.  Guthrie  ;  he  fends 
"  him  two  roots  of  the  Ferula  Afa  foetida,  a  plant  which  he 

*  Probably  K^mpfer's  Afa  foetida  Plant  is  a  different  fpecies  from  that 
defcribcd  hyDr.  Hope  in  this  paper.  K^mpfer  was  himfelf  upon  the  mountains 
where  the  drug  is  collefted,  and  his  fidelity  in  defcribing,  as  well  as  delineating,  has 
not  hitherto  been  impeached.  Sanguis  Draconis,  and  fome  other  gums,  are 
indifferently  the  produce  of  various  fpecies  of  plants ;  and  why  may  not  Afa 
foetida  be  fimiU.rly  circumllanced  ?         Jos.  Banks. 

"  thinks 


l-hUrj  Trnnj .  K,l  LXXV  T«bJII.;>.jit. 


rcetiaa  be  limiU.rly  circumflanced  ?         Jos.  Banks. 


P Lint  yielding  h(A  fdticla.  ^^ 

*'  thinks  never  was  cultivated  in  any  European  garcien,  and 
'*  which  nobody  has  been  fo  fortunate  as  to  raile  from  feed  but 
*'  Iiimfeif,  thouph  the  feeds  fent  to  the  Academy  from  the 
**  mountains  of  Ghilan  in  Perfia  had  been  diftributed  among 
•*  feveral  curious  perfons." 

Both  thefe  roots  were  planted  in  the  open  ground,  in  the 
Botanic  Garden  at  Edinburgh  ;  one  died  ;  the  other  after  fome 
time  did  well,  and  laft  lummer  flowered  and  produced  feed.  I 
had  an  accurate  drawing  of  the  plant  made  by  Mr.  Fife,  wliich 
I  now  have  the  pleafure  of  laying  before  the  Society.  It  ex- 
prefl'es  very  well  the  general  habit  of  the  plant,  which  was  of 
a  pale  fea- green  colour,  and  grew  to  the  height  of  three 
feet.  The  ftem  is  deciduous,  but  the  root  is  perennial. 
Every  part  of  the  plant,  when  wounded,  poured  out  a  rich 
milky  juice,  refembling  in  fmell  and  tafte  Afa  foetida ;  and  fit 
times  a  fmell  refembling  garlick,  fuch  as  a  faint  impregnation 
of  Afa  foetida  yields,  was  perceivable  at  the  diftance  of  feveral 
feet. 

In  Perlia,  at  the  proper  feafon,  the  root  is  cut  over  once  and 
again  ;  from  the  inciiions  there  flows  a  thick  juice  like  cream, 
wliich,  thickened,  is  the  Afa  foetida. 

I  have  only  further  to  obferve,  that  as  the  plant  grows  in 
the  open  air,  without  prote(£l:ion,  and  even  in  an  unfivourable 
leafon  produced  a  good  deal  of  feed,  and  as  the  juice  feems  to 
be  of  the  fame  nature  with  the  officinal  Afa  foetida,  there  is 
fome  reafon  to  hope,  that  it  may  become  an  article  of  cultiva- 
tion in  this  country  of  no  inconfiderable  importance. 

Edinburgh,  Jan.  1783. 


\:0 


[     40     1 


VI.  Catalogue  of  Double  Stars, 
By  William  Herfchel,  Efq,  F,  R,  S. 

Read  December  9,  1784. 

INTRODUCTORY     REMARKS. 

THE  great  ufe  of  Double  Stars  having  been  already  pointed 
out  in  a  former  paper,  on  the  Parallax  of  the  Fixed  Stars, 
and  in  a  latter  one,  on  the  Motion  of  the  Solar  Syftem,  I  have 
now  drawn  up  a  fecond  coUedion  of  434  more,  which  I  have 
found  out  fmce  the  firfl  was  delivered. 

The  happy  opportunity  of  giving  all  my  time  to  the  purfuit 
of  aftronomy,  which  it  has  pleafed  the  Royal  Patron  of  this 
Society  to  furniih  me  with,  has  put  it  in  my  power  to  make 
the  prefent  colledion  much  more  perfedl  than  the  former; 
almofl  every  double  ftar  in  it  having  the  diftance  and  pofition 
of  its  two  flats  meafured  by  proper  micrometers ;  and  the 
obfervations  have  been  much  oftener  repeated. 

The  method  of  claffing  them  is  in  every  refped  the  fame  as 
that  which  has  been  ufed  in  the  firfl:  collection ;  for  which  rea- 
fon  I  refer  to  the  introductory  remarks  that  have  been  given 
with  that  coUedion  *  for  an  explanation  of  feveral  particulars 
necefTary  to  be  previoufly  known.  The  numbers  of  the  flars 
are  here  alfo  continued,  fo  that  the  firfl  clafs  ending  there  at 

♦  See  PhilofophicalTranfaaions,  vol.  LXXII.  p.  112. 

24 


Air,  Herschel's  Catalogue  of  Double  Stars,  41 

24  begins  here  at  25,  and  the  fame   is  done  with  the  other 
clafles. 

Moil:  of  the  double  ftars  in  my  firfl:  collection  are  among  the 
number  of  thofe  ftars  which  have  their  places  determined  in 
Mr.  Flamsteed's  extenfive  catalogue  ;  but  of  this  colledicn 
many  are  not  contained  in  that  author's  work,  I  have  therefore 
adopted  a  method  of  pointing  them  out,  which  it  will  be  prooer 
to  defcribe. 

The  finder  of  my  reflector  is  limited,  by  a  proper  diaphragm, 
to  a  natural  field  of  two  degrees  of  a  great  circle  in  diameter. 
The  interle<51:ion  of  the  crofs  wires,  in  the  center  of  it,  points^ 
out  one  degree ;  and  by  the  eye  this  degree,  or  the  diilance. 
from  the  center  to  the  circumference,  may  be  divided  into  I, 
I,  I,  -1^  ^iid  f.  Thus  we  are  furnifhed  with  a  meafure  which,. 
though  coarfe,  is  however  fufficiently  accurate  for  the  purpofe,- 
here  intended ;  and  which,  if  more  than  two  degrees  are 
wanted,  may  be  repeated  at  pleafure. 

In  fuch  meafures  as  thefe  I  have  given  the  diftance  of  a  dou-. 
ble  ftar,  whofe  place  I  wanted  to  point  out,  from  the  neareft 
flar  in  Flamsteed's  Catalogue.  And  fince,  befides  the 
diftance,  it  is  alfo  required  to  have  its  pofition  with  regard  to 
the  ftarthus  referred  to,  I  have  ufed  the  neighbouring  ilars  for 
the  purpofe  of  pointing  it  out. 

The  ufefulnefs  of  this  method  is  fo  extenfive,  that  I  fhall  be 
a  little  more  particular  in  defcribing  its  application.  When  a 
ftar  is  thus  pointed  out,  as  for  inftance  the  32d  in  the  firll:  clafs, 
where  it  is  faid,  '*  About  |  degree  f.  preceding  the  44th  Lyncis, 
*'  in  a  line  parallel  to  Q  Urfas  majoris  and  the  39th  Lyncis  ;"  we 
are  to  apply  one  eye  to  the  finder,  and  placing  the  44th  Lyncij 
into. the  center  of  the  field,  we  are  to  look  at;^.Urfae  majoris 
and  the  39th  Lyncis  in  the  heavens  with  the  other  eye  by  the 

Vol.  LXXV.  G  Uz 


4i  Mr.  Hersctjei/s  Catalcguc 

lide  of  the  hndt-r.  The  naked  eye  then  wiH  immediately  direct 
us,  by  means  of  the  two  ftars  juft  mentioned,  towards  the 
place  where,  in  the  finder,  the  armed  eye  will  perceive  the 
double  flar  in  queftion  about  |  degree  from  the  44th  Lyncis.  I 
need  hardly  obferve,  that  we  muft  recollect  the  inverlion  of  the 
finder,  as  thofe  who  are  in  the  habit  of  uling  telefcopes  with 
high  powers,  always  furniihed  with  inverting  finders,  will  of 
courfe  look  for  the  fmall  flar  in  the  upper  part  of  the  field,  as 
in  fig.  I. 

At  the  45th  flar,  in  the  firfl  clafs,  the  defcription  fays, 
"  About  1 1  degree  f.  preceding  ^,  towards  1  Aurigae.'*  This 
double  flar  will  accordingly  be  found  by  placing  ^  Aurigse  firft 
into  the  center  of  the  finder;  then,  drawing  the  telefcope 
towards  /,  which  the  naked  eye  points  out,  the  ftar  we  look  for 
will  begin  to  appear  in  the  circumference  as  foon  as  ^  is  about 
I  degree  removed  from  the  center,  as  in  fig.  2. 

It  will  fometimes  happen,  that  other  flars  are  very  near 
thofe  which  are  thus  pointed  out,  that  might  be  miftakeii  for 
them.  In  fuch  cafes  an  additional  precaution  has  been  ufed  by 
mentioning  fome  circumftance  either  of  magnitude  orfituation, 
to  diilinguifh  the  intended  flar  from  the  reft.  After  all,  if  any 
obferver  fhould  be  ftlU  at  a  lofs  to  find  thefe  ftars  without  having 
their  right  afcenfion  and  declination,  he  may  furnifh  himfelf 
with  them  by  means  of  Flamsteed's  Atlas  Cceleftis ;  for  my 
defcription  will  be  fafficiently  exadl  for  him  to  make  a  point  in 
the  maps  to  denote  the  ftar's  place;  then,  by  means  of  the  gra- 
duated margin,  he  will  have  its  J^  and  declination  to  the  time 
of  the  Atlas,  which  he  may  reduce  to  any  other  period  by  the 
ufual  computations. 

Before  I  quit  this  fubje£l  I  muft  remark,  that  it  will  be  found 
on  trial,  that  this  method  of  pointing  out  a  double  ftar  is  not 

only 


of  Double  Stars,  43 

only  equal,  but  Indeed  fuperlor,  to  having  its  liglit  afcenfion 
and  declination  given  :  for,  fince  it  is  to  be  viewed  with  very 
high  powers,  not  fuch  as  fixed  inftruments  are  generally  fur- 
niflied  with,  the  given  right  afceniion  and  declination  would  be 
of  no  fervice.  We  might,  indeed,  find  the  ilar  by  a  fixed  or 
equatorial  inftrument ;  and,  taking  notice  of  its  fituation  with 
regard  to  other  neighbouring  ftars,  find,  and  view  it  after- 
wards, by  a  more  powerful  telefcope ;  but  this  will  nearly 
amount  to  the  very  fame  way  which  here  is  purfued,  with  more 
deliberate  accuracy  than  we  are  apt  to  ufe,  while  we  are  em- 
ployed in  feeking  out  an  obje£l  to  look  at. 

It  will  be  required,  that  the  obferver  (hould  be  furnifhed 
with  Flamsteed's  Atlas  Coeleftis,  which  muft  have  the  jflars 
marked  from  the  author's  catalogue,  by  a  number  eafily  added 
to  every  ftar  with  pen  and  ink,  as  I  have  done  to  mine.  The 
catalogue  fhould  alfo  be  numbered  by  an  additional  column, 
after  that  which  contains  the  magnitudes.  I  hope  in  fome 
future  editions  of  the  Atlas  to  fee  this  method  adopted  in  print, 
as  the  advantage  of  it  is  very  confiderable,  both  in  referring  to 
the  catalogue  for  the  place  of  a  ftar  laid  down  in  the  Atlas,  and 
in  finding  a  flar  in  the  latter  whofe  place  is  given  in  the 
former. 

I  would  recommend  a  precaution  to  thofe  who  wifh  to  exa- 
mine the  clofeft  of  my  double  ftars.  It  relates  to  the  adjufl 
ment  of  the  focus.  Suppofing  the  telefcope  and  the  obferver 
long  enough  out  in  the  open  air  to  have  acquired  a  fettled  tem- 
perature, and  the  night  fufficiently  clear  for  the  purpofe ;  let 
the  focus  of  the  inflrument  be  re-adjufted  with  the  utmoft 
delicacy  upon  a  ftar  known  to  be  fingle,  of  nearly  the 
fame  altitude,  magnitude,  and  colour,  as  the  ftar  which  is  ^o 
be  examined,  or  upon  one  flar  above  and  another  below  the 

G  2  fame. 


44  ^^^'  Hep SCH el's  Catalogue 

lame.  Let  die  phasnomcna  of  the  adjufting  ftar  be  welf 
attended  to;  as,  whether  it  be  perfedliy  round  and  well  de- 
fined, or  affeded  with  little  appendages  that  frequently  keep 
playing  about  the  image  of  the  ftar,  undergoing  fmall  alte«'a- 
tions  while  it  paiTes  through  the  field,  at  other  times  remain- 
ing fixed  to  it  during  the  whole  pafTage,  Such  deceptions  may 
be  detefted  by  turning  or  unfcrewing  the  obje6t-gLifs  or  fpecu- 
ium  a  little  in  its  cell,  when  thofe  appendages  will  be  obferved 
to  revolve  the  fame  w^ay.  Being  thus  acquainted  with  the 
jmperfeilions  as  well  as  perfedlions  of  the  inftrument,  and 
going  immediately  from  the  adjufting  ftar,  which  for  that 
reafon  alio  fhould  be  as.  near  as  may  be,,  to-  the  double  flar  which, 
is  to  be  examined,  we  may  hope  to  be  fuccefsful.  The  aftrc- 
nomical  Mr.  Aubert,  who  did  me  the  honour  to  follow  this 
method  with  y  Leonis,  which  he  did  not  find  to  be  double 
when  the  telefcope  was  adjufted  by  y  itfelf,  foon  perceived  the 
fmall  ftar  after  he  had  adjufted  it  upon  Regulus.  The  inilru^ 
ment,  being  one  of  Mr.  Doi.lond's  bcil  3I  feet  achroma- 
tics,  fliewed  Mr^  Aubert  the  two  flars  of  y  Leonis  in  very 
clofe  conjundion,  or  rather  one  partly  hid  behind  the  other- 
On  comparing  thefe  appearances  with  my  obfervations  of  that 
double  ftar,  w-e  muft  not  be  furprifed  to  find  that  I  place  them, 
at  a  vifible  diftance  from  each  other  :  for  the  Newtonian  ref' 
fledors,  on  the  plan  of  ray  7-feet  one,,  as  I  have  found,  will 
give  a  much  fmaller  image  of  the  ftars  than  the  3^  feet  achro- 
matic refradors  ;  wherefore  the  two  ftars,  which  in  refradorsr 
as  it  were  run  into  each  other,  will  in  the  refledor  remaia 
feparate.  For  this  reafon  alfo,  thofe  who  only  ufe  fuch  re- 
fradors  muft  not  be  difappointed  if  they  cannot  perceive  the. 
26th,  30,  31,  36,  41,  44,  46,  47,  60,  75j  82,  86,  and  87th 
ftars  of  my  firft  clafs  to  be  double, 

A 


oj  DvuhU  Stars.  45 

•  AW  the  obierviitions  in  the  following  catalogue  on  the  rela- 
tive magnitude,  colour,  and  pofition  of  the  flars,  are  to  be 
underftood  as  having  been  made  with  a  power  of  460,  unlefs 
thcv  are  marked  otherwife.  This  will  account  fo.r  t!ie  dif- 
fereiice  which  obfervers  may  find  in.  the  relative  magnitude  ;  for 
fhould  they  ufe  only  a  power  of  about  200,  many  of  the 
fmali  ftars  that  are  lliid  to  be  very  unequal  and  extremely  une- 
qual, muft  appear  to  them  perhaps  a  degree  lower  in  the  fcale, 
and  become  extremely  and  exccliively  unequal  :  and  this  will 
happen,  though  the  quantity  of  light  fhould  be  the  very  fame 
which  the  refledtor  has  that  ferved  me  to  fettle  thefe  particulars. 
I  need  not  fay,  that  on  other  accounts,  fuch  as  a  real  difference 
in  the  light  of  the  telefcope,  the  pre  fence  of  the  moon,  twi- 
lights, aurorse  boreales,  or  other  eaufes,  many  of  the  fmall 
flars  may  be  found  to  be  of  a  different  comparative  luflre  from 
what  is  afligned  to  them  In  the  catalogue.  The  fmall  ftar  near 
Rigel,  for  Inftance,  appears  of  a  beautiful  pale  red  colour,  full,, 
round,  and  well  defined,  with  my  20-feet  reflector  j  the  lo-feet 
inflrument  fhews  it  alfo  very  well  in  fine  evenings  ;.  the  ^-feet 
requires  more  attention,  nor  is  the  Imall  flar  defined,  but  of  a 
duiky  pale  red  colour.  A  good  3I  feet  achromatic,  of  a  large 
aperture,  when  Rigel  is  on  the  meridian,,  may,  perhaps,  alfo 
f-iew  the  fmall  flar,  although  1  have  not  been  able  to  fee  it 
with  a  very  good  inftrument  of  that  fort,  which  fhews  the 
fmall  flar  that  accompanies  the  pole-flar  ;  but  the  evening  was 
not  very  favourable. 

The  meafures  of  the  diflances  were  all  taken  with  a  parallel 
filk- worm's- thread  micrometer,  and  a  power  of  227  only.. 
They  are  not,  as  in  the  former  catalogue,  with  the  diameters 
included^  hut  fi"om  the  center  of  one  f}:ar  to  the  center  of  the 

other.. 


^5  Mr.  Hersciiel's  Catalogue 

oth^r.  I  iiare  adopted  thefe  meafures  on  finding  that  I  could 
procure  threads  fine  enough  to  lubtend  only  an  angle  of  about 
i^'  1^1'' -i  and  that  by  this  means  there  was  no  longer  any 
great  difficulty  of  judging  when  the  flars  were  centrally  co- 
vered by  the  threads.  However,  I  do  net  know  whether  thele 
meafures,  with  ftars  at  a  confiderable  diftance,  may  not  be 
liable  to  an  additional  error  of  perhaps  one  fecond,  owing  to 
the  remaining  uncertainty  in  judging  of  their  cxad:  central 
pofition  while  the  meafure  is  taking. 

The  pofitions  have  all  been  meafured  (unlefs  marked  other- 
wife)  with  a  power  of  460,  adapted  to  an  excellent  microme- 
ter, executed  by  Mefl'.  Nairne  and  Blunt,  according  to 
the  model  given  in  the  PhilofophicalTranfa6tions,  vol.  LXXI. 
pnge  500-.  fig.  IV.  ;  but  with  a  great  and  neceflary  improve- 
ment of  'making  the  wheel  d^  d^  of  that  figure  perform  its 
whole  revolution  ;  bv  which  means  the  two  filk-worms- 
threads  may  be  adjufted  to  a  greater  degree  of  exadlnefs  ;  for  if 
they  are  not  placed  fo  as  perfectly  to  bife6l  the  circle,  the  two 
threads  will  not  coincide  exactly  after  having  performed  one 
femi-revolution,  which  they  muft  be  made  to  do  with  the 
utmoft  rigour.  I  found  the  abfolute  neceflity  of  this  precau- 
tion when'  I  came  critically  to  examine  the  pofitions  of  the 
Georgium  Sidus,  as  they  are  given  in  table  III.  Phil.  Tranf.  vol, 
LXXI.  p.  497.  The  meafures  were  afFeiSled  with  a  fmall  and 
pretty  regular  error,  which  I  was  at  a  lofs  to  account  for  ;  and 
the  diftance  of  this  ft:ar  being  then  totally  unknown,  I  looked 
for  the  caufe  of  the  deviation  at  firft  in  a  diurnal  parallax  of 
that  heavenly  body  ;  but  foon  found  it  owing  to  the  incon- 
venience before-mentioned,  of  not  being  able  experimentally 
to  adjuft  the  moveable  thread  to  that  critical  nicety  which  I 

have 


of  Double  Stars.  i^j 

have  now  introd'accdand  ufed  in  all  the  angles  of  thetollo^ving 


catalogue** 


Datchet  nearWindfor,  Nov.  l,  1784.  W.  HERSCHEL, 


CATALOGUE    0F     DOUBLE     STARS. 
FIRST     CLASS.^ 

I.  25.  A  Ononis.  Fl.  32.     Sob  humero  in  confequentia. 
Jan.  20.      Double.     Confiderably  unequal.     L.  fine  w. ;  S.  w, 

1782.    inclining  to  pale  rofe  colour.     The  diftance  or  black 
divifion  between  the  two  flars  with  278  is  about  \  diar 
meter  of  L.  %  with  460,  near  |  diameter  of  L.     Pofi- 
tion  with  278,  52*  10' f.  preceding. 
26.  fti  Leonis.  Fl.  2.     Anteriorem  pedem  dextrum  praecedens. 

Feb.  8.      A  very  minute  double  ftar.     Confiderably  unequal. 

1782.  Both  r.  With  227  there  is  not  the  leaft  fufpicion  of 
its  being  double;  with  460  it  appears  oblong,  and, 
when  perfedly  diftin(5l,  we  fee  |  of  the  apparent  dia- 
meter  of  a  fmall  ftar  as  it  were  emerged  from  behind  a 
larger  ftar ;  with  932  they  are  more  clear  of  each  other,, 
but  not  feparated ;  the  focus  of  every  power  adjufled 
upon  the  o^^  and  6th  Leonis..     November  6th,   1782,  I 

*  The  divifion s  on  the  moveable  circular  index  (j)  of  this  micrometer  fhould 
be  read  off  by  means  of  a  line  drawn  on  a  fmall  plate  fattened  to  the  fide  /,  and 
projeftiag  with  a  proper  curvature  againft  the  plane  of  the  divifions  towards  r,  fd 
as  to  be  nearly  in  conta<5t;  a  coincidence  of  lines  being  by  far  the  beft  method  of 
afcertaining  the  fituation  of  the  index.  A  nonius  of  four  fub -divifions  may  alfo 
be  ufed,  whereby  the  60  divifions,  already  divided  into  halves  upon  the  index- 
plate,  will  be  had  in  eighths,  each  of  which,  on  the  conflrudion  of  my  prefcnt 
one,  will  be  equal  to  three  minutes  of  a  degree  of  the  circle. 

7  firft 


4^  Mr,  Hf'RsciiEL's  Catalogue 

J.  firfl  fufpcifled  a  feparation  ;   and  November  13th,  fairly 

faw  a  divifion  between  them.  April  4,  1783,  with  an 
improved  refledor  of  20  feet  3  inches  focal  length  and 
12  inches  aperture,  I  faw  them  evidently  divided.  Por- 
tion 20"*  54'  f.  following*. 

2^.  Fl.  90   Leonis.     Infra  edu£i:ionem  caudas. 

Fe^j.  9.       Treble.     The  two  nearefl: — very  unequal.     L.  w. ; 

1782.    S,  rw.     With  2y8,   i^  diameter  of  L;  with  4*^0,    \\ 

diameter  of  L.     Pofition  with  278,  61°  9' f.  preceding. 

The  two   farthefl: — very  unequal.     S.   dufky  r.     Dif- 

tance  from  L.  53'^  43^'^     Pofition  '^^'^  12'  f.  preceding. 

28.  y  Leonis.  Fl   41.     In  coUo  lucida. 

Feb.  II.      A  beautiful  double  ftar.     Pretty  unequal.     L.  w. ; 

1782.   S.  w.  inclining  a  little  to  pale  red.     With  227  and  278 

diftinLlly  feparated  ;  with  460,  4  diameter  of  S.  j  with 

625,   I  diameter;  with  932,  full  I  diameter,  or  when 

*  i  fufpe<5t  thefe  ftars  to  recede  from  each  other.  It  is,  however,  very 
poffible,  that  the  opening  which  I  obferved  between  them,  at  the  latter  end 
of  the  year  1782  and  beginning  of  1 783,  may  be  owing  to  very  favoura- 
ble weather,  or  to  my  being  better  acquainted  with  the  obje£l.  Could  we 
increafe  our  power  and  diflin£lnefs  at  plcafure,  we  might  undoubtedly  fcparatc 
any  .two  ftars  that  are  not  abfolutely  in  a  direft  line  palTing  through  the  eye  of  the 
obferver,  and  the  centers  of  both  the  ftars.  This  will  appear  when  we  confider 
that  perhaps  59  thirds  out  of  one  fecond,  which  the  diameter  of  the  ftar  may 
fubtend,  are  fpurious ;  fo  that  a  double  ftar  feemingly  in  contact,  or  even  partly 
hiding  each  other  in  appearance,  may  ftillbe  far  enough  alunder  to  admit  of  a  fair 
and  confiderable  feparation  by  applying  an  adequate  magnifying  power.  It  would 
have  been  curious,  if  a  confiderable  difference  in  the  colours  could  have  led  us  to 
difcover  which  of  the  two  ftars  is  before  the  other  !  But  the  far  greateft  part  of 
their  apparent  diameters  being,  as  we  have  obferved,  fpurious,  it  is  probable,  that 
a  different  coloured  light  of  two  ftars  would  join  together,  where  the  rays  of  one 
extend  into  thole  of  the  other ;  and  io,  producing  a  third  colour  by  the  mixture 
of  it,  ftill  leave  the  queftion  undecided. 

beft 


Xif  T>otibli  Stan,  49 

I.  bed  I  dinmcter  of  S. ;    with   1504,   I  criamcter,  well- 

defined,  and  the  difference  of  colours  iViU  vifible;  with 
2i;6,  not  quite  a  diameter  of  S,  pretty  well  defined, 
4A,ut  exceedingly  tremulous;  with  2589,  lefs  than  i 
diameter;  with  3168,  ftill  pretty  diilmd,  and  about 
I  diameter  of  S  ;  with  4294,  more  than  a  diamtter  of 
S,  but  attended  with  the  utmoft  difficulty  of  n}anaging 
the  motions  ;  with  5489,  the  interval  fiill  fomewhat 
larger,  and  if  the  obje£l  could  be  kept  in  the  center  of  the 
field,  the  eye  might  adapt  itfelf  to  the  focus,  and 
get  the  better  of  the  violent  aberration  ;  but  J-he  edges 
of  the  glafs  being  of  a  different  focus,  the  eye  is  con- 
ftantly  difappointed  in  its  endeavours  to  define  the  ob- 
je6t ;  with  6652,  I  had  but  a  fingle  glimpfe  of  the  ftar 
^uite  disfigured;  however,  I  afcribe  it  chiefly  to  tho 
foulnefs  of  the  glafs,  which,  on  account  of  its  fmall- 
nefs,  is  extremely  difficult  to  be  cleaned;  withaio-feet 
refle£lor,  9  inches  aperture,  power  626,  above  \  dia- 
meter of  S.  very  diffind ;  with  a  20-feet  reflector, 
power  350,  too  bright  an  obje6t  to  be  quite  diftincly 
though  I  fee  it  very  well.  Pofition  5°  24''  n.  following, 
A  third  fliar  preceding.  Dift.  i^5i^^23'^^,  pretty  accurate 
for  fo  great  a  diffance.  Pofition  31°  o'  n.  preceding.  A 
fourth  ftar  precednig  the  third,  and  fomewhat  fmaller. 

29.  Parvulajuxta  Fl.  44^""  Leonis, 

Peb.  17.      Double.     About  4'  following  the  44LhLeonis,  which 
1782.    being  double  in  the  finder,  this  is  the  lead:  of  the  two. 
Extremely  unequal.     L.  w.  S.  d.     With  227,   14  dia- 
meter of  L. ;  with  460,   2  diameters  of  L.     Pofition 
26°  -2^1'  n,  following. 
Vol.  LXXV.  H  30.  Secunda 


50  Mr,  Herschel's  Catalogue 

I.   30.  Secunda  ad  t  Cancrl.  Fl.  ^y, 

March  <;.      Double.     Pretty   unequal.       Both  pr.       With   227, 
1782.    about  I  diameter;  with  278,   I  diameter;  with  460, 

about  I  diameter  or  lefs.    Poiition  68''  12'  n.  preceding. 

A  beautiful  minute  objetfl:. 

31.  Inter  Fl.  41^""  et  39""  Lyncis. 

March 5.      Double.     Near  i|  degree  n.  preceding  the4ifl:Lyn- 
1782.    cis  ;  towards  ?i  Urfae  majoris.     A  little  unequal.     Both 
w.     With  460,   I  or  at  moft  -*-  diameter,     Pofition  51° 
21'  f.  preceding. 

32.  Fl.  44*  Lyncis  auftralior  et  praecedens. 

April  3.  Double.  About  |  degree  f.  preceding  the  44th  Lyn- 
1782.  cis;  in  a  line  parallel  to  9  Urfse  majoris  and  the  39th 
Lyncis.  Very  unequal.  L.  r. ;  S.  bluifh  r.  With 
227,  I  diameter  of  L.  or  i|  when  beft ;  with  460,  i| 
diameter,  or  when  beft,  near  2  diameters  of  L.  The 
diameters  are  fo  fmall  that  the  length  of  the  time,  and 
attention  of  looking,  makes  a  confiderable  difference  in 
the  eftimation  of  the  diftance.  Poiition  8°  27'  f.  pre- 
ceding. 

33.  £  Librae.  Fl.  51.     Primam  chelam  Scorpii  attingens. 

May  12.  Treble.  Without  great  attention,  and  a  confiderable 
1782.  power,  it  may  be  miftaken  for  a  double  ftar ;  but  the 
largeft  of  them  confifts  of  two.  Very  little  unequal. 
Both  w.  With  460,  I  or  at  moft  -i  diameter  afunder ; 
with  932,  full  I  diameter  of  L.  or  near  |  diameter  of 
S.  Pofition,  with  278,  82°  2'  n.  following.  For 
meafures  of  the  third  ftar  fee  the  20th  of  the  fecond 
clafs. 

34.  Fl.  55.  Caftiopeiae.  <  Ptolemaei.     In  pedis  extremitate. 

Treble 


of  Double  Stars.  51 

I.  Treble.     The  two  neareft  very  unequal.     L.  w. ;  S. 

June  ir,  colour  of  pale  red  blotting  paper.     With  278,  |  diame- 

1782.    terofS.     Pofition  with  227,  20"  30^  n.  preceding.    For 

mealures  of  the  third  ftar  fee   the  fourth   in  the  third 

clafs. 

35.  Fl.  38..  Serpentarii.     Dextrum  infra  pedem. 

June  I  r,       Double.     Very  unequal.     L.  w. ;  S.  d.     With  460, 
1782.     1 1  diameter  of  L.     As  the  fituation  is  too  low  for  460, 
I  tried  227,  but  it  only  fhewed  the  flar  wedge-formed. 
Pofition  60°  48^  n.  preceding. 

36,  ^Herculis.  Fl.  40.     In  dextro  latere. 

July  18,      A  fine  double  flar.     Very  unequal.     L.  w. ;   S.  afli- 
1782.    colour.     With  460,  lefs   than  §  diameter  of  S.  ;  with 
932,    I    full    diameter   of    S.  *.      Pofition  with   811, 
20^42'  n.  following. 
^7.  (p  (Fl.  1 1^.")  Herculis  borealior  et  fequens. 
July  22,      Double.     About  j  degree  n.  following  <p ;  in  a  line 
1782.    parallel  to  the  35th  and  42d  Herculis;  the  mofl:  fouth 
of  two  very  fmall  telefcopic  ftars.     Confiderably  une- 
qual.    Both  reddifh.     V/ith  227,  they  can  but  juft  be 
feen   as   two  ftars ;  with   460,  near   i    diameter ;  with 
932,  not  lefs  than  i|  diameter  of  L.     Pofition  59*^48' 
f.  following. 

*  The  interval  between  very  unequal  ftars,  eftinaated  in  diameters,  generally 
gains  more  by  an  increafe  of  magnifying  power  than  the  apparent  diftancc  of  thofe 
which  are  nearer  of  a  fize.  Inftances  of  the  former  may  be  found  in  the  firft 
clafs,  the  ift,  7,  29,  35,  37,  39,  53,  59,  63,  64,  72dilars;  of  the  latter,  the 
i6th,  28,  33,  45,  46,  73,  Siftftars.  However,  this  only  feems  to  take  place 
when  there  is  a  difficulty  of  feeing  the  objeft  well  with  a  low  power,  which  being 
removed  by  magnifying  more,  the  diftance  is,  ns  it  were,  laid  open  to  the  view. 

H  2  38.  Fl. 


52^  Mr,  Herschel's  Cafaloguf 

I.  38.  Fl.  18'"^  Perfei  pra^cedens  ad  boream.  In  capite; 
Aug.  20,  Double.  About  |  degree  n.  preceding  the  i8th;  m 
i;82.  a  biie  parallel  to  o-  and  r  Perfe'ij  of  two  ftars- that 
next  to  the  1 8th.  A  little  vmequal.  Both  pr.  With 
278,  a  moil:  minute  and  beautiful  objecl ;  with  460, 
I  diameter  of  either.  Pofitioii  with  278,  ^.^  42'  rib. 
preceding. 

39.  jG  (Fl.  ii*"")  Caffiopeiic  prgecedens  ad  auftrum. 

Aug.  25,  Double.  About  I  degree  f.  preceding  /G ;  in  a  line 
1782.  parallel  to  17  and  a  CaliiopeiLC  ;  the  following  and  largeft 
of  two  very  confiderable  flars.  Very  unequal.  L. 
pr. ;  S-.  r.  With  278,  |  diameter  of  S; ;  with  460, 
f ,  or  when  beft,.  |  diameter  of  S.  Polition  50°  42'  it. 
preceding. 

40.  Fl.  25""  Caiilopeiae  pr^ecedens  ad  boream. 

Aug.  28,      Double.     About   f'   degree   n,   preceding  the    2£;tlir 
J 782.    towards    a   Caliiopeias ;-   the  firfl:  telefcopic  flar  in  that 
diredion.     Very  unequal.     Both  r.     W^ith  460,   |  dia- 
meter of  S. ;  difficult  to  be  feen.     Pofition  50°  ^o'  f,. 
following. 

41.  Fl.  ^i^Draconls  boreaiior. 

Aug.  29,  A  very  minute  double  ftar.  About  |  degree  n.  of  the- 
1782.  3ifti  ii^  ^  lii^s  parallel  to  y  and  ^  Draconis;  the  moft 
louth  and  preceding  of  two.  Confiderably  unequal. 
Both  pr.  or  r.  With  227,  they  appear  only  as  a 
lengthened  or  diflorted  flar  ;  with  460,  I  diameter  of 
S. ;  or  in  very  fine  nights  f  diameter  of  S. ;  with  a. 
new  fpeculum  and  <;oo,  near  f  diameter  when  beft;- 
with  9^2,  f  diameter.  Pofition  84°  21''  n.  preceding. 
Requires  qyqyj  flivourable  circumftaace  to  be  €tQi\ 
double. 

3  42- 


of  Double  Stars,-  5J 

I,  42.  ^Serpentls.  Fl.  13.     In  primo  flexu  colli. 
Sept.  ",      A  beautiful  double  ftar.     Coniiderably  nneq\3al.     L» 
1782.    vv. ;  S.   greyidr.     With   227,  \  diameter  of  S. ;  with 

278,  not  quite    |   diameter  of  S. ;  with   460,  near  i 

diameter  of    S. ;    with    932,  near    i    diameter  of  S.  ; 

with  1504,  above  i  diameter  of  S,     Polition  42°  48'  1^ 

preceding, 

43.  Ad  Fl.  48*'^^  Draconis. 

Sept.  --,  A  very  minute  double  {lar.  The  moH  north  of 
1782.  three,  forming  an  arch  ;  or  that  which  is  towards  a 
Draconis.  Confiderably  unequal.  Both  pale  pink.  In 
fine  nights,  with  460,  it  has  the  fliape  of  a  wedge;; 
with  932,  a  fine  black  divifion  juft  vifible ;  in  a  very- 
clear  dark  night  a  divifion  may  be  ittw  with  500,  and 
with  9:52,  it  will  be  about  4.  diameter.  Polition  witl> 
500,  88°  24^  n.  preceding. 

44.  Fl,  4.  Aquarii.     Supra  veftimentum  manus  finiflrae. 

Sept.  3,       A   minute    double    flar.     Very  unequal.     Both   pr. 
1782.    With  460,  almofl:  in   contadl,  or  at  moft  4.  diameter 
of  S.     Pofition  81°   30'  n.   preceding.     A  third  flar  of 
the  fixth  clafs  in  view,  n.  preceding. 

45.  ^  Aurigae(FL.  11*"')  pr^ecedens  ad  auftrum. 

Sept.  5,  Double.  About  1 1  degree  f.  preceding  ^^  towards- 
1782.  i  Auriga  y  a  pretty  confiderable  fliar  in  a  minute  tele- 
fcopic  conftellation.  A  little  unequal.  Both  pr.  or  r, 
W^ith  227,  I-  diameter  of  S. ;  with  278,  near  1  dia- 
meter of  S. ;  with  460,  about  f  diameter,  or  near  § 
Jiameter  of  S.     Pofition  47°  ^^.  f.  preceding, 

46.  V  (Fl.  13''")  Aquarii  fequens  ad  boream. 

Sept.  7.       Treble.     About   1 1   degree  n.  following  v,  m  a  line 
1782.    pcirallel  to  /3  and  oe,  Aquarii;  the  middle  of  three  that 

ars 


5?J.  Mi\  HEnscEEL^  Cafa/ogug 

I.  are  in  .the  fame  diredion.     The  two  neareft  very  une- 

qual. L.  rw.  ;  S.  pr.  With  460,  about  i  diameter 
of  L.  or  more.  Pofition  62°  27'  n.  preceding.  The  two 
fartheft  very  unequal.  S.  pr.  Diftance  with  227, 
1^  22'^  42^^^     Pofition  35°  51'  n.  following. 

47.  Fl.  29'"^  Capricorni  prascedens  ad  bor-eam. 

Sept.  27,  A  minute  double  ftar.  About  |  degree  n.  preceding 
1^82.  the  29th,  in  a  line  parallel  to  y  and  a  Capricorni.  A 
little  unequal.  Appears  diflorted  with  227  and  278; 
nor  will  460  (hew  it  feparated  ;  with  657,  two  ftars 
vifible  ;  932  confirms  it.  Difficult  to  be  feen  diftindly 
on  account  of  its  low  fituation.  Pofition  84°  48'  n. 
preceding.     20-feet  refle(5lor,    200.     Both  w. 

48.  Fl.  6*'"  Cephei  praecedens.     In  dextro  brachio. 

Sept.  27,      Avery  minute  and  beautiful  double  ftar.     Near  |  de- 

^1782.  .  gi'GS   preceding  the    6th   towards  1; .  Cephei ;    a  pretty 

fconfiderableteiefcopic  ftar.     A  little  unequal.     Both  pr* 

Almofl  in  contact  with  460;  with  625,  better  divided; 

with  657  ftill  better.     Pofition  14°  9''  f.  preceding. 

49.  X  Cephei  (Fl.  22^"")  fequens  ad  boream. 

Sept. 27,  Double.  About  i|  degree  n.  following  X,  in  aline 
1782.  fiom  ^through  X  Cephei  continued.  Extremely  une- 
qual. Both  dw.  Cannot  be  feen  with  278,  except 
with  long  attention;  with  460,  if  diameter  of  L. 
Pofition  85°  48'  n.  following;  perhaps  a  little  inac- 
curate. 

c;o.  X  Aquarii  (Fl.  y^"""")  prfficedens. 

Sept.  30,      Double.     About   2f    degrees  preceding,  and  a  little 

1782.    fouth  of  X  Aquarii;  a  confiderable  ftar.     Very  unequal. 

■L.  w. ;  S.  dw.     With  278,  lefs  than    i   diameter  of 

L;  with  460,  1 1  diameter  of  L.     Pofition  with  227, 


41^ 


of  Double  Slavs.  ^  r 

I.  41'   12'  n.   preceding.      The    meafnre   inaccurate  on 

account  of  the  low  power,  and  probably  3°  or  4°  too  . 
fmall. 

51.  Quas  fequitur  i  (Fl.  32*"")  Cephei. 

Sept.  30,      Double.     About  2I  degrees  n.  following  <,  towards 
1782.    y  Cephei;  a  confiderable  jftar.     A  little  unequal.     Both 
pn     A  pretty  object  with  227;  with  460,   i|  diameter 
nearly.     Pofition  3°  36'  f.  preceding. 

52.  Parvula  Fl.  25"'Orionis  adjecla. 

oa.  2,       Double.     A    few  minutes   n.   following    the    25th 
1782.    Orionis,  in  a  line  parallel  to  h  Eridani  and  e  Orionis. 
Very  unequal.     L.  afh  w. ;  S.  dw.     With  460,   i  dia- 
meter of  L.     Pofition  52°  48'  n.  preceding.  . 

53.  Parvula  Fl.  30""^  Orionis  adjeda. 

oa.  2,       Double.     About    10^  preceding  the  30th,  in  a  line 
1782.    parallel   to  X   and  y  Orionis.     Very  unequal.     L.  w. ;  .: 

S.  d. ;  with  460.,   i  diameter  of  L.     Pofition  43°  24'  n. , 

following. 

54.  T  (Fl.  20**")  Orionis  praecedens.  In  malleolo  liniftri  cruris, 
oa.  4,  Double.  Near  |  degree  preceding  r,  in  a  line  from 
1782.    ^  through  T  Orionis  continued.     Very  unequal.     L.  r. ; 

S.  dr.     With  227,  about  1  diameter  of  L. ;  with  460, 
about  2  diameters  of  L.     Pofition  35°  42'  n.  preceding; 
a  little  inaccurate. 
^^,  Fl.  8""  Tauri  praecedens  ad  boream.  . 
oa.  g.       Double.    '  About    i  j    degree  n.   preceding  the    8th 
1782.    Tauri,  or  near  2  degrees  f.  following  the  65th  Arietis, 
in  a  line  parallel  to  the  Pleiades  and  e  Tauri;  a  fmall 
telefcopic    flar   not   eafily   found.      A   little   unequal. 
L.  r»;  S.  d.  _  With  227,  lefs  than   1    diameter  of  S. ;  ; 

with  . 


5-6  Mr.  Herschel's  Catalogue 

L  with  460,  near   two   diameters.     Pofition  82*  48'   {. 

following. 
56.  Fl.  54^""  Ceti  fequens  ad  an  drum, 

06l.  12,      Double.     About    |    degree   f.   following  the    54th, 
1782..    towards  <5"  Ceti.     Nearly  equal.     Both   r.     With  227, 
about  I  diameter;,  with  460,  about  il  diameter.     Po- 
fition 87°  39'  n.  following. 
^'j.  Fl.  70^""  et  67'"^  Orionis  pra^iens. 

061.12,      Multiple.     In  a  fpot  which  appears  nebulous  in  the 
1-782.    finder,  and  is  about  50'  fi-om  the  67th,  and  45^  from 
the  70th  Orionis.     More   than  1 2  ftars  in  view  with 
460  ;  among  them  is  a  double  ftar.     The  largeft  of  the 
bafe  of  an  ifofceles  triangle,  e.  preceded  by  four  ftars  in 
a  line.     Conliderably  unequal.     With  460,   i  full  dia- 
meter of  L.     Pofition  19°  48'  f.  following.. 
38.  ^  Lyrae  (Fl.  12*"')  fequens.     Inter  edu(9:ionem  cornuum, 
Oft.  24,      Double.     About   f  degree  following  the  12th,  in  a 
J782.    line  continued  from  the  11   through  the  12th  Lyra:; 
the  lafi-  of  a  finall  telefcopic  triangle.     Extremely  une- 
qual.    L.  r. ;  S.  d.     Not  eafily  feen  with  227  ;  with 
460,  near  2  diameters  of  L.     Pofition   i^°  o'  n.  pre- 
ceding. 
^().  Ab  I  (Fl.  18')  Lyras /3verfus. 

oa.  24,  Double.  The  moft  fouth  of  two  very  fmall  tele- 
11782.  fcopic  ftars,  which  are  the  fecond  pair  fituated  in  a  line 
from  I  towards  jG  Lyrae.  A  little  unequal.  Both  d. ; 
the  fainteft  object  that  can  be  imagined.  With  460, 
about  I  diameter.  Pofition  y c^^  o'  f.  preceding;  the 
meafure  is  liable  to  fome  error  from  the  obfcurity. 
60.  E  telefcopicis  7/  et  X  Lytic  auftralioribus  ct  fcquentibus. 

Double 


of  Double  Stan,  57 

I. 

oa.  24,       Double.     About   |  degree  X   following  x,  la  a  Hue 

1782.  parallel  to  a  and  'y  Lyrae;  a  very  fmall  tclefcopic  ftar. 
Extremely  unequal.  Both  dr.  With  227,  i  full  dia- 
meter of  L ;  with  4.60,  near  2  diameters  of  L.  Poii- 
tion  16^  48'  n.  preceding. 

6r.  Pra^iens  Fl.  i^'^' Equulel. 

oei.  26,       A  minute  double  flar.     About  |  degree  n.  preceding 
1782.    the    ifl:   Equulei,  in    a   line  parallel   to   «   Equuiei  and 
y   AquilcC ;    a,  large  fl:ar.       Very   unequal.     Both   pr. 
With  460,   I   diameter  of  S.     Pofuion   18^  24'  n.  pre- 
ceding.    A  pretty  obje6l,  but  requires  fine  weather. 

62.  Sequitur  Fl.  2^"'  Equuiei.. 

oa.  29,       Double.    About  |  degree  f.  following  the  2d  Equuiei, 
1782.    in  a  line  parallel  to  I  Delphini  and  (5*  Equuiei.     Conii- 
derably  unequal.     Both   r.     With  460,    il  or  !|  dia- 
meter of  S.      Pofition  35°  9'  f.  preceding. 

6'^,  y  Equuiei  (Fl.  5^)  auftrallor. 

oa.  29,       Double.     Full  I   degree  f.  of  7,  in  a  line  fi-om  the 
L782.    5th  through  the  6th  Equuiei  continued.    Equal.     Both 
dr.     With  227,  about  I   diameter  fcarce  vifible ;  with 
460,  about  I  diameter.     Pofition  5^  ^j'  f.  preceding. 

64.  TT  x\rietis.  Fl.  42.     In  poplite. 

oa.  29,  Treble.  Exceffively  unequal.  L.  w ;  S.  both  mere 
1782.  points.  With  227,  neither  of  the  fmall  ftars  can  be 
itQw,  except  with  confiderable  and, long  continued  atten- 
tion, when  .they  alfo  appear;-  the.  neareft  with  this 
power  is  |  or  1.  diameter  of  L. ;  with  460,  1 1  or  1 1 
diameter  of  L.  The  third  is  about  25^''  or  16'^  dlftant 
from  L,  by  exa£t  eflimation.  Pofition  of  both,  being 
all  three  in  a  line  19°  19^  f.  following;  as  exacl  as  the 
obfcurity  will  permit. 
V0L.  LXXV.  I  6s^ 


^8  Mr.  Herschel's  Catalogue 

I.  65.  Ill  Nubecula  /3  Sagitt;^  adjecla  et  fequenti. 

Nov.  4,  Double.  I  degree  n.  following  /3  Sagittie,  towards 
1782.  2  9tli  Vulpeculs  ;  the  largefl  and  moiL  fouth  of  a  clufter 
of  fmall  ftars  that  appear  cloudy  in  the  finder.  Very 
unequal.  L.  rw.  ;  S.  pr.  With  22^,  full  i  diameter 
of  L.  ;  with  460,  about  1 1  or  2  diameters  of  L.  Po- 
fition  14°  o'  n.  preceding.  A  third  flar  in  view,  of  the 
5th  or  6th  clafs. 

66.  /3  (Fl.  23^)  Draconis  auftralior  et  prsecedens. 

Nov.  4,       Double.     About  1 1  degree  f.  preceding  /3,  in  a  line 
1782.    from   V  continued  through  ^   Draconis.     Pretty  une- 
qual.    Both  pr.     With  460,   1 1  or  1 1  diameter  of  L. 
Poiition  a°  24'  f.  preceding, 

6y.  Nebulam  Aurigas  pedem  dextrum  fequentem,  priccedens. 

Nov.  4,       Double.     About  55'   from  the  37th  Nebula  of  M, 

1782.  Messier  ;  the  largeft  and  mod  preceding  of  two  flars. 
Very  unequal.  Both  pr.  With  460,  near  2  diameters 
of  L.     Poiition  23°  57^  n.  following. 

68.  Parvula  Fl.  io'^  Orionis  quam  proxime  adjecla. 

Nov.  5,       Double.     The  fmall  ftar  not  many  minutes  from  the 
1782.     loth  Orionis.     A  little  unequal.     Both  whitifh.    With 

460,  near  i  diameter.     Poiition  84°  54'  f.  following; 

a  little  inaccurate  on  account  of  the  difficulty  of  feeing 

the  ftars  well. 

69.  In  Lyncis  pedlore. 

Nov.  13,      Double.     About   3   degrees   f.   preceding  the    19th 

1782.    Lyncis,  in  a  line  drawn  from  the  19th  Lyncis  to  t  Au- 

rigas ;  the  24th  and  19th  Lyncis  alfo  point  to  it  nearly  : 

in  a  very  clear  evening  it  may  juft  be  feen  with  the 

naked  eye.     A  little  unequal.     Both  rw.     With  227, 

I  dia- 


of  Double  Suj?s.  :^g 

I.  I  diameter  ;  with  460,   i  ^  or  near  1 1  diameter.     Poii- 

tioii  77^  o'  f.  following. 
70.  f  (Fl.  1235)  Tauri  borealior  et  prxcedens. 

Nov.  13,  A  very  pretty  double  ftar.  Near  i  degree  n.  pre- 
1782.  ceding  f  Tauri  towards  Capella  ;  the  corner  of  a  rhom- 
boid made  up  of  (^,  this,  and  two  more,  and  oppofite 
to  ^.  Confiderably  unequal.  '  L.  pr. ;  S.  a  little  deeper 
r.  With  227,  almofi  i  diameter  of  L.  ;  with  460, 
1 1  diameter  of  L.     Pofition  36"  24^  f.  preceding. 

7*.  Fl.  44'""  Urfas  majoris  priccedens  ad  auftrum. 

Nov.  1 9,  Double.  Nearly  in  the  interfection  of  a  line  from 
1782.  iG  Urfi£  majoris  to  the  39th  Lyncis,  crofled  by  one  from 
4^  to  u  UrfcE  majoris  ;  the  lafh  line  fhould  bend  a  little 
towards  t1>  Urf^  majoris.  A  little  unequal.  Both 
whitilh.  With  460,  near  2  diameters  of  S.  Pofition 
2^  6^  n.  following. 

72.  Fl.  6^,  Urfse  majoris. 

Nov.  20,  Double.  Excefiively  unequal.  L.  pr. ;  S.  a  point. 
1782.  Not  vifible  with  227,  nor  hardly  to  be  fufpe£l:ed  unlefs 
it  has  been  firft  feen  with  a  higher  power ;  with  460, 
1 1  diameter  of  L.  or,  when  long  viewed,  full  z  dia- 
meters of  L.  Polition  53°  45'  n.  following.  A  third 
ftar  in  view.  Equal  to  L.  Colour  rw.  Diftance 
i'  o'^  4'^'.     Pofition  22"  21'  f.  following. 

y^,  jQ  (Fl.  6")  Arletis  borealior  et  prsecedens. 

Nov.  22,      Double.     About    1 1    degree  n.  preceding  /S  Arietis, 
1782.    towards /3  Andromedse  ;  a  confiderable  ftar.    Very  une- 
qual.    L.   r.  ;  S.  deeper  r.     With   227,  about  |    dia- 
meter of  L. ;  with  460,  full  i|  or  almofi:   if  diameter 
of  L.  when  beft.     Pofition  yy^  24'  f.  following. 

I  2  74. 


6o  Mr.  HercCKEl's  Catalogue- 

I.  74.  Fl.  39^  i\rietis  borealior  et  prascedens. 

Dec.  22,      Double.     About   |    degree  n.   preceding  39  Arletis, 

1782.  towards  <)/ Triaiiguli ;  a  pretty  large  telefcopic  ftar,  A 
little  unequal.  Both  pr.  Witli  227,  near  i  diameter 
of  L. ;  with  460,  about  i§  diameter  of  L.  Politloa 
20°  36^  n.  preceding. 

75.  Fl.  26''""  Orionis  prxcedens  ad  auftrum. 

]an.  9,       Double.     About  I  degree  f.  preceding  the   26th,   ia 
1^83.    ^  liiie  parallel  to  (5" and  /3  Orionis;  the  tartheft  of  two  ;, 

or  I  degree  f.   preceding  the  30th  in  the  fame  direction. 

Nearly  equal.     Both  w,  or  r\v.      With  460,  perhaps  a 

diameter.     Pofition  89°  36'  n.  preceding;  but  not  very 

accurate. 

76.  In  pe£lore  Lyncis. 

Tall.  23,  Double.  Not  eafy  to  be  found.  A  line  from  the  19th* 
178^.  Lyncis  to  u  Geminorum  eroded  by  one  from  Q  Urfic 
majoris  to  e  Auriga^,  points  out  a  ifar  but  juil;  viliblejn 
a  fiiie  evening;  it.  is -perhaps  about  three  degrees^from 
the  19th  Lyncis;  when  that  flar  is  found,  w^e  have  the 
double  ftar  about  i  degree  11.  following  the  fame,  in  a 
line  parallel  to  r  Geminorum  and  the  19th  Lyncis. 
Confiderably  unequal.  Both  afh  w.  ,  With  460,  I 
diameter  of.  S.  Pofition  o'  o'  preceding.  A  third 
laroe  ftar  ill' view.  .Diftance  1/  i'[  46'^'.-  Pofitioa 
3^  42'  f.  preceding, 

7*^.  K  (Fl.  7^)  Crateris  borealior. 

Tan.  31,      Double.     Near   2|    degrees   north  of  a    Crateris;  a 

1783.  fmall  telefcopic  fiar,  about  I  degree  following  the 
mod  north  of  two  large  ones.  Pretty  unequaL  Both 
whltifn.     With   227,  iefs    than  half  diameter   of  S. ; 

with 


of  Double  Stars.  6 1 

I.  with  460,  near    i    diameter;  with   625,  a   little  more 

than  I  diameter.     Poiition  82^  2\'  n.  following. 

78.  Fl.  I  i^  Librae  borealior. 

Jan.  31,       Double.     Near  2|  degrees  north  of  the  i  ith  Librae, 

1783.    in   a  line  parallel  to  |W   Virginis  and  the  109th  of  the 

fame  conftellation.    Equal.    Both  inclining  to  r.    With 

460,  full  I    diameter.     Poiition  58^  24'  n.  preceding, 

or  f.  following. 

79.  Fl.  46  Herculis.     In  dextro  latere* 

Feb.  5,       Double.     Extremely  or   almoft  exceflively  unequal. 

17S3.    L.   w. ;  S.   d.     With  227,  it  is    hardly  vifible  ;  with  • 
460,  near    i    diameter  of  L.     Pofitlon  66^  36'  f.  fol- 
lowing. 

80.  Fl.  81  Virginis. 

Feb.  7,       Double.     Equal.     Both  pr.     With  227,  near  1  dla- 
1783.    meter;  with  460,   f  diameter.     Pofition  41*^  12^  n.  fol- 
lowing or  f.  preceding. 

81.  TT  Serpentis  (Fl.  44^"")  prascedens  ad  auflrum. 

]Mar. 7,       Double.     About  i\    degree  f.  preceding  tt,  towards 
1783.    k;  the  mofl:   north   of  two.  A    little  unequal.     Both 

r.     With  460,   If  diameter  of  L.     Pofition  49°  48^  f. 

preceding.     A  third  large  ftar  in  view  ;  paler  than  the 

other  two.     Diftance  from   the  two  taken  as  one  ftar 

56''   28'''.     Pofition,  with  L.   of  the  two,  31°  48' f. 

preceding. 
S-2.  Fl.  49  Serpentis. 

Mar.  7,       Double.     The    moft   north    and  •  following  of   two 
1783.    ftars.     A  little  unequal.     Both  pr.     With  227,   I  or  I 

diameter,    and    a  very  minute   and    beautiful    object ; 

with  460,  ■  I  diameter.     Pofition  21°  ^^'  n.  preceding. 
3  S3' 


'62  AI .  ^"terschel's  Catalogue 

1.83.  A  Ophiuchi.  Fl.  10.     In  ancone  fiQlilri  brachii.  ^ 

M^v.  9,       A  very   beautiful   and  ciofe  double  ftar.     L.  w.  ;  S. 
1783.    blue;  both  fine  colour?      Conliderably  or  almoil:  very 
unequal.     With   460,  |    or   J-    dinmeter  of  S.  ;   with 
932,  full    }  diameter  of  S.     Ponlion    14°   30^  n.   fol- 
lowing. 

84.  Fl.  ^o^  Aung2e  auftralior. 

Mar.  18,      Double.     Near   i   degree  f.  of  the  50th  Auriga^,  in 

1783.    a    line  parallel   to    /3  and  0.      Very  unequal.      L.   r.  ; 

S.    dr.     With   227,    about    I    diameter    of   L. ;    with 

460,    almoftj  i^  diameter  of   L.     Pofition    14°  o'   n. 

following. 

85.  Fl.  36^""  Lyncis  fequens  ad  auftrum. 

Mar.  24,  Double.  Near  f  degree  f.  following  the  36th  Lyn- 
1783.  cis,  in  a  line  parallel  to  the  31  ft  Lyncis  and  n  Urfte 
majoris  ;  of  two  the  neareft  to  the  31ft  Lyncis.  Con- 
fiderably  unequal.  Both  w.  With  227,  i  diameter  of 
L. ;  or  when  long  kept  in  view,  1 1  diameter  of  L. ; 
TOth  460,  and  after  long  looking,  2  diameters  of  L ; 
otherwife  not  near  fo  much.  Pofition  88°  57'  n.  fol- 
lowing. 

86.  Fl.  105^  Herculis  borealior. 

Mar.  27,     Double.     One  full  degree  n.  of  the   105th  Herculls, 

1783.    in  a  line  from  the  72d  Serpentarii  continued  through  the 
105th  Herculis  ;  a   fmall  telefcopic  flar.     Confiderably 
unequal.     Both  dr.      With  460,  a  little  more  than  i 
diameter  of  L.     Pofition  'j^°  z/\!  n.  preceding. 
tj.  q  Ophiuchi.  Fl.  y^. 

April  27,     A  very  minute  double  ftar.  Confiderably  unequal.  L.  r. 

1783.    S.  r.     With  227,  not  to  be  fufpe<5led  unlefs  known  to 

be  double,  but  may  be  feeii  wedge-formed,  and  with 

6  long 


of  Double  Slurs,  6q 

L  long  attention  I  have  alfo  perceived  a  mofl  minute  divi- 

fion  ;  with  460,  about  |  or  }  diameter  of  S.     Pofition 
2°  48^  f.  preceding. 

88.  T  Ophiuchi.  Fl.  69.     In  dextra  manu  fequens. 

April  28,  The  clofefl  of  all  my  double  ftars  ;  can  only  be  fuf- 
17S3.  pe6led  with  460;  but  932  confirms  it  to  be  a  double 
ftar.  Pretty  unequal.  Both  pr.  or  wr.  It  is  wedge- 
formed  with  460;  with  932,  one-half  of  the  fmall 
ftar,  if  not  three- quarters  feem  to  be  behind  the  large 
ftar.  Pofition  of  the  wedge  61°  36'  n,  preceding. 
V  Ophiuchi,  jufl:  by,  is  perfectly  free  from  this  wedge- 
formed  appearance. 

89.  Illas  ad  Fl.  56*""  Andromcdae  praecedens  ad  boream. 

July  28,      Double.    About  f  degree  preceding,  and  a  little  north 

1783.  of  the  two  ftars  that  are  about  the  place  of  the  56th  An- 
dromeda, in  a  line  towards  j«;  a  conliderable  ftar;  and  of 
two  in  a  line  parallel  to  (3  and  y  Trianguli  that  which 
is  nearefl  to  the  56th  Andromedse.  Pretty  unequal. 
L.  drw. ;  S.  dpr.  With  227,  near  i  diameter  of  L.  ; 
with  460,  about  i|  diameter  of  L.  Pofition  75°  30' 
f.  following. 

90.  jQ  Aquarii  (Fl.  22^"")  praecedens  ad  auflrum. 

July  31,      Double.  About  4 1  degrees  from  jG  towards  ^  Aquarii. 

1783.    A  little    unequal.     Both   dw.   or  pr.     With    460,   li 

diameter  or  near  2.     Pofition  77°  36^  £  following. 

91.  y  Aquilae  (Fl.  50^''')  praecedens  ad  boream. 

Aug.  7,      Double.     About  f  degree  n.  preceding  7,  in  a  line 

1783.    parallel  to  y  and  ^  Aquilas;  of  two  that  nearefl  to  y. 

Very  unequal.     L.  dpr.  ;    S.  d.     With   227,    hardly 

vifible,  and  like  a  ftar  not  in  focus;  with  460^  appears 

nebulous 


64'  '^^'  Herschel's  Catalogue 

I.  nebulous  on  one  fide,  but  is  a  double  flar;  with  932,. 

about  i\  diameter  of  L.     Pofition  8°  18'  n.  preceding. 

92.  17  Aquilae.     Fl.  52.     Duarum  in  finiftro  humero fequens. 
Aug.  27,     A    minute  pretty   double    flar.       A   little   unequal. 

1783.    Both  pr.     With  460,  f  diameter  of  L.  or  near  %  dia-, 
meter  of  S.     Pofition  34.°  24^  f.  following. 

93.  Fl.  62^"™  Aquilas  prcecedens  adboream. 

Sept.  12,  A  minute  double  fiar.  About  |  degree  n.  preceding 
1-83.  the  62d,  in  a  line  parallel  to  ^  and  J'Aquilce;  a  pretty 
confiderable  ftar.  Very  unequal.  Both  inclining  to  pr. 
With  278,  almoft  in  conta6t ;  with  460,  near  |  dia- 
meter of  S. ;  when  in  the  meridian,  and  the  air  fine, 
near  i  diameter  of  L.     Pofition  19°  9'  n.  preceding. 

94.  ^  Cygni.  Fl.  i  8.     In  ancone  alas  dextrae. 

Sept.  20,  Double.  Very  unequal.  L.  fine  w. ;  S.  afh  colour 
2783.  inclining  to  r.  With  27S,  about  \  diameter  of  L. ; 
with  460,  I  diameter  of  L. ;  with  932,  full  i|  dia- 
meter of  L.  in  hazy  weather,  which  has  taken  off  the 
rays  of  L.  and  and  thereby  increafed  the  interval. 
Pofition  18°  -21^  n.  following;  perhaps  a  little  inac- 
curate. . 

95.  Fl.  2)3'''^  Cyg^^i  fequens  ad  au drum. 

Sept.  22,  Double.  Full  1 1-  degree  f.  following  the  33d, 
1783.  towards  J  Cygni ;  a  pretty  confiderable  ftar.  Very  une- 
qual. L.  w.  ;  S.  inclining  to  r.  With  460,  at  firfl 
about  f  diameter  of  L. ;  but,  after  looking  a  confidera- 
ble tinae,  and  in  a  fine  air,  near  \\  diameter.  Pofition 
72°  15'  n.  preceding. 

96.  ?j  (Fl.  zi''")  Cygni  fequens  ad  aufirum, 

Sept.  23,     Treble.     Full    i|    degree  n.  following  ij,  in  a  line 
i!783,    parallel  to  Q  and  A  Cygni,    The  two  neareft  confiderably 

unequal. 


of  Double  Stars,  6$ 

I.  unequal.  Both  pr.  With  460,  i  diameter  of  S.  or  | 
diameter  of  L.  Pofitioii  89°  18'  f.  following.  The 
two  farthefl:  confiderably  unequal ;  the  colour  r.  Did. 
Pofition  56°  3'  n.  preceding. 

^y.  Fl.  51*"  Cygni  fequens. 

Sept.  24,  A  minute  double  ftar.  About  2I  degrees  following 
1783.  the  5 1  ft,  in  a  line  parallel  to  ^  and  a  Cygni ;  the  largeft 
and  moft  fouth  of  an  obtufe-angled  triangle ;  a  very 
confiderable  ftar.  Pretty  unequal.  Both  rw. ;  but  S. 
a  little  darker  r.  With  278,  |  diameter  of  S.  and 
beautiful ;  with  460,  |  diameter  of  S.  Pofitioii  46" 
24'  n.  following.  v 


SECOND    CI^ASS    OF    DOUBLE    STARS. 

II.  39.  Procyonem  juxta. 
Feb.  2,  Double.  About  2  degrees  f.  following  Procyon,  in 
1782.  a  line  froni  \  Geminorum  continued  through  Procyon. 
Exceflively  unequal,  L.  pr. ;  S.  not  vifible  with  278  ; 
with  460,  more  than  3  diameters  of  L.  Pofition,  by 
the  affiflance  of  a  wall  *  and  micrometer  54^  28'  fl 
following. 

40. 

*  When  the  fmall  ftar  is  fo  faint  as  not  to  bear  the  leafl  illumination  of  the 
wires,  its  pofition  may  flill  be  mcafurcd  by  theafilfranceof  fome  wall  or  other  obje6l; 
for  an  eye  which  has  been  fome  time  in  the  dark,  can  fee  a  wall  in  a  flar-hght 
evening  fufficiently  well  to  note  the  projection  of  the  Hars  upw  it,  in  the  manner 

VOL.  LXXV  K  which 


66  Mr.  Her scH el's  Catalogui 

11.   40.   *  Secunda  ad  (?;  Cancri.  Fl.  23. 

Fe:^.  2,       Double.     A  little  unequal.     Both  nv.     With  227,, 
J782.    near  2  diameters ;  with  460,   2-2-  diameters  of  L.     Po- 
fition  56°  42''  n.  following. 

41.  *  Prima  ad  v  Cancri.  Fl.  24. 

Teh.  2,       Double.      Confiderably  unequal.      Both   pr.     With- 
1782.    227,   1 1  diameter  of  L. ;  with  460,  4  diameters  of  L. 
Pofition  32^  9'  n.  following, 

42.  E  telefcopicis  k  Virginis  precedentibusf. 

Feb.  6,  Double.  i\bout  1 1  degree  f.  preceding  k  Virginis, 
1782.  ill  ^  line  parallel  to  f  and  ^;  the  moft  fouth  of  three 
forming  an  arch.  Extremely  unequal.  L,  w. ;  S^ 
hardly  vifible  with  227  (but  with  a  ten-feet  refle£lor 
S.  b.)  ;  with  460,  above  2  diameters  of  L.  Pofitioa 
52°  24^  f.  following. 

43.  Fl.  43''"  Leonis  praecedens  ad  auftrum.     In  dextro  genu. 
Feb.  17,     Double.     Near  f   degree  f.  preceding  the  43d,  in  a 
1782.    hne  parallel  to  c<,  and  the  14th  Leonis.     Very  unequal. 

L.   w. ;  S.  d.     With    227,  near    2|    diameters  of  L,. 
W'hen  heft.     Pofition  85°  2'  n.  following. 

44.  0  Virginis.  Fl.  84.     Verfus  finem  alse  dextra^. 

Feb.  17,     Double.     Extremely  unequal.    L.  w.  incUning  to  r.  ; 
1782.    S.  d.     Requires  attention  to  be  feen  with  227;  with. 

460,  2i   diameters  of  L.     Pofition,  with  278,  29°  5' 

f.  preceding. 

which  has  been  defcribed  with  the  lamp-micrometer,  Phil.  Tranf.  vol.  LXXII.  p. 
269  and  170.  Then,  introducing  fome  light,  and  adapting  the  fixed  wire  to 
the  obferved  diredion  of  the  liars  on  the  wall,  the  moveable  wire  may  be  fet  to 
the  parallel  of  the  large  ftar,  which  will  give  the  angle  of  pofition  pretty 
accurately, 

f  See  note  to  IV.  5r» 

Vec^' 


of  Trouble  Stars.  6j 

II.  45.  Fl.  54  Vlrginls. 

April  3,      Double.     A   little  unequal.     Both  w.     With   227, 
1782.     il  or  near  i|  diameter,     Pofition  57"  o'  n.  follosvlng, 

46.  Fl.  42^"^  Comae  Berenices  fequens  ad  auftrum. 

April  15,  Double.  About  i|  degree  from  the  42d  Comer 
1782.  towards  v  Bootis ;  the  mofl  fouth  of  a  telefcopic  equi- 
lateral triangle.  Exceflively  unequal.  L.  pr.  ;  S.  d. 
With  278,  2  J  diameters  of  L. ;  not  fo  well  to  be  feeii 
\vith  higher  powers.  Pofition  6^  42^  f.  following.  A 
third  flar  preceding,  above  i  \ 

47.  Fl.  2  ComiE  Berenices. 

April  18,     Double.     Confiderably  unequal.      L.    rw. ;    S.    pr. 
1782.    With  278,   2  diameters  of  L ;  with  460,  above  3  dia- 
meters of  L.     Pofition  27°  42'  f.  preceding. 

48.  Prope  Fl.  16*'"  Auriga^. 

Aug.  28,  A  minute  double  ftar.  Lefs  than  |  degree  f  pre- 
1782.  ceding  the  i6th,  in  a  line  parallel  to  the  10  and  8 
Aurigas  ;  the  preceding  ftar  of  a  fmall  triangle  of  which 
the  1 6th  is  the  largeft  and  following.  A  little  unequal. 
Both  pr.  With  227,  i|  or,  when  heft,  i|  diameter 
of  L.     Pofition  15°  48^  n.  following. 

49.  0  (Fl.  iio*)Pifcium  borealior.     In  lino  boreo. 

Sept.  3,      Double.     About  I    degree  n.   of,  and  a  little  pre- 
1782.    ceding  iioth,   towards   vj  Pifcium.     A  little  unequal. 
Both  wr.     With  460,  about  3  diameters  of  L.     Pofi- 
tion 59°  6'  n.  preceding.     A  third  ftar  in  view,  about 
1 1  min. 

50.  Fl.  38.  Pifcium.     In  auftrino  lino. 

Sept.  4,      Double.     Pretty    unequal.      Both    pr.     With   227, 
1782.    full  2  diameters  of  L. ;  with  460,  about  4  diameters- 
of  L.     Pofition  25"^  3^  f.  preceding, 

K  2  51. 


68  Mr\  H£R9Cbel's  Catalogue 

II.  51.  p  Caprlcorni.  Fi  .  11.     Triuin  in  roflro  fequens. 
Sept.  5,       Double.     Very  unequal*     Both  rw.     With  460,   l| 
1782.    diameter  of  L.     Pofition  84°  o'  f.  following.     A   thicd 
ilar  in  view. 

52.  0  (Fl.  40'"')  Perfei  pr^xedens  ad  boream. 

Sept.  7,      Double.     Almoft  |    degree  preceding  the  40th,  in  a 
1782.    line  parallel  to  ^  and  the  38th  Perfei.     Equal.     Both  w. 
With  227,  nearly  2  diameters.     Pofition  8''  24'  n.  pre- 
ceding. 

53.  Fl.  12*'"  Camelopardali  praecedens. 

Sept.  7,  Double.  Lefs  than  \  degree  preceding  the  i  ith  and 
1782.  I2th,  in  a  line  from  the  ift  Lyncis  continued  through 
the  1 2th  Camelopardali.  Extremely  unequal.  Both 
dr.  With  227,  it  appears  like  a  ftar  with  a  tail;  but 
932  fhews  it  plainly  to  be  only  a  double  ftar ;  with 
227,  not  much  above  i  diameter  of  L. ;  with  932, 
H  ;        about  3 1  diameter  of  L.     Pofition  18°  ^'^^  f.  following  ; 

a  little  inaccurate. 
fj4.  Qua3  praecedit  &  (Fl  74*'",  oculum  boreum)  Tauri. 
Sept.  7,      Doubk.     Near  i    degree  f.    preceding  e,  in   a    line 
1782.    parallel   to  a   and  y  Tauri;  a  fmall  flar.     Extremely 
unequal.     L.  rw.  ;  S.  d.     With  460,  above  3  diameters. 
of  L.     Pofition  68°  42^  f.  preceding. 

55.  Fl.  4^  Ceti  auftralior  et  fequens. 

Sept.  9,      Double.     About   i    degree   f.    following  the  4th  and 
1782.     5th  in  a  line  parallel  to  oj  and  r  Ceti ;  in  the  fhorter  leg 

of  a   redangular  triangle.     Very  unequal.     L.  r. ;  S. 

d.     With  278,  rather  more  than   2  diameters.     PofW 

tion  21°  42'  n.  preceding. 

56.  /3  (Fl.  6*"")  Arietis  priEcedens  ad  boream. 

7  Double 


of  Double  Sl<r.rs.  69 

II.  Double.     Almofl:    i    degree   n.   preceding  fo    Arletis, 

Sept.  10,  towards  f  Andromcdac ;   a  fmall  ftar.     A  litrle  unequal. 

17S2.    Both  reddifh.     With  227,  full  2  diameters  ot  L.     Puli- 

tion  23''  1 2'  n.  preceding.  A  ."bird  flar  r/  or  7,'  preceding, 

in  the  lame  diredion  with  the  two  flars  of  the  double  ftar. 

57.  Ad  Fl.  72""  Aquarii. 

Sept.  27,    Treble.  About  2|  degrees  following  ;c,  in  a  line  parallel 

1782.    to  ot  and  71  Aquarii.     The  nearefl:  a  little  unequal.     Both 

r.     With  460,   2\  diameters  of  L.     Pofition  25°  51^  f. 

preceding.     The  two  fartheft  a  little  unequal.     Of  the 

5th  clafs.     About  50°  or  55°  f.  following. 

58.  Fl.  56^Ceti  auflralior  et  fequens. 

Sept.  27,      Double.     About  |  degree  f.  following  the  56th,  In  a 
1782.    hne  parallel  to  ^   and    t  Ceti.     Confiderably   unequal. 
Both  dw.     W^ith    278,   i{    diameter  of    L.     Pofition 
25°  12'  n.  preceding;   too  low  for  accuracy. 

50.  0  (Fl.  46*"')  Aquarii  fequens  adaullrum. 

Sept.  3c,       Double.     About  2  degrees  f.  following^,  in  a  line  pa- 

1782.    rallel  to  /9  and  I  Aquarii ;  there  is  a  very  confiderable  il:ar 

between  this  and  ^,  not  much  out  of  the  line.     Pretty 

unequal.     Both  dr.     With  227,   2j  or  2$  diameter  of 

L.     Pofition  61°  12'  n.  preceding. 

60.  £  (Fl.  5*"")  Canis  majoris  fequens  ad  boream. 

Sept.  30,     Double.     About  \  degree  n.  following  the  2d  ad  |, 

1782.    in   a   line  from   the   4th  continued   through    the    5th 

Canis  majoris  nearly.     Very  unequal.     L.  rw.  ;  f.   d. 

With  227,  1 1  diameter.     Pofition  67°  36'  n.  preceding. 

61.  TO-  (Fl.  47^"")  Orionis  fequens  ad  auftrum. 

oa.  2,       Treble.     About   ij|   degree  f.  following  tat  In  a  line 

1782.    parallel  to  (p  and  «  Orionis  ;  the  fmalleft  and  moft  fouth 

of  three  forming  an  arch.     The  two  nearefl  extremely 

unequal. 


T5  Mr,  Hersciiel^s  Catalome 

jI.  Dneqiuil.     L.  dw. ;  S.  a  mere  point.     With  227,   1 1  or 

1 1  diameter  of  L.  Pofition  4°  54'  n,  following  ;  too 
obfcure  for  accuracy.  The  two  fartheil:  extremely  inie- 
qual.  S.  a  mere  point.  Of  the  fourth  clafs.  Pofi- 
tion about  50  "■  f.  following. 

62.  Fl.  3^  Pegaii  adje£la. 

oa.  4,       Double.     In  a  line  with,  and  north  of,  the  two  flars 
1782.    that  are  about  the  place  of  the  third  Pegafi.     A  little 
unequal.     Both  dufky    r.     With    227,    about    3   dia- 
meters of  S.     Pofition  88*^  24'  n.  preceding;  perhaps  a 
little  inaccurate. 

63.  Fl.  3*"'  et  4^™  Navis  prsecedens. 

oa.  12,  Multiple.  Near  2  degrees  preceding  the  2d  and  4th 
J782.  Navis;  the  middle  one  of  three.  One  of  the  multiple 
is  double.  Nearly  equal.  Both  w.  or  afh  colour. 
With  227,  about  ^\  diameter,  and  not  lefs  than  20 
ftars  more  in  view ;  with  460,  about  3  diameters.  Po- 
fition 30°  12^  n.  preceding, 

64.  g  (Fl.  81*"")  Geminorum  ad  auflrum  fequltur. 

oa.  13,     Double.     About  \  degree  f.  following^,  in  a  line  from 

1782.    f  continued  through^  Geminorum  nearly;  the  neareft 

and   largeft  of  two.     Very  unequal.     L.  r.  ;  S.  bluifh 

r.     With   227,    above    3    diameters   of    L,     Pofition 

4°  9''  n.  preceding. 

65.  Pollucemfequens  ad  boream. 

Oci:.  13,  Double.  Full  |  degree  n.  following  /3,  in  a  line  from 
1^82.  ^  continued  through  /3  Geminorum;  the  ftar  next  to 
the  middle  one  of  three,  nearly  in  a  line.  Exceflively 
unequal.  L.  rw. ;  S.  d.  With  227,  above  2I  or  near 
3  diameters  of  L.  and  5  other  ftars  in  view  ;  with  460, 
above  3  diameters  of  L.  Pofition  89°  \z'  n,  following. 
^  1  66, 


of  Double  St^rs*  rt 

II.  (i(^,  Juxta  y  Delphini. 

Ocl.  19,       Double.     Full   |    degree  f.  preceding  y,  towards  ^ 

3782.    Delphini.     Confiderably  unequal.     L.  pr.  ;  S.  r.  With 

227,   il  diameter  of  L.     Pofition  78''  4.2^  n.  preceding.. 

67.  /G  (Fl.  10'™)  Lyras  praecedens  ad  boream. 

Oft.  19,     Double.     The  4th  telefcopic  flar  about  if  degree  n. 

1782.  preceding  /S,  in  a  line  parallel  to  y  and  cc  Lyras,  Ex- 
tremely unequal.  L.  r.  ;  S.  dr.  With  227,  i\  or 
almofl  1 1  diameter  of  L.  With  460,  above  z-  diame- 
ters of  L.     Pofition  68°  6'  f.  following. 

68.  Proxime  ^  Lyrae. 

oa.  24,  Treble.  About  2|  minutes  f.  following  ^  Lyras. 
1782.  The  two  neareft,  a  httle  unequal.  Both  dr.  With 
460,  3  full  diameters.  Pofition  8°  24'  n.  following. 
The  fartheft  as  large  as  L.  of  the  two  neareft  at  leaflu 
Colour  dr.  Pofition  with  L.  25°  57'  f.  preceding.. 
Diftance  of  ^  Lyrae,  which  is  in  view,  from  the  two 
neareft  2I  ly"  ^o''\  Pofition  6^""  12',  ^  being  n.  pre- 
ceding, or  the  double  ftar  f.  following. 
^9.  Fl.  4^""  Cygni  fequens  ad  boream. 

oa.  24,     Double.     Near  |  degree  n.  following  the  4th  Cygni, 

1782.    ifi   a  line  from  y  Lyrse   continued  through  the    4th 

Cygni.     A  little  unequal.     Both  w.     With  227,  about 

2  diameters  of  L.  or  2|  when  beft.     Pofition  29°  12' 

n.  following. 

70.  rm  8    telefcopicarum   %  (Fl.    15.)   SaglttiE   fequentium,  , 

ultima. 
Nov.  6,      Double.     About  1 1  degree  f.  following  %  Sagitt^,  in 
J 7 82.    a  line  parallel  to  y  Sagittse  and  y  Delphini.     Extremely 
unequal,    Both  r, ;  S.  deepei:  r.    With  227,  i|  dia- 
meter 


72  Mr,  Herschel's  Catalogue 

\[,         meter  of  L.  ;  with  460,  above  2  diameters  of  L.    Po- 
fition  nz'  57'  n.  following. 

7  I .  Fl.  58'  Aurigae  auftralior. 

Nov,  6,  Multiple.  About  |  degree  f.  of  the  58th  Aurigae,  in 
1782.  a  line  parallel  to  /3  and  Q.  A  clufter  of  ftars  containing 
a  double  ftar  of  the  fecond,  and  one  of  the  third  clafs. 
That  of  the  fecond  very  unequal.  Both  r.  With 
460,  about  2 1  diameter  of  L.  Pofition  44°  36'  n. 
following ;  that  of  the  third  equal.  Both  r.  With 
227,  above  20  ftars  in  view.  Diftance  ly"  41'^'.  The 
two  double  ftars  are  in  the  following  iide  of  a  fmair 
telefcopic  trapezium. 

72.  Fl.  13^  Lyncis  auftralior. 

Nov.  13,     A  pretty  double  ftar.     About  i|  degree  f.  of  the  13th 
1782.    Lyncis,    towards  Q  Geminorum ;    a  conliderable   ftar. 
Nearly  equal.     Both  pr.  With  227,     full  2 1  diameters; 
with  460,  almoft  4  diameters.     Pofition  11°  o'  f.  pre- 
ceding. 

73.  Fl.  21*  Urfae  majoris. 

Nov.  17,     Double.     Very  unequal.     Both  rw.     With  227,  zl 
17S2.    diameter  of  L. ;  with  460,  above  3.     Pofition  36°  45' 
n,  preceding. 

74.  V  (Fl,  4*)Crateris  borealior. 

Nov.  20,  Treble.  Near  i  degree  n.  preceding  v  Crateris, 
1782.  towards  a,  Leonis.  The  two  neareft  equal.  Both  dw. 
With  227,  2i  or  3  diameters.  Pofition  71°  ^'^'  n.  fol- 
lowing. The  fartheft  larger  than  either  of  the  two 
other  ftars.  Of  the  fixth  clafs.  Pofition  about  68  or 
69°  f.  preceding  the  double  flar. 


cf  Doubk  Stars,  jrj 

II.  75.  Fl.  1 18  Tauri. 

Dec.  7,  Double.  A  little  unequal.  L.  vv.  ;  S.  w.  Incrming; 
1782.  tor.  With  278,  2.1  diameter  of  L. ;  with  the  fame 
power  by  the  micrometer  j^"  41'^^;  more  exai^lly  with 
625,  5''  2' ^  Polition  77"  15'.  I  could  jull;  fee  it 
with  ail  18-inch  achromatic,  made  by  Mr.  Nairne;  it 
was  as  clofe  as  poffible,  and  a  pretty  objeft. 

76.  T  (Fl.  6'^^)  Arietis  auftralior  etpr^cedens. 

Dec.  23.     Double.     About     i     degree    f.    preceding   r    Arietis, 

1782.    towards  ^  Ceti ;  the  mofl:  fouth  of  two  fmall  teiefcopic 

ftars.     Nearly   equal.     Both  w.     With   227,  above  3 

diameters;  by  the  mici-ometer  ^"  ^"^"'^     Pofition  15'' 

24'  f.  preceding. 

77.  *Fl.  17  Hydrse. 

Dec.  28,     Double.      The  largeft   of  two.      A  little  unequal. 

1782.  Both  w.     With  227,   2 1  diameter  of  L, ;  with  460,  i| 
diameter.     Pofition  90°  o'  north. 

78.  ;^  (Fl.  63""')  Leonis  fequens  ad  auftrum. 

Jan.  I,       Double.     About  f  degree  f.  following  ;:^/,  towards  r 

1783.  Leonis;  the  fmalleft  of  two.  Very  or  extremely  un- 
equal. L.  r. ;  S.  d.  With  227,  3  full  diameters  of 
Lr.     Poiition  75°  21'  f.  following. 

7p,  Fl.  39  Bootis. 

Jan.  8,       A  pretty  double  jftar.     A  little  unequal.     Both  pr. 
1783.    With  227,  near  i|  diameter  of  L. ;  wnth  460,  near  2 

diameters  of  L.     Pofition  38°  21'  11.  following. 
80.  d  (Fl.  40*)  Eridani  adjeda. 

Jan.  31,     Double.      About   if   min.   f.   following  d  Eridani. 
1783.    Very  unequal.     Both  dr.     With  227,  hardly  vifible ; 
with  460,  very  obfcure.     Pofition  56°  42'  n.  preceding. 
Vol.  LXXV.  L  *  Diftance 


74  ^^'  Herschel's  Catalogue 

II.  Diftance  of  L.  from  ^Eridani,  with  227,  i'  2i^'47^''» 

Pofition  of  L.  17°  53^  f.  foliowlng  c/'Eridaiii. 
81.  Fl.  49^""  Eridani  fequens. 

Jan.  31,      Double.      Near  i  degree  following  the  49th  Eridani^ 
J 783.    towards  I  Orionls.     Very  unequal.     Both  dw.     With 
227,  full   I    diameter  of  L. ;   with  278,    1 1  or    i|   dia- 
meter of  L.  ;  with  460,   2.1  or.3  diameters  of  L.     Po- 
lition  51°  36'  n.  preceding, 
82:  Fl.  31^""  Bootis  fequens  ad  auftrum. 

Feb.  3,       Double.     Near  i   degree  f,  following  the  31  ft,  in  a 
1783.    line  from  v  continued  through  the  3 1  ft  Bootis  ;  the  moft 
fouthoftwo.     A  little  unequal.     L.  w. ;  S.  dw.    With. 
227,  about  1 1  diameter  of  L. ;  with  460,  about  3  dia- 
meters of  L.     Pofition  1  °  o^  f.  following.     A  third  flat 
,!  ,   ,    .  in  view,   20°  or  30°  n.  preceding. 

83.  Fl.  22^  Andromedse  boreaiior. 

Feb.  26,     Double.     Within  |    degree  north  of  the  2 2d,  in  a 
1783.    line  parallel  to  the  19th  and  i6th  Andromedae;  the  fol- 
lowing and  fmallefl:  of  two.  Confiderably  unequal.  L.w.; 
S.  d.     With  227,   lior  if  diameter, of  L. ;  with  460, 
more  than  2  diameters  of  L.  Pofition  5°  48^11.  following. 

84.  Fl.  65  Pifcium.    , 

Feb.  27,     Double.     Nearly  equal.     Both  pr.     With  227,  near 
1783.     i  I  diameter  of  L. ;,  with  460,  full  2  diameters.     Pofi- 
tion 30°  q7^n.  preceding. 

85.  b  (Fl..  36'')  Serpentis  boreaiior  et  fequens. 

Mar.  4,      Double.     About  I  i  degree  n.  following  ^,  nearly  in 
1783.    a  line  from  the  3 2d  continued  through  the  36th  Ser- 
pentis.    Extremely  unequal.     L.  w.  ;    S.  dw.     With 
227,   I  full  diameter  of  L. ;  S.  hardly  to  be  feen  ;  with 
460,  full  2  diameters  of  L.    Pofition  46°  9'  n.  preceding, 

86. 


tf  Double  Stars,  75 

IT.  86.  Fl.  49"™  Serpentis  praecedcns  ad  auftrum. 

Many-,-     Double.     About  1 1  degree  f.  preceding  the  49tli,  in 

3.78'^.    a  line  with  the  49th  atid  another  between  this  and  the 

49th  Serpentis,  each  nearly  at  |- degree  diflance.     Very 

unequal.     L.  dw.  ;  S,  d.     With  227,   2  diameters,  or 

2|  when  beft.  '  Poiition  ^^"^  9^  f.  following. 

87.  F-L.  29^et30^  Monocerotis  anftralior. 

Mar.  8,  Multiple.  It  makes  nearly  an  equilateral  triangl^i 
j_8o.  with  the  29th  and  30th  Monocerotis  towards  the  fouth. 
Among  many,  the  fourth  from  the  fouth  end-  of  an 
irregular  long  row  is  double.  A  little  unequal.  Both 
pr.  With  22p,  1  diameter  of  L.  and  16  more  in 
view.     Pofition86''  12'  f.  following. 

88.  0}  (Fl.  5t'"^)  Serpentis  prscedens  ad  auftrum. 

MaT.  8,       Double.     About    i    degree'   f.    preceding  the    5ifl:, 
'1783.    towards  the    13th  Serpentis,-    Very  or  extremely  une- 
qual.    Both  r.     With  1227,  zl  diameter  of  L.   when 
beft;    with  46b,   .near '3.  diameters    of   L.      Pofition 
44°  45'  n.  preceding. 

89.  Ad  Genam  Monocerotis. 

Mar.  26,     Double.     About  i  degree  n.  preceding  the  1 2th  Mo- 

-1783.  •  nocerotis,  in  a  line  parallel  to  «  and  x  Orionis ;  the 
fmallefl  and  moil  liorth  of  two.  Coniiderably  une- 
qual. L.  r.  ;  S.  bluifh'  r.  With  227,  near  4  diame- 
ters of  L.  when  befl.     Pofition  50°  51^  n.  following. 

00.  Fl.  ioo^"*  Herculis  prsecedens  ad  boream. 

Mar.  27,     Double.     About  i|   degree  n.   preceding  the  looth, 

1783.    towards  jtt.  Herculis ;  a  very  fmall  telefcopic  ftar;  the 

moft  towards  ^a,  and  fmalleft  of  three  forming  an  arch. 

Coniiderably   unequal.     Both   dw.     With  227,  about 

2  .diameters  of  L.     Pofition  75*^  9^  f.  foliovving* 

L  3  91. 


/ 


76  Mr.  Hkrschel's  Catalogue  \ 

II.  91.  %  (Fl.  15^)  Sagittic  auftralior. 

Apr.  5,  Treble.  About  twice  as  far  ibutii  of  %  Sagitta%  as  % 
J 783.  and  the  ftar  near  it  are  from  each  other;  a  fmall  ftar. 
The  two  nearefh  very  unequal.  L.  pr. ;  S.  r.  With 
227,  \i  diameter  of  J^.  Pofition  74.'^  54'  f.  preceding. 
The  third  with  L.  extremely  unequal.  S.  d.  With 
227,  about  3  diameters  of  L.  or  more.  Pofition  about 
40°  or  50^  n.  preceding.  With  more  light  this  would 
be  a  fine  objed:. 
92.  In  Camelopardali  clune. 

Apr.  30,  Double.  About  four  times  the  diftance  of  the  loth 
1783.  and  1 2th  Camelopardali,  north  of  the  loth,  and  almofh 
in  the  fam.e  diredlion  with  the  loth  and  12th,  is  a  ftar 
of  between  the  5th  and  6th  magnitude  not  marked  hi 
Flamsteed  ;  naming  that  ftar  A,  we  have  the  fol- 
lowing direction.  About  |  degree  preceding  A  Came- 
lopardali, in  a  line  from  the  2d  L-yncis  continued 
through  A  ;  the  fecond  from  A.  Very  unequal.  L. 
w. ;  S.  dv  With  227,  if  or  2  diameters  of  L.  Po- 
fition 22°  42'  f.  following.  Very  inaccurate. 
^^,  B  (Fl.  13^)  Aquilae  auftralior. 

May  25,     Double.     Near   |   degree  fouth  of>  and  a  little  fol- 
1783.    lowing  f,  towards  A  Aquilae,  a  very  fmall  ftar.     Verj- 
unequal.     L.   dw. ;  S.   dr.     With  460,  above   2  dia- 
meters of  L.     Pofition  16"  o''  n.  preceding. 
^4.  I  (Fl.  17*"")  Andromeda^  pra'cedens  ad  boream. 
Aug.  19,     Double,    About  if  degree  n.  preceding i  Andromedas 
1783.    in  a  line  parallel  to  a  and  jG  Caffiopeias ;  in  the  fide  of  a 
trapezium  of  four  fmall  flars.     Pretty  unequal.     Both 
r.     With  460,  2i  diameters  of  L.     Pofition  54°  24' 
n.  preceding. 

95' 


of  Double  Stars,  77 

II.  95.  fi  (Fl.  k,^^^  Aquilse  auftralior. 

Sept.  12,      Double.     About  \  degree  loutli  of  ^,  in  a  line  from 

178^.    o-.  continued   througb  y\  Aquilas ;  a  fmall  ftar.     A  little 

unequal.      Both  dulky  afli-coloured.     With   460,  near 

3  diameters  of  L. ;  with  278,  near  2   diameters  of  L. 

Pofition  29°  2!  '^'  preceding. 

96.  ^  (Fl.  65^)  x'\quilas  borealior  et  fequens. 

Sept.  i2»     Double.     About    i|    degree  n.  following^  Aqu/iki.^ 
1783.    towards  6  Delphini ;  more  accurate  towards  29  Vulpe- 
culae ;  a  very  conflderable  ftar.     Nearly  equal.     Botli  ■ 
rw.     With  278,  about  \\  diameter  of  L.  ;  with  460^  , 
full  2  diameters.     Pofition  56°  I2^f.  preceding. 

97.  f  (Fl.  64^"")  Cygni  praecedens. 

Sept.  15,     Treble.     About   i    degree  preceding  f,  towards  the 
•*7?3*    41ft  Cygni;  a  large  ftar.     The  two  neareft  extremely 

unequal.     L.   w.  ;  S.  pr.     With  460,  2f  diameter^  Qf  / 

Xv,     Pofition  45°  15'  n.  preceding.     The  third  with  L. 

extremely  unequal.     Of  the  5th  or  6th  clafsr;  about  : 

50°  f.  preceding. 

98.  Fl.  49  Cygni. 

Sept.  15,     Double.     Very  unequal.     L.  r. ;  S.  bluJfh  r.    With 
1783.    278,   If   diameter  of  L.  ;  with  460,  ^\  diameters  of  r 
L.     Pofition  31^48^  n.  following. 

99.  /S  (Fl.  6*'")  Cygni  fequens  adboi'eam* 

Sept.  15,     Double.     Near  |  degree  n.  following  /?,  towards  | 
1783.    Cygni.     Very  unequal.      Both   dw.     With   278,    i| 

diameter  of  L. ;   with  460,  about  z  diameters  of  Lo  . 

Pofition  87°  48'  n.  following. 

100.  Fl.  51^  Cygni  boreallor  et  fequens. 

Sept.  24,     Double.     Near  two  degrees  n.    following  the   51ft  ^ 
1783.    Cygni,  in  a  line  parallel  to  0  Cygni  and  a  Cephei ;  a 


yS  Mr.  Herschel's  Catalogue 

II.  pretty  confiderable   ftar.     Very   unequal.     L.  w. ;  S. 

inclining  to'  blue.  With  278,  extremely  unequal, 
and  I  i'diarrieters'  of  L;  when  bed  ;  requires  attention  to 
be  feen  wellwith  this  power ;  with  460,  full  2  diame- 
ters of  L.  or  2|'  when  beft,-  otherwife  much  lefs.  Poli- 
tion  15°  5i''n.  following.   '  - 

10 1.  Fl.  57^"*  ::  Canielopardali  prsecedens  ad  boream. 

Sept.  26,  Double.  About  2  degrees  n.  preceding'  the  57  :: , 
•1783.  towards  the  42d  Cameloipardali ;  a '  eoiifiderable.,ftfir 
near  three  fmaller,  forming  an  arch.  About 'i  degree 
from  the  double  ftar  V.  135.  Conliderably  unequal. 
Both  pr.  V/ith  278,  if  diameter  of  L.  ;  with  460, 
2|  diameters  of  L.     Pofition  67°  15' ni, preceding. 

102.  e  (Fl.  29^)  Orionis  auftralio^r  et  pr^ecedens. 

Sept. 27,     Double.     About   |   degree   f.  precediug  ^,  in  aline 

J783..  parallel' to  ^  and  jG  Orionis ;  the  krgeft  o^  feveral.   Very 

*    ''*  .unequal.     L.  pr.  ;  S.  inclining  to  garnet.  '  With  278, 

inear  2  diameters  of  L.     With  460,  2 1   diameters  of 

L.     Pofition  52°  24^  f.  following. 


.1;  •;  :1rh-;'- 

THIRD     CLASS      0  F  '  b  QUEL  £     ST  A  R  S. 

III.  47.  e  Pollucis;     Fl.  38  Geminorum.     In  cake.  . 
Dec.  27,     Double^    Extremely- unequal.     L.  rw* ;  S.  r.     Dif- 
1781.    tance,  with  460,  7;^i48''^     Pofition .89°  54^  f.  follow- 
ing.    Two  more  in  view,  the  nearefl  of  them  perhaps 

40'^ ;  thev  form  a  redan gle  nearly. 
.     ;  •  '  ,  48. 


'  of  Double  Stjrs.  ■  .yt^ 

ni.   43.  ;•  (Fii.  61''"')  Gemlnorum  piaDcedcns  ad  boream.' 
Dec.  27,,     Double.     About  i   degree  n.   preceding  r,  in   a  line 
J ''Si.    parallel  to  a  and  the  60th  Geminorum  ;   near  two   de- 
grees from  ^.     A  little  unequal.     Both  pr.     Dirtance 
^//  i^'^\     Pofition  43"^  54^  n.  following. 

49.  ^  (Fl.  4'")  Hydri£  priccedens  ad  boream. 

Jan.  20,      Double.     About  1 1  degree  n.  preceding  ^,  in  a  line 
1782.    from  71  continued  through  ^  PIydri£.     Pretty  unequal. 

L.   r.  ;    S.  garnet.     Diftance   12''   30^^^     Pofition  62*^ 

48'  n.  following. 

50.  5  Virginis.  Fl.  51.     De  quatuor  ultima  et  fequens. 

Feb.  6,       Treble.    The  two  nearefl  extremely  unequal.    L.  w. ; 
1782.    S.  d.     Diftance  7^^  8^^^ ;  but  inaccurate  on  account  of 

the    obfcurity  of  S.     Pofition   69°    iS'    n.    preceding. 

For  meafures  of  the  two  fartheft  fee  VI.  43. 

51.  Fl.  88  Leonis.     In  dextro  clune. 

Feb.  g,       Double.     Extremely  unequal.     L.  rw.  ;  S.  r.     Dif- 
1782.    tance   14^^38^^^;  a  little  inaccurate.     Pofition. 47°  33' 
n.  preceding. 

52.  Fl.  lo^'"  Orionis  fequens. 

Feb.  17,     Double.    Above  i  deg.  n.  following  the  loth,  towards 
1782.    w  Orionis.     Confiderably  unequal.    Both  pr.     Diflance^ 

with  278,   13'^  40'^^     Pofition  37°  3^  n.  follov/ing. 
53'  y  Virginis  borealior  et  fequens. 

Feb.  17,     Double.     Near.  2 1  degrees  n.  following  <)/,  in  aline 

1782.    parallel  to  s  and  a.  Virginis ;  a  conliderable  f!:ar;  a  line 

from  y  to  this  pafles  between  two  of  nearly  the  fame 

magnitude  with  this  ftar.     A  little  unequal.     Both  d, 

Diflance  12'^  58'^^     Pofition  79°  o'  n.  preceding. 

2  54* 


^&-  Mr.  Herschel*s  Catalogue 

III.  54.  SecunJa  ado-  Urfs  majoris.     Fl.  13,     la  fronte. 
June  2,       Double.     Extremely  unequal.     L,   w. ;   S.   r.     Dif- 
1782.    tance  j"  56''^''.     Poiition  i3°o'n.  preceding. 
^^.  V  (Fl.  18^"™)  Coronie  borealls  fequens  ad  boream. 
June  14,     Double.       Coniiderably    unequal.      L.     dr, ;    S.    d. 
1782.    Diftance  with  227,  about  3  or  4  diameters  of  L.  being 
too  obfcure   for  the  micrometer.     Pofition   ^tj'  4^'  ^• 
preceding.     Diftance  of  the  largeft  of  the  two  from  u 
Corons  i'  iW  %"\     Poiition  of  the  fame  with  u,  64"* 
24'  n.  following. 
:^6.  S  (Fl.  72^)  Serpentarii  borealior. 
June  16,     Double.     About  2f    degrees  n.  of  the  yad   Serpen- 
1782.    tarii ;  a  confiderable  fiar.     A  little  unequal.     Both  r. 
Diftance  7^' 3y'''.     Pofition  9°  42^  f.  preceding,   A  third 
ftar  about  1'  preceding, 
■^'j.  In  Anferis  corpore. 
Aug.  II,     A  pretty  double  flar.     About  |  degree  n.  of  a  clufter 
1782.    of  ilars  formed  by  the  4th,  5th,  7th,  9th  Anferis;  in 
a  line  parallel  tathe  6|:li  Vulpeculasand  /2  Cygnl ;  that 
of  two  which   is  farthefl:  from  the   clufler.     A   little 
unequal.     Both  r.     Diflance  Y'  i'^'.     Pofition  58°  36' 
f.  followino", 
■58.  6  Perfei.  Fl.  1.3.     In  finiflro  humero. 
Aug.  20,     Double.    Extremely  unequal.     L.  w.  inclining  to  r. ; 
1782.    S.  d.     Diftance  with  932,   13''  3^"'*     Pofition  2 o'' o' 
n.  preceding,     A  third  ilar,  very  unequal,  within  i' ; 
towards  the  foutii. 
'^(),  Ad  Fl.  i9''"Perfei.     In  capite. 

•  Aug.  20,     Doable.     It  is  perhaps  the  19th  Perfei  removed,  or 
.1782.    more  likely  a  fear  not  marked  in  Flamsteed's  Cata- 
logue ;  the  1 9th  being  either  vanilhed,  or  mifplaccd  by 

Flamsteed, 


of  Double  Stars*  S^ 

III.        Flamsteed.     Pretty  unequal.     L.  b\v. ;  S.  bi%     Dif-"' 
taiice  12^'  2^'^     Pofitlon  o"  o^  following. 

60.  Secunda  ad  /  Perfei.  Fl.  20.  Illas  in  larva  praecedlt.''^ '^''^ 
Aug.  20,  Double.  Extremely  unequal.  L.  rw. ;  S.  d.  DiC- 
1782.    tance  14''  1"'.     Pofition  30°  30'  f.  following. 

61.  Sub  finem  caudae  Draconls. 

Aug.  29,     Double.     Of  two  confiderable  flars,  about  half-way 

1782.    between   a,  and  i   Draconis,  that   which   is  towards  /. 

The   two  ftars  are  parallel  to  ^  and   e  Urfae  majoris. 

Very  unequal.     L.  pr. ;  S.    db.     Diilartce    12^^30^'^^ 

perhaps  a  little  inaccurate.   Pofition  87^  42'  n.  preceding. 

62.  Fl.  35  Pifcium.     In  lino  auftrino. 

Sept.  4,       Double.     Confiderably    unequal.      L.    rw. ;     S.    pr. 
1782.    Diflance  12'^  3^^''-     Pofition  58°  54^  f.  following. 

63.  Prope  Fl.  65*™  Saglttarii.     Ad  extremum  paludamentiim, 
Sept. 5,      Double.     Near  |  degree  f.  following  the  65th  Sagit- 
1782.    tarii  towards  ^  Capricorni.     Very  unequal.     Too  low 

for  colours;  perhaps  dw.     Diflance   14'^  20'''.     Poli- 
tion  73°  48'  n.  following. 

64.  Fl.  26  Aurigce.     In  dextri  cruris  irivolucro. 

Sept.  5,      Double.     Very  unequal.     L.  rw. ;    S.   r,     Diflance 
1782.     13  '  ^s"''     Pofition  2°  36^  n.  preceding. 

65.  e  (Fl.  58'")  Perfei  aufrralior.     In  dextri  pedis  talo. 

Sept.  7,      Double.     About  10'  fouth  of  the  58th  Perfei,  in   a 

1782.    line  parallel  to  f  and  i  Aurigas;  a  fmall  telefcopic  flan 

Very  unequal.     L.  r. ;  S.  d.     Diflance  with  625,   n'^ 

22''''.     Poiition  48°  54'  n.  following.     Very  inaccurate  t 

windy. 

66.  e  Tauri.  Fl.  30.     In  dextri  humeri  fcapula. 

Sept,  7,      Double.     Extremely  unequal.     L.  w. ;  S.  r.     Dif^ 
1782.    tance   11'^    \6"' \  inaccurate  on  account  of  obfcurity. 
Pofition  17°  15'  n.  following. 
Vol.  LXXV.  M  67. 


III.  67-.  ^  Leporis,  Fl.  3.  Borea  praecedentis  laterisqiiaclriiateri 

xid  aures. 
Sept.  7,      Double,     Exceffively  uneqijal.     L.  w. ;  S.  d.    With 
ij82,    327,  there  was  not  a  poffibillty  of  meafuriiig  the  dif- 
tance,  though  the  glafs  was  carefully  cleaned  ;  on  try- 
ing 625,  I  found  the  ftar  fo  ftrong  that  It   bore  a  very 
tolerable  good  light*.     Diftance  with  this  power  iz^^ 
zo'" .     Pofition  8v°  2.1'  n.  preceding. 
68.  y]  (Fl.  17*)  Arietjs  auftralior  et  praecedens. 
Sept.  10,     Double.     Full  I  degree  fouth  preceding  1;,  in  a  line 
J 782.    parallel   to   a  and  y   Arietis.      Very  unequal.     L.  pr. ;, 
S.  d.     Diftance  8''  ^"\     Politlon  SS""  4^'  1^-  following. 
^^.  Prope  Fl.  64""  Aquarii.     In  dextro  femore. 
Sept.  27,     Double.     Full   i|   degree  n.  following  the  64th  ::  , 
J 782.    in  a  line  parallel  to  \  and  (p  Aquarii ;  the  largeft  of  two 
that  follow  a  very  obfcure  triangle  in  the  hnder.     Ex- 
tremely unequal.     !>.  rw. ;  S.  db.     DIflance  12^' 4.6'''. 
Pofition  20°  3''  f.  following. 
70.  «  Cephei.  Fl.  i.     In  dextro  crure. 

Sept.  27,     A  beautiful    double  flar.     Extremely   unequal.     Lw 
1782.    fine  w.  ;  S.  r.     DIflance  5''  47''^.     Pofition  32°  30^  f.. 
following. 

*'  With  regard  to  fniall  ftars,  that  become  vifible  by  an  increafe  of  magnifyino' 
power,  w€  may  furmife,  that  it  is  partly  owing  to  the  greater  darknefs  of  the 
field  of  view,  arifing  from  the  increafed  power,  and  partly  to  the  real  efFeft  of- 
the  power,;  for,  though  the  real  diameter  of  a  ftar,  notwithilanding  it  be  magnified 
a  thoufand  times,  fliould  itill  remain  fmaller  than  the  minrmum  vifibile,  yet  fince  a 
Ibr  of  thefeventh  magnitude  maybe  feen  by  the  naked  eye,  we  may  conclude,  that 
the  light  of  a  ftar  fubtends  incomparr^bly  a  larger  angle  than  its  luminous  body ; 
and  this  may  be  in  fuch  a,  proportion,  with  very  fmall  flars,  that  the  power  of 
the  telefcope  fliall  be  juft  fuiFicient  to  magnify  the  real  diameter  fo  as  to  bring  it 
with  ill  the  limits  of  this  proportionj  wheteby  the  Har  will  become  vifible. 

7J- 


of  Dotible  Stars,  8f  ? 


3 

111.  71.  Tiaram  Cephel  prjEcedens. 

Sept.  27,      Treble.     About  1 1  degree  preceding  the  game ij^ar  *\, 
1-82.    ill  ^  li"s  parallel  to  i  and  ^Cephei.     The  two  nearefi: 


very  unequal.     ly.    w. ;    S.   db.     Diftance    11  '     -»;:■ 


^'    or/'/ 


Politlon  35°  24'  f.  following.  The  two  farthefl  conf).- 
derably  unequal.  S.  db.  Dulance  iS'^  37^^^-  Pofi- 
tion  y^°  ^Y  II.  preceding.  The  place  of  \\\t garnet 
jiar^  reduced  to  the  time  of  Flamsteed's  Catalogue,  is 
about  7R  21  h.  45'.     P.D.  32°!. 

72.  Tiaram  Cephei  pr^ecedens. 

Sept.  27,     Double.     Within  |  degree  of  the  foregoing  treble 
1782.    ftar.     Confiderably  unequal.     L.  rw. ;  S.  pr.    Dlflance 
13^^  7^^^.    Pofition  32°  o^  n.  following. 

73.  Fl.  25^  Ceti  auftralior  et  fequens. 

Oft.  2,       Double.     About  |  degree  f.  following  the  25th,  in  a 
1782.    line  parallel  to  ^  and  r  Cetl.     Pretty  unequal.     Diftance 

with  278,   \^'   50^"^     Politlon   89^12'  f.  preceding; 

perhaps  a  little  inaccurate. 

74.  Fl.  18^  Pegafi  auftralior.     Ad  oculum  finlftrum. 

Oft.  4,       Double.     About  |  degree  f.  preceding  the  18,  in  a 
1782.    line  parallel  to  f\  and  e  Pegafi ;  the  moft  north  and  largeft 
of  two.     A  little  unequal.     Both   rvv.     Diftance  14" 
^()'"  full  meafure.     Pofition  31^  2>o   ^i*  following. 
75»  Ad  Genam  Monocerotis. 

Oft.  4,       Double.     About  1  degree  n.  of,  and  a  little  preceding 
1782.    the  fix  telefcopics  in  the  place   of  the  12th,  in  aline 

parallel  to  the  1 2th  Monocerotis  and  ^  Gemlnorum. 
76*  rm  quatuor  tclefcopicarum,^  Ononis  fequentium,  penultima. 
Oft.  4,       Double.     About   |  degree  n.  following  J",  in  a  line 
1782.    parallel    to   t    and   i   Ononis.      Extremely    unequal. 

*  Phil.  Tranf.vol.LXXIII.  p.  257. 

M  2  L. 


84  -^^'  Herschel's  Catalogue 

III,        L.   r. ;  S,  d.     Diftance  with  278,  9^'    12^'\     Polition 
13°  6'  n.  preceding. 

77.  Fl.  65"""  Arietis  feqiiens  adauftrum. 

oa.  9,       Double.     About  I  degree  f.  following  the  65th  Arie- 
1782.    tis,  in   a  line  parallel  to  the  Pleiades  and  e  Taurl ;  the 

preceding  of  two.     Very   unequal     L.  r. ;  S.  bluifh. 

Diflance  8'^  32''^     Pofition  yf  18'  f.  following. 

78.  Fl.  13^""  Tauri  prascedens  ad  auftrum. 

06V.  9,       Double.     About    i|    degree    f.    preceding   the    13th 
1782.    Tauri,  in  a  line  parallel  to  £  Tauri  and  I  Ceti.     Nearly 

equal.     Both  pr.     Diflance  7^'  10'''.     Pofition  87°  57' 

n.  preceding. 

79.  e  (Fl.  83^)  Ceti  borealior. 

oa.  13,     Double.     About  f  degree  n.  of  e  Ceti ;  the  neareH:  of 
1782.    three  forming  an  arch.     Extremely  unequal.     L.  rw. ; 
S.  darkiih  red.     Diftance  with  278,   10''  48^'^     Pofi- 
tion 45°  1 2^  f.  preceding. 

80.  <r  (Fl.  76'"*)  Ceti  prsecedens.     In  finiftro  crura. 

oa.  13,     Double.     Full  i|  degree  preceding  0-,  towards  t  Ceti. 
1782.    Extremely  unequal.     L.  rw. ;    S.   br.     Diftance    11^^ 
16^^^.     Pofition  22°  24^  n.  preceding. 

81.  Parvula  a  ^Lyrae  g  verfus. 

oa.  19,     Double.     Above  I  degree  from  ^  towards  g  Lyras. 
1782.    Extremely  unequal.     L.  r. ;  S.  dr.     Diflance  9^'  27^^' 
full  meafure.     Pofition  66°  18^  n.  following* 

82.  Fl.  41  Aurigae. 

Nov.  6,      A  pretty  double  flar.     Confiderably  unequal.     L.  w. ; 
1782.    S.  grey  inclining  to  r.     Diflance  8^^  32^^^.    Pofition   • 
80°  o'  n.  preceding, 

S3. 


cj  Doubk  Stars,  8  r 

III.  83.  Fl.  19  Lyncis. 

Nov.  13,     Double.     A  little   unequal.     L.  rw.  j   S.  b\v.     Dlf- 
1782.    tance  14''  1 1^^^     Polition  46°  54^  f.  preceding. 

84.  Fl.  40  Lyncis.     In  Urfae  majoris  pede. 

Nov.  13,     Double.     Very  or  extremely  unequal.     L.  wr. ;  S.  r. 
1782.    Diftance  Y'  ii'^^«     Pofition  48''  12'  n.  preceding. 

85.  Fl.  2  Canum  Venaticorum. 

Nov.  13,     Double.     Very   unequal.     L.    r. ;    S.    bluifh.     Dif- 
1782.    tance  12^^  12^^^     Pofition  1 1  °  o^  f.  preceding. 

86.  Fl.  57  Urfe  majoris. 

Nov.  20,     Double.     The  largeft  of  two  ftars.     Exceflively  un- 
1782.    equal.     L.  w. ;  S.  a  red  point  without  fenfible  magni- 
tude.    With  227,  S.  is  but  jufl  vifible,     Pofition  75^ 
36^  n.  following. 

87.  Fl.  59*  Urfae  majoris  borealior. 

Nov.  20,  A  pretty  treble  ftar.  Near  i|  degree  n.  of  the  59th, 
1J82.  hi  a  line  parallel  to  ^  and  /3  Urfae  majoris  nearly.  The 
two  neareft  confiderably  unequal.  L.  pr.  -,  S.  r.  Dif° 
tance  1 2^^  30'^^  Pofition  o""  o^  preceding.  The  two 
fartheft  very  unequal.  S.  dr.  Didance  32^^  21^'^j 
Pofition  4°  o^  n.  following. 

88.  Fl.  ii^  Taurl  borealior  et  fequens. 

Nov.  25,     Double.     About   i    degree   n.    following   the    nth 
1782.    Tauri,  towards  /  Aurigas.     Very  unequal.     L.  w. ;  S. 
.    .     pr.     Diftance  with  278,  13^^  37^^^     Pofition  89^  51^ 
n.  following. 

89.  Ad  63^*"  Herculis.     In  linea  per  ^  et  £  du<£la. 

Nov.  26,     Double.     About  4  degrees  from  ^  towards  s  Herculis, 
1782.    iiear  the  63d.     Very  unequal.     L.  r.  ;  S.  r.     Diftance 
J  ^//  ^^///^    Polition  47°  48^  n.  following. 


^6  Mr,  Herschel's  Catalogue 

III.   90.  Fl.  103^  Tauri  borealior. 

Nov.  29,     Double.     About  three  degrees  diredly  n.  of  the  103 
1782.    Tauri ;  the  largeft  of  three,  formhig  aa  obtufe  angle. 
Confiderably  unequal.     L.  r\v.  ;  S.  pr,     Diflance  wklt 
278,   13''  6'"''.     Pofitlon  64°  o^  n.  foUowmg. 
^i.  Fl.  62^  Arietis  borealior  et  fequens, 
Dec.  23,     Double.     Near  i  degree  n.   followhig  the  62d  Ari- 
1782.    etds,  towards  g  Perfei.     Nearly  equal.    Both  dvv.     Dif- 
tance  ii'^  17^^^;    not  very  accurate.     Pofitioii  12°  24' 
n.  preceding  or  f.  followuig. 
^2.  f  (Fl.  ^j"]^"^^  Cancri  prascedens  ad  boream. 
Dec.  28,     Double.     About  i  degree  n.  preceduig  |  Cancri,  in  a 
17 82.    line  parallel  to  e  Leonis  and  the  41  ft  Lyncls;  a  confi- 
derable   ftar.     A  little  unequal.     Both  rw.     Diftance 
8^^  50^^^     Pofition  6^°  12^  f.  preceding. 
9  J.  Fl.  1 17  Tauri. 

Dec.  31,     Double.     Almoft  equal.     Both   fvv.     Diftance   12'' 
1782.     12'^^     Pofition  53°  27''  f.  following. 
^4^     V  (Fl.  7»"^)  I^eporis  praecedens  ad  boream. 
Dec.  31,     Double.     About  1 1  degree  n,  preceding  V  Leporis,  in 
1782.    a  line  parallel  to  X  and  e   Orionis;  the   fecond  in  that 
line.     Equal.     Both  rw.     Diftance    11''   44^^^     Pofi- 
tion 4°  o'  f.  following  or  n.  preceding. 
-95.  V  (Fl.  48*"")  Eridani  praecedens  ad  auftrum. 
Jan.  2,       Double.     Near  J-  degree  f>  preceding  v,  in  a  line  from 
.1783.    the  51ft  continued  through  the  48th  Eridani.  Extremely 
unequal.     L.   rw. ;  S.   d.  and  hardly  to  be  feen  with 
227.     Diftance   with  278,   15'^  21''';  very  inaccurate 
©n  account  of  obfcurity.     Pofition  9°  1 8^  f»  preceding. 

s  96. 


of  Double  Stars ^  %^j 

in.  96.  Fl.  lyCraterls. 

Jan.  10,     Double.      Nearly  equal.      Both    r\v.      Dllliance   ^'^ 
1783.    46^^^     Pofitlon  64''  zY  ^'  preceding. 

97.  Fl.  54  Hydrx. 

Jan.  10,     Double.     Very  unequal.     L.  w.  ;  S.  bluidi  r.    Dif- 
1783.    tance  i\"    \Y'^\   too  low  for  great  accuracy..     Pofitioti- 
^8°  1 5^  f.  following. 

98.  Ad  Genam  Monocerotis. 

Jan.  13,     Double.     About  f  degree  f.  preceding  the  mod.  f  of 
178,3.    a  clufter  of  fix  teleicopics  in  the  place  of  the  i  2th,  in  a 
line  parallel  to  the   15th  and    12th   Monocerotis.     Ex- 
eeflively  unequal,     Pofitlon  6  l°  57' f.  preceding.. 

99.  Fl.  ^'^^  Eridani. 

Jan.  31,     Doubk.     A   very   little  unequal.     L.   pr. ;    S,    rw.. 
1783.    Diftance  9'^  ()"\     Pofition  44^"  9^  n.  preceding. 
lOQ.  Fl.  ^i^^"^  Eridani  praccedens  ad  auflrum. 
Jan.  31,     Double.     About    z\  degrees:  f.  preceding  the   55th-. 
1783.    Eridani,  in  a  line  parallel  to  Rigel  and  y  Eridani.    Ccn- 

fiderably  unequal.     L.  pr.  ;  S.  db.     Diftance  i  \'^  S^"^' 

Pofitioa  16"  24^  f.  preceding. 

1 01.  ^  Centauri.  Fl.  3. 

Jan.  31,     Double.     Conliderably   unequal.     L.  d\v. ;    S.   dpr, 
1783.    Diftance  i  \"  SS'"'-     Pofition  22°  o^  f.  following. 

102.  h  (Fl.  29^"")  Herculis  praecedens  ad  auflrum. 

Feb.  3,       Double.     About   1 1    degree  f.  preceding  h  Herculis 
1-783.    towards  e  Serpentis ;  a  fmall  flar.     Very  unequal.    Both 
r,     Diftance  14^^  z^^\     Pofition  67°  i2^n.  following. 

103.  B  (Fl,.  37')  Serpentis  borealior  et  fequens. 

March  4,      Double.     Near  two  degrees  f  following  £,.  in  a  line 
^^83.    parallel  to    the    13th   Serpentis  and    10th   Serpentarii, 
Very  unequal.     L.  pr. ;  S,  r. ;  but  a  city  Jog,,  if  I  may 

fo 


S  ?  Mr ,  H  £  R  »c H  E  L* s  Calalog ue 

III.  To  call  It,  probably  tinges  them  too  deeply,  Diflance 
with  278,  12''  3V";  with  625,  iz"  23"^  Pofitioa 
50°  m'  Vi.  preceding. 

104.  Fl.  83^""  Herculis  prasccdens. 

JNiar.  26,      Double.     About   I   degree  preceding  the  83  ;  the  fe- 
1783.    cond   ftar  towards  the  79th  Herculis.     Very   unequal. 
L.  r. ;  S.  darker  n     Dlftance  14''^  2o''\     Pofition  83^ 
48^  n.  preceding. 

105.  y  (Fl.  12^)  Sagittje  borealior  et  prascedens. 

April  7,      Double.     About  2^  preceding  the  double  ftar  V.  106. 
1783.    Pretty    unequal.      L.   r. ;    S.   d.     Diftance    14^^29^^^; 

very   inaccurate,    on   account    of    obfcurity.     Pofition 

50°  24^  f.  preceding. 

106.  Fl.  5  Serpentis. 

May  21,      Double.     Excefiively  unequal.     L.  rw. ;  S.  db.  Too 
1783*    oblbure  for  mealures.     Of  the  third  clafs,  far.     Pofi- 
fition  about  30''  or  40^  n.  following. 

107.  Congerie  Stellularum  Sagittarii  borealior. 

June  6,       Double.     Above  i  \  degree  n.  of  the  20th  clufter  of 

•1783.    ftars   of  the  Connoijfance   des  l^emps,  in  a  line  parallel 

to  y  S'agittarii  and  the  clufler  :  the  moft  fouth  of  many, 

Confiderably  unequal.     Diftance  with  278,   15'^  lo^^^ 

As  accurate  as  the  prifmatic  power  of  the  atmofphere, 

which  lengthens  the  flars,  will  permit.     Pofition  54^ 

48''  f^  preceding*. 

108., 

*  What  1  call  the  prifmatic  power  of  the  atmofphere,  of  which  little  notice 
has  been  taken  by  allronomers,  is  that  part  of  its  refradive  quality  whereby  it 
ilifperfes  the  rays  of  light,  and  gives  a  lengthened  and  coloured  imqge  of  a  lucid 
point.  It  is  very  vifible  in  low  flaps;  Fomalhand,  for  inftance,  affords  a  beau- 
tiful prifmatic  fpedrum.  That  this  power  ought  not  to  be  overlooked  in  delicate 
4  and 


ef  I)sM$k  Starts       "  '■ 

III.   loS.  Fn.  r9»'»  Aqufepra^cedens  ad  boream* 
July  7,       Double.     Above  |  n.  preceding  the  iptli^  in  a  \m^ 
1783.    parallel  to  jG  and  f  Aquili£.     Very  unequal.     L.  r.  ;, 
^  S.  dr.     Diftance  12^'  58^"^     Pofition   58^  27''  f.  fol« 

lowing. 
109.  Fl.  19*"*  Aqurlas  priEcedens  ad  Boream» 
July  7,       Double.     About  ij  degree  11.  preceding  the  19th,  iur' 
1783.    aline  parallel  toe  and  ^i\quiliE.     Pretty  unequal.    Both 
rw.     Diftance  10^^  I3^^^»  •  Portion  22'^  6^  n.  preceding. 
no.  Fl.  77'  Cygni  borcalior  et  pr^ecedens. 
Sept.  17,     Quadruple.     Full  |  degree  n.  preceding  the  17th,  iu 
1783.    a  line  parallel  too-  and  ^j^  Cygni ;  a  fmall  ftar.     The 
two  neareft  extremely  unequal.     JL.  r. ;  S.  d,     Dhlance 
with   625,    13''  54^''.     Poiition    67"   36^  f.   following. 
The  two  largeft  a  very  little  unequal.     Both  r.     Dli- 
tance  with   278,  25^'   S^''-     t'oiitioii  40-^  35''  i^-  ^^l' 

and  low  obfervations,  is  evident  from  forae  meafurcs  I  have  taken  to  afceitain  its 
quantity.  Thus  I  founcl.  May  4,  1783,  that  the  perpendicular  diameter  of  e, 
Flamsteed's  aoth  Sagittarii,  roeafured  16"  9'  ',  while  the  horizontal  was  8"35'"  ; 
which  gives  7"  34""'  for  the  prlfmatic  effeft  :  the  meafures  were  taken  with  460,. 
near  the  meridian,  and  the  air  remarkably  clear.  And  thouglj  this  power,  which 
depends  on  the  obliquity  of  the  incident  ray,  diminiflies  very  faft  in  greater  alti- 
tudes, yet  I  have  found  its  efFcds  perceivable  as  high,  not  only  as  a  or  7  Corvi  in 
the  meridian,  but  up  to  Spica  Virginia,  and  even  to  Regulus.  Experiments  on 
thefe  two  latter  ftars  I  made  November  20,  1782  ;  when  Regulus,  at  the  altitude 
of  49",  fliewed  the  purple  rather  fuller  at  the  bottom  of  the  field  of  view  than 
wheii  it  was  at  the  upper  edge ;  which  fliews  that  the  prifmatic  powers  of  the  edges 
of  the  eye  lens  were  affifted  in  one  fituation  by  the  power  of  the  atmofphere,  bu.t 
counterafted  by  it  in  the  other.  I  turned  the  eye  ions  in  all  fituations,  to  convince 
myfelf  that  it  was  not  in  fault.  This  experiment  explains  alio,  why  a  liar  is  not 
always  beft  in  the  center  of  the  Held  of  view  ;  a  fact  1  have  often  noticed  before  I 
knew  the  caufe. 

V0L.  LXXV.  N  lo^Ying. 


po  Mr,  Herschel's  Caialogui 

III.        lowing.     The  fartheft  very  unequal.     S.  d.     Pofitlon 
almoft  in  a  line  with  the  two  largest. 

1 1  r.  e  (Fl.  46^)  Orionis  borealior  et  fequens. 

Sept.  20,         Treble.     About  ij  degree  n.  following  s,  towards 
i'783.    a  Orionis.     The  two  neareft  of  the  third  clafs. 

1 1  2.  0  (Fl.  18*"^)  Cygni  fequens  ad  auftrum. 

Sept.  22,     Double.     About  i  degree  f.  following  S,  towards  the 
1783.    47th  Cygni;  a  pretty  confiderable  flar.     Equal,  or  per- 
haps the   fouthern  ftar  the  fmalleft.     Both  pr.     Dif- 
tance  with    278,     10''   8"'".     Pofition   71°   o\  f.    fol- 
lowing. 

113.  Fl.  27*"' Cygni  priEcedens  ad  auftrum. 

Sept.  23,  Quadruple  and  Sextuple.  About  |  degree  f.  pre- 
1783.  ceding  the  treble  ftar  I.  96. ;  the  middle  of  three,  the 
moft  north  whereof  is  the  27th  Cygni.  In  the  qua- 
druple or  n.  preceding  fet,  the  two  neareft  very  une- 
qual. Diftance  with  278,  ii^'  i6^^  Pofition  26°  o' 
n.  preceding;  the  two  largeft  almoft  equal.  Both  r. 
Diftance  with  278,  29'^  27'''.  Pofition  5y°  iz'  n.  fol- 
lowing. In  the  fextuple  or  f.  following  fet,  the  two 
largeft  pretty  unequal.  Both  r.  Diftance  with  278, 
19'^  zo"\  Pofition  27°  36'  f.  preceding.  All  the 
other  ftars  are  as  fmall  as  the  fmalleft  of  the  quadruple 
fet,  and  fome  of  them  much  fmaller. 
514,  Fl.  16""  Monocerotis  praecedens  ad  boream. 

Jan.  23,     D-ouble.    About  J|  degree  n.  preceding  the  i6th. 


y  o  u  R  T  1? 


of  Douhk  Sliitf,  ft 


FOURfH  CLASS  OF  DOUBLE  STARS. 

IV.  45.  Ill  pectoris  crate  Ononis. 

Dec.  27,     Double.     About   f   degree   following  i[/,  towards  71 
1781.    Orionis.     Extremely  unequal.     L.  pr. ;   S.   dr.     Dif- 
tance   with    278,    20'^    3'^     Pofition  62°    24.'   f.    fol- 
lowing. 

46.  Fl.  21  ::  Geminorum  *. 

Dec.  27,     Double.     A    little    uaequal.      Both    pr.     Diftancc 

1 78 1,  about  25'^     Pofition 

47.  Fl.  3  Leonis. 

Feb.  2,       Double.     Exceflively  unequal.     L.  r. ;    S.    d.  ;  not 

1782.  vifible  with  227.  Diftance  eftimated  with  460,  about 
24^^.  Pofition  a  little  n.  following.  A  third  ftar  in 
view.  Diftance  perhaps  2'.  Pofition  about  1 5®  f.  fol- 
lowing. 

48.  H  (Fl.  i*"")  Geminorum  praecedens  ad  boream. 

Feb.  6,  Quintuple.  In  the  form  of  a  crofs.  About  f  degree 
1782.  IL  preceding  H  Geminorum,  in  a  line  parallel  to  the 
65th  Orionis  and  f  Tauri ;  the  middle  of  three.  The 
two  nearefl  or  preceding  of  the  five  extremely  unequal. 
Diftancc  20''  57^^^'  Pofition  7°  27'  f.  preceding.  The 
laft  of  the  three,  in  the  fhort  bar  of  the  crofs,  has  an 
excefiiively  obfcure  flar  near  it  of  the  third  clafs.  Five 
more  in  viev%',  differently  difperfed  about  the  quintuple. 

*  The  21  ft  and  aOth  Geminorum  are  not  in  the  heavens  as  they  are  marked  in 
Flamsteed's  Atlas,  fo  that  it  becomes  doubtful  whether  the  N'*^!.  is  right. 

N  2  49- 


Feb.  6,       Double.      I  full:  d^egreen.  following  J  Virgmis,,  in  a 
1782.    line' parallel  to  ^/  and /3' Leonrs.     A  little  unequaL/    L. 
pr.  ;    S.    dr.     Diftance   2^'  28'^     Pofition  56'' 30'f. 
preceding. 
"50".' Fl.  17  Virginis.     In  peflore.  ■; 

*Feb.  6,       Double.     Confiderably  unequal.     L.  w. ;  S.   bluifli. 
1782. ■   Biftance  20'''  l/^^^     Pofition  58^  21^  n.  preceding. 

51.  k  Virginis  :;  Fl.  44  ::  -}-.     In  ala  auftrina. 

Feb.  6,       Double.     A  flar  fouth  of  three  forming  an  arch,  and 
1782.    of  the  fame  magnitude  with  the  middle  one  of  the  arch. 
Extremely    unequal.      L.   w. ;    S.   db.     Diftance.  22'''' 
17^^^;  inaccurate.     Pofition  32^  3^^  i^«  following. 

52.  *  ;  Cancri.  Fl.  48.     In  boreali  forfice. 

Feb.  8,       Double.     Confiderably  imequal.     L.  rw. ;  S.  d.  gar- 
1782.    net.     Diflance  29^^  54^^^   Pofition  2,9''  54^  "•  preceding;, 

a  little  inaccurate. 
CJ3.  TrGeminorum.  Fl.  80.     Supra  capita. 
Feb.  9,      Double.     Exceffively    unequal.     L.   garnet ;    S.    cL 
1782.    Diftance  with  460,   21^^  30^^^     Pofition 
Other  very  fmall  flars  in  view. 

54.  ^  (Fl.  4^"")  Hydras  fequens. 

Feb.  II,     Double.     About    I    degree  following   ^,    towards  ^ 
1782.    Hydras.     Pretty  unequal.     Both  pr.     S.  deeper.     Dif- 
tance 25^''  43^"^^     Pofition  59°  24'  n.  following. 

55.  Fl.  41""  Lyncis  fequens.     In  caudasfine. 

Mar.  5,      Double.     About  3I   minutes  n.  following  the  41  ft" 
1782.    Lyncis.     Extremely  unequal.     L.  r. ;  S.  dr.     Diftance 

15^^  52^^';    a  little  inaccurate.     Pofition   50°  48^  n, 
preceding;  inaccurate. 

t  Perhaps  the  45th  3  require?  fixed  inftraments  to  determine. 


IV.  56.  Fl.  I S  Librae. 

April  3^     Double.     The  following  of  two.     Extremely  uiie- 
1782.    q^^''^l«     L.    r.  ;    S.    b.     Diilauce    i  f   59"^^     Pofitioa 
44°  45^  11.  following. 

57.  Fl.  42'™  Ccmie  Berenices  fequens  ad  auflriim. 

April  15,     Double.     About  3  degrees  f.  following  the  42dComis- 
■  1782.    Berenices  towards   v  Bootis ;  the  vertex  of  an  ilofceles^ 
triangle.      Extremely    unequal.      Diftance   with    625^, 
16'^  42^^''.     Pofition  46°  31^  f.  preceding. 

58.  Fl.  36*"'  Comae  Berenices  priEcedens  ad  boream. 

April  18,     A  pretty  double  ftar.     About  2!  degrees  n.  preceding 

i''82.    the  36th,  in  a  line  parallel  to  the  42d  and  15th  Coma^ 

Berenices  ;  the  following  of  two  unequal  ilars.    A  little 

unequal.      Both   rw.      Diftance    15''    52^"^      Pofition 

67°  ^y^  f.  preceding. 

5p.  Prope  a  Lyrs. 

May  12,     Double.     About  2  or  3  minutes  f.  preceding  a  Lyraj. 
1782.    Very  unequal.     Bothd.     Diftance  with  278,  22^^  20^^^ 
Polition  2^°  57^  n.  preceding.     Pofition   of  the  largeft 
with  regard  to  a,  Lyra^  59°  12^  f.  preceding, 
'60.  Fl.  4=""  Urfae  majoris  fequens  ad  boream. 
June  6,       Double.     Near  i  degree  n    following  the  4th,  in  ar 
1782.    Ihie  parallel  to  0  and  h  Urfae  majoris;  a  pretty  larg^ 
ftar.     Extremely    unequal.      L.    r. ;    S.    d.      Diftance 
near  30'''' ;  but  too  obfcure  for  meafures. 
t)i.  ^(Fl.  7^)  Coron^eauftralior  et  praecedens. 
July  18,      Double.     Near  |   degree  f.  preceding  f,  towards  ^ 
1782.    Coronae    bor.      Nearly    equal.      Both    pr.      Diftance 
16'^  46'^^.     Pofition  4°  57' n»  following,. 

^2. 


94  ^^>  Herschel's  Catalogue 

IV.  62.  T  (Fl.  22^)  Hercnlis  anftralior  et  fequens. 
Aug.  II,      Double.     About  2|  degrees  f.  following  r  Herculls, 
1^82.    ill   a   line   parallel  to  f  and  y  Draconis ;  a  confiderable 

ftar.     Very    or    extremely    unequal.     L.    w, ;    S.   br. 

Diftance  16'^  S^'^^-     Pofition  72°  I5^f.  preceding. 

63.  Fl.  42  Herculls.     Dextrum  fupra  genu. 

Aug,  IT,     Double.     V^ery  unequal.     L.   r. ;  S.   rw.     Diflancc 
1782.    21^^  31^'^     Pofition  3^"  42^  f.  following. 

64.  Prope  q  (Fl.  12^'")  Perfei. 

Aug.  20,      Double.     Within  a  few  minutes  of  q  Perfei.     Pretty 
1782.    unequal.     Both  pr. ;  but  S.  a  little  darker.     Diftance 
^l'^  59^^^     Pofition  ^'j'^  57^  f.  preceding. 
6^.  Prope  Fl.  :^^"'  Cafliopeias- 

Aug.  25,     Double.     Within   1,0  minutes  of  the  3d  Caffiopeis. 
1782.    Very   unequal.     L.   pr. ;    S.    r.     Diftance    20^^46^^'; 
very  inaccurate.     Pofition  41°  12^  f.  following. 

66.  0  (Fl.  "^"^^"^^  Caffiopeias  piraecedens. 

Aug.  28,     Double.     About    1 1    degree  f.  of,  and  a  little  pre- 
1782.    ceding^,  in  a  line  from  5  continued  through  Q  Caffio- 
peias.    Extremely  unequal.     L.  r. ;    S.   db.     Diftance 
24'^  2^^';     very  inaccurate.     Pofition   13°    12.  n.  fol- 
lowing ;  inaccurate. 

67.  t  Fl.  40  et  41  Draconis. 

Aug.  29,     Double.     A  little  unequal.     L.  rw. ;    S,  pr.     Dif* 

1782.    tance  20^  39^''^  mean  meafure;  very  accurate.     Pofition 

^f  I5^f.  preceding*.     There  is  a  third,  mach  fmallcr 

flar.      Diftance  3'   16''  ^i''\      Pofition  about  30°  f. 

following . 

♦  The  proper  motion  of  one  of  thefe  ftars  at  lead  fince  the    time  of  FlaaT- 

STEED  is  evident,  as  he  gives  us  their  difference  in  J9^  2',  and  in  PD  3'  5''.  Pofi- 
tion f.  preceding.  Hence  we  have  the  hypotcnufe  or  diftance  above  3'  40", 
inftead  of  20"  39'" ;  and  the  angle  86°  17'  inilead  of  35°  15'. 

4  68. 


of  Double  Stars.  ^^ 

IV.  68.  Fl.  77  Plfcium.     In  lini  flexii. 

Sept.  3,       Double.     A   little  unequal.     L.   wr.  ;  S.   pr.     Dif- 
1782.    tance  29^'  36^^^     Pofition  4"^  48^  n.  following.  In  both 
meafures  the  weather  too  windy  for  accuracy. 

69.  Fl.  23""  Andromedas  prascedens. 

Sept.  4,      Double.     Full  1 1  degree  preceding  the  23d,  in  aline 

1782.    parallel  to  v  and  t  Andromedas.     Of  two  double  ftars 

in  the  finder  the  largeft  of  the   preceding  fet.     Very 

unequal.     L.  r.  ;  S.  d.     Diftance  with  278,  21^^  58^^^ 

Poiition  70°  36'  n.  preceding. 

70.  Fl.  51  Pifcium.     In  aullrino  lino. 

Sept.  4,      Double.     Very  unequal.     L.  rw. ;  S.  d.     Diftance 
1782.    with  278,  22^^  29^^^     Pofition  0°  36^  n.  following. 

71.  *  0  Capricorni.  Fl.  12.     Trium  in  roflro  auflrina. 

Sept.  5,      Double.     Pretty  unequal.     Both  rw.     Diflance  23,^' 
1782.    30^'^^.     Pofition  30^45^  f.  preceding. 

72.  Fl.  ^§^  Perfei borealior. 

Sept.  7,      Double.     About  |  degree  n.  of  the  55th  Perfei;  of 
1782.    three   in  a  line  the  moft  north.     Pretty  unequal.     L^ 

rw. ;  S.  pr.     Dillance  with  278,   16^^51/^'.     Pofition* 

27""  24'  n.  following. 

73.  In  Conftellatione  Camelopardali. 

Sept.  7,      Double.     Between  Fl.  2  and  8  Cam. ;  the  fmallefl: 
1782.    of  two  that  are  within  |  degree  of  each  other.     Confix 

derably  unequal.     Diftance  19/^  32.^^^     Pofition  85°  a- 

f.  preceding. 

74.  ^  (Fl.  68^'")  Tauri  fequens  ad  boream. 

Sept. 7,      Double*     Near   |   degree  n..  following^,  towards^;. 
1782.    Tauri.     Very  unequal.     L.  pr. ;  S.  r.     Diftance  1.6^'' 
31'^^     Pofition  25°  45'  n,  following. 

75* 


«>i5"  Jfr.  Herschei/s  Gi^^%?^f 

IV.  75.  ^  (Fl.  66""^)  Tauri  fequeus. 

..iiept.  7»      Double.     About  1 1  degree  n.  following  r,  in  a  lioe 
17-82.    parallel  to  jw  Tauri  and  the  9th  Orionis.     Very  une- 
qual.    L.    r. ;    S.   dr.     Diftance   22'^    25^^^'     Po^^tioii 
6 1°  36M'.  following. 
*76.  Fl.  13^""  Ceti  praecedens  ad  auftrum. 
Sept.  9,      Double.     About   i    degree   f.    preceding  the    i3tlT^ 
X782.    towards  the  8th  Cetl.     Confiderably  unequal.     L.  rw.  ; 
S.  br.     Diftance  with  278,  18'^  55''''.     Pofition  40°  24'' 
n.  following. 

77.  Fl.  37^  Ceti  borealior.     In  dorfo. 

Sept.  22,     Double.     About  J   degree  n.  preceding    the  37th, 

1782.    towards  the  36th  Ceti.     Very  unequal.     L.  r. ;  S.  dr. 

Diftance  19'^  6^^\     Polition  63°  24^11.  preceding. 

78.  ;j  (Fl.  3'"')  Cephei  praecedens. 

Sept.  27»     Double.     About    1 1   degree   preceding  ;?,  in  a  line 
i^Sz.    from    6   continued  through  tj  Cephei.     Very  unequal. 
L.  r. ;  S.  d.     Diftance  ig''  32^^''.     Pofition  40°  36'  n, 
following. 

79.  I/,  Cephei.  Fl.  13.     Ad  coronam. 

Sept.  27,     Double.     A   little  unequal.     L.  \V. ;  S.  rw.     Dif* 
1782.    tance  21^^  3^'^     Pofition  7 7^"  48^  f.  preceding. 
So.  (3  (Fl.  2^)  Canls  majoris  borealior. 

Sept.  30,     Double.     About   1 1   degree  n.  of  /3  Canis    majoris 
1782.    towards    the   nth  Monocerotis ;  the   moft  n.  of  two. 
Confiderably  unequal.     Diftance    17^^   59'^''*    difficult 
to  take,  and  perhaps  a  little  inaccurate.    Fofition  2°  24'' 
n.  following. 
Si.  1/ Canis  majoris.  Fl.  6.     In  dextro  genu. 
Sept.  30,     Double.  Confiderably  unequal.    L.  f w. ;  S.  pr.   Difl. 
1782,    1 8'"  1 9'''.     Poiition  very  near  diredly  preceding. 

I  §2. 


cj  Double  S/ars,      ^  §"/ 

IV.  82.  Prope  Fl»  i6»"'Cephei.     In  cingiilo. 
Sept.  30,     Double.  ■  Above  I  degree  following  the  i6thCephei, 
1782.    ill  ^  li'ie  parallel  to  /3  and  «  Caffiopeiae.     Confiderably 
unequal.     L.  orange.     S.  r.     Diftaiice'  28^'  ^'^\     Poli- 
tion  79°  18^  n.  preceding. 
8 J.  Fl.  26  Ceti.     Supra  dorfum. 
oa.  2,     Double.     Very  unequal.     L.    rw.     S.  db.     Diftance 
1782.    17^^  2'^^  mean  mealure.     Poiition  i^'^  ^6'  i.  preceding. 

84.  ;«  Orionis.  FL.23     In  crate  pe£loris 

06V.  2,      Double.      Confiderably    iwiequal.      L.   w. ;    S.    pr* 
1782.    Diftancc  with  278,  26^'  g'^\     Pofition  59.^  33  ^'  fol- 
lowing. 

85.  Fl.  ultima  Lacertae. 

06t.  4,      Treble.     The  two  nearefl:  extremely  unequal.     L. 

'  1782.  •  fw. ;  S.  d.     Diflance    20^' 27'^^     Pofition  79^"  53^  n. 

preceding.     The  next  very  unequal ;   S.  r .     Diftancc 

54^^57^'^;  inaccurate.     Pofition  44°  24' n.  following, 

A  fourth  and  fifth  ftar  in  view. 

86.  Fl.  8  Lacertae.     In  media  cauda. 

oa.  4,      Quadruple.     The  two  largeft  and  neareft  a  little  une- 
1782.    qual.     Both  rw.     Diftance    17^^   i^'^\     Pofition    84° 

30^  f.  preceding.     The  two  next  very  unequal,  of  the 

fourth  clafs.     The  two  remaining  confiderably  unequal, 

of  the  fifth  clafs.     They  form  an  arch. 
Byv}e  (Fl.  29'"')  Orionis  prascedens.     In  finiftro  calcaneo. 
oa.  4,       Double.     About  i  degree  preceding  e,  in  a  line  pa* 
1782.    rallel  to  a-  Orionis  and  b  Eridani  nearly.     Confiderably 

unequal.     Both  pr.     Diftance  29^''  i8''^     Pofition  8  2^* 
r,  ni  18'  n.  following. 

Vol,  LXXV.  O  88. 


9?  Mr.  Herschel's  Catalogue 

IV.  88.  Fi..  7  Tauri.     In  dorfo. 

c&.  9,       Double,     Very  unequal.     L.  pr. ;  S.  dr.     Diftancc 
1782.     19'^  S'^^^^*     Pofition  23°  15^  n.  following. 

89.  E  telefcopicis  caudam  Arletis  fequentlbus. 

oa  9,       Double.     The  vertex  of  an  ifofceles  triangle  follow- 
1782.    ing  T  Arletis;  a  very  fmall  ftar.     Very  unequal,     li,' 

r.^    S.   d.     Diftance    with    278,    20'^  3'''^      Pofitiou 

62°  o'  f.  following. 

90.  Ad  Fl.  18*"*  Urfae  minoris.     Prope  edu6lionem  caudae. 

oa.  12,     Double.     The  largefl:  of  fix  or  feven  ftars,  and  moil; 
1782.    fouth  of  a  triangle  formed  by  three  of  them.     A  little 

unequal.     L.  pr.  ;  S.  deeper  pr.     Diftance  2^(>^^  z\"\ 

Pofition  3°  1 2'  n.  following. 

91.  Fl.  2  Navis. 

oa.  12,     A  pretty  double  ftar.     A  little  unequal.     L.  w. ;  S. 
1782.    w.  inclining  to  r.     Diftance   i']"  23'^'.     Pofition  69** 
12'  n.  preceding. 

92.  /3  inter  et  ^  Delphini. 

oa.  i-].     Treble.     Between  /3  and  X,->  hut  nearer  to  /9  Delphin\. 
1782.    All  three  nearly  equal.     AH  ,wr.     Diftance  of  the  tWQ 

neareft  with  278,  zi"  2)2>" '     Pp^iUou  18"*  27'  n,  pre^, 

ceding. 

93.  E  (Fl.  4*™)  Lyrae  fequens.  .  \,  ; 

oa.  19,     Double.     About  3  degrees  following!  «,  in  a  line  pa« 
1782.    rallel  to  ex.  and  5  Lyrae ;  the  largeft  of  two.     Extremely 

unequal.     L.  w. ;  S.  r.     Diftance  19'^  50''^     PofitioaL  > 

24°  o^  f.  preceding. 

94.  E  borealibus  telefcopicis  jQL.yraE  prascedentibus. 

oa.  19,     Double.     Full  2  degrees  n.  preceding  /S  Lyras,  in  a 
3782-    line  parallel  to  the  18th  and  e ;  the  fixth  telefcopic  ftar. 

CoaliderabJy 


tf  Double  Stars,  99 

IV;       Confiderably  unequal.     L.  rw.;  S.  pr,    Diftancc  22" 
$'^'^\     Pofitlon  5°  24'  n.  following. 

95.  Fl.  25""  Monocerotis  priccedens. 

oa.  19,  Quadruple.  About  2I  degrees  preceding,  and  a  little 
1782.  n.  of  the  25th  Monocerotis.  Two  large  ftars  always  to 
be  feen,  and  two  more  only  vlfible  in  dark  nights.  The 
nearefl:  which  is  that  to  the  fmallefl:  of  the  two  large 
ones,  extremely  unequal.  Diftance  20''  ^l' ' '  Pofi- 
tioii  following. 

96.  Fl.  25*"  Monocerotis  fequens.     In  latere. 

oa.  19,     Double.     About  i|  n.  following  the  25th,  in  a  line 
1782.    parallel  to  the  2ifl:  Monocerotis  and  Procyon.     A  little 

unequal.     Both    dr.      Diflancc.  18'^     ^9^^^*      Pofitiou 

24*^0' f.  preceding. 

97.  Fl.  29  Monocerotis.     In  femore. 

Odi.  19,     Double.     Extremely  unequal.     L.  wr. ;  S.  d.     Dif^ 
1782.    tance  29^^  54^'^     Pofition  15''  12''  f.  following.     Six 
more  in  view, 

98.  oi  (Fl.  58^"")  Orionis  ad  aufbrum  praeiens. 

Oft.  29,     Double.     About   |   degree  preceding  a,    towards   ^ 
1782.    Ononis.     Equal.     Both  r.    Diflance  17^' 59^^^;  a  little 
inaccurate. 

99.  Duarum  telefcopicarum  ^  Sagittas  ad  auftrum  fequentium 
borea, 

Nov.  6,  Treble.  Of  a  trapezium,  confining  of  this  treble 
1782.  ftar,  J",  ^,  and  the  9th  Sagitt^,  it  is  the  corner  oppofite 
to  ^;  the  neareft  to  f  of  two.  The  two  neareft  very 
unequal.  L.  pr. ;  S.  db.  Diftance  21'^  22'^^;  Inac- 
curate. Pofition  0°  o'  following.  The  two  largefl  a 
little  unequal ;  of  the  fifth  clafs.  Pofitloa  10^  36'  f. 
preceding. 

O  2  100*. 


Joo  Mr,  Her scH el's  Catalogue 

IV.   ICO.  %  Sagittae.  Fl.  13.     Infra  mediam  arundinem. 

Nov.  6,       Treble.     The   largeO;  of   three.      The  two   iiearert: 

1782.    equal.     Both  r.     Dii1:ance23''' 2'"^     Pofition  10°  12^  f. 

precedhig.     The  third  is  a  large  fliar.     Diftance  above 

I   minute.     Pofitioii   about   10°  or  15°  n.  preceding  the 

other  two. 

10 1.  <p  (Fl.  24*)  Auriga  borealior  et  pra?cedens. 

Nov.  6,       Double.     Near   %    degree  n.   preceding  (p,  in  a  line 
1782.    parallel  to  the  2 1  ft  and   8th  Auriga^.     Pretty  unequaL 

L.    rw.      S.    bluifh.      Diftance    25'^    2.<^"\      Poiitioix 

76°  o'  n.  preceding. 

102.  Fl.  _^c^  Auriga. 

Nov.  6,       Double.     The  apex  of  an  ifofceles  triangle.     Very 
1782.    or  extremely  unequal.      L.   rw.  ;     S.  Diftance 

23'^  30^^^     Position  50°  3'  f.  preceding;. 

103.  Fl.  77^'"  Draconis  fequituri 

Nov.  13,      Double.     Near  \  degree  following  the   77th  Dra- 
1782.    conis,  in  a  line  parallel  to  x,  Cephei  and  the  76th  Dra- 
conis  nearly ;  of  a  re£langular  triangle  the  leg  neareft: 
the   77  th.     Very  unequaL     L.  r. ;  S.  bluiih  r.     Dif- 
tance 22^'  o^^'^     Poiition  45°  48^  n..  following. 

104.  Inter  y  et  55*'"  Andromedas. 

Nov.  13,      Double.     A  little  more  than  i    degree  n.  following 
J78».    the  55th  Andromedae,  in  a  line  parallel  to  /3  Trianguli 
and  Algol.     Confiderably  unequal.     L.  r. ;  S.  d.     Dif- 
tance with  278,   \%"  ^f'\     Pofition   22°  33'  n.  fol- 
lowing. 

105.  ^Corvi.  Fl,  7.     Duarum  in  ala  fequente  prscedens. 
Nov.  13,      Double.     Extremely   unequal.     L.  w. ;  S.  r.     Dif- 

1782.    taace  23'^  ^o^'\    Pofition  54°  o^  f,  preceding,  , 

106, 


of  Double  Sfcirs,        '  lo*)^ 

IV.   io6.  a.  (Fl»  50"^)  Urfae  majoris  fequens  adborcam. 

Nov.  17,     Double.     About  1 1  degree,  n..  following  a^  in  a  liner 

1782.    parallel  to  /3  Urfys  et  ;c  Draconis ;  the  lafl:  oi  three  in  a 

row.      Extremely   unequah      Both    r.      Dlflance    18''' 

55^^^;  verj   inaccurate.     Pofition  44"*  33^  f.  fallowing. 

A  third  Imall  flar  in  view. 

107.  Fl.  79^  Pegafi  auflrahor  et  priecedens. 

Nov.  20,  Double.  About  |  degree  f.  preceding  the  79tht, 
1782.    towards   r   Pegafi;  at   the    center   of  a  trefoil.     Very 

unequal.     L.  r. ;  S.  d.    ,  Diftauce  with  278,   26'^l2'/. 

Polition  50°  21'  n.  following. 

108.  Fl.  69*  Urfae majoris  auilralior.  r 

Nov. 20,  Double.  Near  2  degrees  f.  of  the  69th,  .tov/ards 
1782.    the  63d^Urfa2  majoris.     A  very  little  unequal.     Both  r. 

Diftance  19'''  15'^^ ;  very  inaccurate.     Pofition    10°  12'^ 

n.  following.  . 

109.  Fl.  62Tauri.. 

Nov.  25,  Double.  Coniiderably  unequal.  L.  w..;  S.  r.  Dif- 
1782.    tauce  28'''  ^'^'.     Pofition  21°  12'  n.  preceding. 

no.  j6  (Fl.  112^)  Tauri  berealior  et  fequens.: 

Pec.  24,      Double.     About    i|    degree  n.    following  /G  Tauri>, 

1782.    towards  6  Aurigas ;  the  fecond  in  that  diredlion.     Very 

•unequal.     L.  r. ;  S.  d.     Diftance.  id^^  i^^\     Pofition 

rri  ;v.    7-4°  54' "•  pi-eeeding. 

111.  Fju.  54  Cancfi. 

Dec.  aS,     Double.     A   little  unequal.     Both  rw.     S.    a  little 

1782.  darker.     Distance   17'^   14'^%     Pofition   29°  a'   £   fol 
lowing.  ,       r  ; 

112.  -y  (Fl.  15^"')' Crateris  fequens  ad  borearru 

Jan.  i^       Double.     About  I  degree  n..  following  y  Craterls,  in 

1783.  a  line  parallel  to  I  Corvi  and  Spica.     Equah     Both  pr^ 

Diftancc 


lOi  Mr,  HersChel*s  Catalogue 

IV.       Dlftance  26'^   15'"';  too  low  for  accuracy.     Pofitloti 
58°  42^  n.  preceding  or  f.  following. 

113.  Fl.  61^  Cygni  borealior  et  praecedens. 
Jan.  6,      Double.     About   1 1  degree  n.  preceding  the  6 1  ft,  in 

-1783;  a  line  parallel  to  u  and  a  Cygni.  Very  or  extremely 
unequal.  L.  r.;  S.  db.  Diftance  with  278,  i  7'' 30''^ 
Pofition  28°  24'  n.  preceding.     A  third  ftar  in  view. 

,114.  t  (Fl.  12')  Virginia  auftralior. 

vjam  8,      Double,     About  ij  degree   f.  of  f  Virginis.     Very 
1783.    unequal.     L.  pr. ;  S.  d,     Diftance  23'^  21^^''.    Pofitioii 
15°  54^  n.  preceding. 

1 15.  (p  (Fl.  1 1*"")  HercuUs  praecedens  ad  auftrum. 
Jan.  !o,     Double.     About  2|  degrees  f.  of,  and  a  little  pre- 
J783.    ceding  ^,  in  a  line  parallel  to  ij  and  ^  Herculis;  the 
largeft  of  three  or  four.     Extremely  unequal.     L.  r. ; 
S.   b.     Diftance   20'''   54'^^     Polition   43°  48^  n.  fol- 
lowing. 

116*.  Fl,  83*"  Pegafi  fequens  ad  boream. 

Jan.  13,      Double.      Equal.      Both   w.      Diftance  28''   59^^^* 

i;83.  Pofition  68°  21^  Mr.  C.  Mayer,  in  1777,  fettled  its 
place  j^o^^  52^  ^^^^  in  time,  and  20*  17'  ^^'^  in  de- 
clination N. 

117.  Fl,  42^  Eridani  auftralior. 

Jan.  31,      Double,     About  i|  degree  f.  of  the  42d  Eridani,  in 
1783.    a  line  parallel  to  Rigel  and  jt*  Leporis;  the  moft  foutl'i 
and  following  of  three.     Very  unequal.     L.  r. ;  S.  r* 
Diftance  19^^  32^^^*     Pofition  31°  48'  f.  preceding. 

118,  <  (Fl.  48"^)  Cancri  fequen?, 

Feb.  5,      Double.     Full  |  degree  following  the  48th,  in  a  line 

1783.    parallel  to  §  Cancri  and  e  Leonis;  a  very  fmall  ftar, 

next  to  two  more  which  are  nearer  to  t,     A  little  une- 

7  qual. 


of  D'ouhle  Stan,  102 

IV.       qual.     Diflance  24^''   (i''\     Pofition  about  23°  n.  fol- 


lowing. 


1 19.  i  (Fl.  bS""*)  Virginis  prsecedens  ad  auftrum. 

Feb.  7,      Double.     About  1  degree  f.  preceding  the  68th,  in  a 
1783.    line  parallel  to  the  99th  and  »  Virginis.     Extremely 

unequal.      Diflance  z\''  49 "^^     Pofition  36°   54'  n. 

preceding. 

120.  Fl.  82*""  Pifcium  fequens  ad  boream. 

Feb.  37,     Double.     About  |  degree  n.  following  the  82d  Plf- 
1783.    cium,  in  a  line  parallel  to  a  and  /Q  Trianguli ;    the 

largeft  of  two.     Confiderably  unequal.     L,  rw.  \  S  pr. 

Diftaiice   i*^"  \()'^\     Pofition  21°  o^   f.  preceding.     A 

third  flar  in  view. 

121.  c-  Scorpii  Fl.  20.  pr^ecedens  trium  lucidarumin  corpore. 
M?r.  I,       Double.     Very  unequal.     L.   whitifh ;  S.   r.     DIf- 

178^.    tance  21^^40^'''.     Pofition  o*'  o^  (or  perhaps  1°)  n.  pre- 
ceding. ' 

122.  Fl,  32*  Ophiuchi  borealioret  praecedehs. 

Mar.  7,      Double.     Near  i  degree  n.  of,  and  a  little  preceding 
1783.    the  32d  Ophiuchi,  in  a  line  parallel  to  a,  and  -n  Herculis. 

Very  unequal.     DiJftance  21:''' 3''^^,     Pofition  25°   3  f. 

preceding, 

123.  Fl.  19  Ophiuchi. 

Mar.  9,      Double.     The  mtjfl  fouth  of  two.     Very  unequal- 
3783.    L.  pr.;  S.  d.     Diftaiice  20^^  ^f^\     Pofition  3°  9''  f, 
following. 

124.  ^  (Fl.  4?"")  Ophiuchi  prsecedens  ad  auflrum.         • '      -c^^ 
Mar.  24,      Double.   About  I  degree  preceding  and  a  little  f.  of  ip, 

J 783.    in  a  line  parallel  to  ij^' Ophiuchi  and  &>  Scorpii;  in  the 
bafe  of  a  triangle,  the  neareft  to  x]/.    A  little  unequal. 

%  Both 


*3^4  ^^«  Herschel's  Catalogue 

!¥,,_      Both   inclining  to   r. .   Diftance    15'^    14.''',     Pofitioii^ 
62^  54^  n.  following. 

125.  Fl.  29  Camelopardaii. 

April  2,  Double.  Very  unequal.  •.  L.  pr. ;  -S.  d.  Diftance' 
1783.  22''  2 6^''-;,' very  inaccurate.  Pofitioiv  47^  36'.  f.  fot* 
,fi    j^  lowing;  a  little  iji  accurate. 

126.  A  (Pl.  22*)  Cephei  borealior  et  praecedens. 

April 20,     Double.     Lefs   than- 1  "degree  n.  preceding  A,  in  a  " 
1^.83.    line  almoft  parallel  to  I  and  f  Cephei;  a  confiderable - 
gff^j    ^fiAi".  .  A  little  unequal.     Bothdw.     Diftance  18''' 50'^^ 
PofitIon45'^  39'  n.  preceding. 
3  27  t«  A  (Fl.  16*™)  Aqullse  fequens  ad  boream. 
May  21,     Double.     About  2§  degrees  n,  following  the  farthefl: 
5783.    of  two  which  are  about    if  degree  from  x,  in  a  line- ' 
parallel  to  X  and  ^  Aquilae.     Very  unequal.     L.  rw.  ;'* 
S.  dr.     Diftance  1 7^^  14^^^;  more  exad  with  932,   15^'' 
S'^'^\     Pofition  69°  54^*  n.  preceding.     Mr.  Pigott, 
who  favoured   me   with   it,    gives   its  place    J^    iZ^~i 
^2.^i  =t.  Declination  i"  o^  S.  - 
I2S.  y  (Fl.  57*""),  Andromedae  praecedens  ad  auflrum. 
juiy.28,      Double.     About    i|   degree   f.  preceding  y  almoil: 
3783.    towards  (3  Andromedas;  moreexa£l  towards  o-Pifcium; 
one  not  in  a  row  of  ftars  which  are  near  that  place. 
._;Confiderably  unequal.     L.  pr. ;  S.  dr.     Diftance  15'' 
":  ■  42^'^     Pofition  24°  12'  n.  following. 
129.  Fl.  59  Andromedae. 

July  28,      Double.     A  little  unequal.  '  L.  rw. ;    S.  pr.     Difr  ^ 
17^.    tance  15''.  l/-.^;  Pofition  ^^^^  9^  n.  following.    A  third 
Of: J  &H  ii^  view  ^b^ut,  58°  or  iSp°  f,  preceding* 
.L:f;p3irj     '"'-f  A     .\{;  cj    '•  ■;    "   ■  ^''  . 
dvM  I  IJO. 


cf  Double  Stars,  105 

IV.  130.  VI  (Fl.  99*)  Pifcium  borealior  et  fequens. 
Aug.  2,      Double.     About   i|   degree  11.  of,  and  a  little  fol- 
1783.    lowing  y\  Pifcium,  in  a  line  parallel  to  /3  Arietis  and  /3 
Trianguli ;  the  lafl:  of  four  in  a  crooked  row.     Very- 
unequal.     L.    r. ;    S.   darker   r.     Diftance    with   278, 
\<^"  \^'"»     Pofition  62°  15'  n.  following. 

13 1.  Fl.  100  Pifcium. 

Aug.  2,       Double.     Pretty  unequal.     L.   pr. ;  S.  r.     Diftancc 
1783.     15^^  S"^'" *     Pofition  5°  o'  n.  following. 

132.  Fl.  46*""  Aquilae  fequens  ad  boream. 

Aug.  6,      Double.     About  \  degree  n.  following  46  Aquilae,  in 
1783.    a   line  parallel    to  ot.   and  y  Sagittas.     Very  unequal. 

L.  r. ;  S.  db.     Diftance    zz"  44'^'.     Pofitioii  41°  24^ 

n.  preceding. 


FIFTH     CLASS      OF     DOUBLE     STARS. 

V.  52.  Secunda  a  v  Geminorum  jt*  verfus. 
Dec.  27,     Double.     The  fecond  ftar  from  v  towards  y.  Gemino- 
,781.    rum.     Pretty  unequal.     L.  r. ;  S.  b.     Diftance  OiS' ' 
inaccurate. 

53.  p  Geminorum.  Fl.  (i'}^.     In  Inguine  fequentls  H'. 

Dec.  27,     Double.     The  brighteft  of   two.     Extremely   une- 
1781.    qual.     L.  pr.  ;S.  d.     Diftance  44'''  1 5'^^. 

54.  5  Hydrae.  Fl.  22.     Duarvim  in  edu6lione  cervlcis  fequens. 
Jan.  20,     Double.     Exceffively  unequal.     L.  w. ;  S.  a  point. 
,782.    Diftance  near  i    minute,  too  obfcure  for  meafures,  and 

Vol.  LXXV.  P  not 


io6  Mr.  He-r^chel\  Catalogue 

V.  not  vifible  till  after  having  looked  a  good  while  at  §), 

PofitioQ  about  y^°  f.  following. 
^^.  Ad  Fi.  1 2^™  Geminorum.     In  pede  Jl'  praecedentis  liniflro. 
Jan.  30,     Treble.     A   fmall  ftar  near  the   place  of  the   12th 
1782.    Geminorum.     The  two  neareft  a  little  unequal.     Dif- 
tance  lefs  than  i\ 

56.  Fl.  15  Geminorum.  Dextrum  prioris  Jl^  pedem  attingens* 
Jan.  30,  Double.  Conliderably  or  very  unequal.  L.  r. ;  S.  d, 
1782.    Diftance  32^^  39^^^*     Pofition  near  60''  f.  preceding. 

57.  Fl.    9^   Orionis    borealior   et   fequens.       In    exuviarum 
fummo. 

Feb.  4,  Treble.  More  than  i  degree  n.  following  the  pth 
1782.  Orionis,  towards  the  1 13th  Tauri ;  the  largeft  of  two. 
The  two  neareft  confiderably  unequal.  L.  rw. ;  S- rw* 
Diftance  with  278,  36^'  26'^^  Pofition  ^f  36'.  The 
farthefl  very  unequal.  S.  r.  Diftance  Vth  Clafs.  Pq- 
iition  following. 

58.  Fl.  y  Leonis.     Supra  pedem  borealem  anterlorem. 

Feb.  4,       Double.     Very  unequal.     L.   rw. ;  S.  r.     Diftance 
1782.    42^^  25'^^     Pofition  8°  36'  n.  following. 
^g,  ^  Cancri.   Fl.  31.     In  quadrilatero  circa  Nubem. 
Feb.  6,       Double.     Extremely   unequal.     L.  r. ;    S.   d.     Dif^ 
1782.    tance  44^^  5^'^^*     Pofition  n.  following* 

60.  0  (Fl.  95^"")  Leonis  praecedens ;  ad  caudam. 

,  Feb.  9,       Double.     Near  |  degree  f.  preceding  the  95th,  in  z 
,782.    line  parallel  to  jS  and  ^  Leonis.    Very  unequal.     L.  rw. ;. 
S.  d.     Diflance  37''  15'"'^    Pofition  70°  48'   n.  fol- 
lowing. 

61.  Fl.  81  Leonis.     In  clune. 

Feb.  9,      Double.     Extremely  -unequal,     L.  rw. ;  S.  r.     Dif- 
1782,    tance  57^^  23'''^     Pofition 

2  »  62, 


of  Double  Stars,  lo^ 

V.  62.  Fl.  ^"^  Leonis.  E  poflerlores  pedes  prxcedentibus. 
Feb.  II,  1782.     Double.     Very  unequal.     Diftance  33'^  16 '^^ 
6^,  Fl.  25  Leonis.     In  inhmo  pe^lore. 

feb.  17,     Double.     The  largefl  of  two.     Extremely  unequal. 
1782.    L.  pr,  ;   S.  d.     Dlftance  52'^  46^^^     Pofition 
64.  Fl.  43^'  Leonis   auftralior.     Ad  liniftrum  anteriorem  cu- 

bitum. 
Feb.  17,     Double.     Near  r  degree  f.  of  the  43d,  in  a  linepa- 
1782.    rallel  to  ^  and  a  Leonis.     Extremely  unequal.     L.  w. 
inclining  to  r. ;  S.  db.     Diflance  59^^  40^^^.     Pofition 
6^.  Secunda  ad  tt  Canis  majoris.  Fl.  17.     Li  pe6lore. 
JMar.  3,       Treble.     The   two  nearefl  very  unequal.     L.   rw. ; 
1782.    S.  r.     Diftance  44^^  52^^^     Pofition  64^  12^  f.  following. 
The   two  tarthell:  very  or   extremely  unequal.     S.    r. 
Diflance  Vth  Clafs.     Pofition   about  85°  f.  preceding. 
The  three  liars   form  a  redangle,  the  hypotenufe  of 
which  contains  the  largeft  and  fmalleft. 

66.  f  (Fl.  63^)  Geminorum  borealior. 

Mar.  3,      Double.     About   |   degree  n.  of,  and  a  little  prc- 
1782.    ceding  />,  in  a  line  parallel   to   u  and  a,   Geminorum. 

Very   unequal.     L.   pr. ;    S.  d.     Diftance    34''  39^"' 

Poiition  1°  or  2°  n.  preceding. 

67.  Pollucem  prope.     In  capite  fequentls  If'. 

Mar.  3,       Double.     Near    i   degree  n.  following  /3,  in  a  line 
J7S2.    from   (J  continued  through  /3  Geminorum  nearly;  the 

farthefi:  and  fmallefl  of  three.     Confiderably   unequal. 

L.  r. ;  S,  dr.     Diftance  47^^  sY'^^ 

68.  Fl.  75*"^^  Leonis  prsecedens  ad  boream. 

Mar.  5,      Treble.     One  of  two  n.  preceding  the  75th,  m  a 
?782.    line  parallel  to  the  84th  and  59th  Leonis,     The  two 

P  2  neareft 


loS  Mr.  Herschel's  Catalogue 

V.  iieareft  very  unequal.     Diftance  54'^  ^f\     The  far- 

thefl  extremely  unequal. 

69.  Fl.  n  LeoQis  minoris.     In  extreme  anteriore  pede. 

Mar.  12,     Double.     The  largefl  of  two.     Extremely  unequal. 
1782.    L.  pr.  ;  S.  r.     Diftance  58^'  i^'". 

70.  Fl.  2^'"  Bootis  prj::£cedensad  boream. 

Apiil5,       Double      Near  3  degrees  n.  preceding  the  2d  Bootis* 

1782.    towards  the  43d  Comx^  Ber.  ;  the  preceding  of  three  in 

a  line  parallel  to  »   and  t]   Bootis.     A   little  unequal. 

L.  r.  ;  S.  darker  r.     Diilance  56''  S^  "'     Pohtion  7°  o' 

f.  preceding. 

71.  Prope  y  (Fl.  24^'")  Gemlnorum. 

April  15,     Double.     Three  or  four  minutes  n.  preceding  7  Ge- 
1782.    minorum.     Of  the  Vth  Clafs.     More  in  view. 

72.  -f*  wHerculis.  Fl.  36  6137.    In  finiftro  Serpentarii  brachio. 
May  18,     Double.     A  little  unequal.     L.  bluifh  w.     S.  reddifh 
1782.    w.      Diftance    59^^    ^^"\      Politioii   36°   ^Y   f.   pre- 
ceding *. 

73.  T  Urfae  majorls.  Fl.  14.     Duarum  in  collo  praecedens. 
June  II,     Double.     Extremely  unequal.     L.  w. ;  S.  d.     Dif- 
1782.    tance  54''  46^'^     Pofition  about  45°  n.  following. 

74.  S  (Fl.  72'')  Serpentarii  borealior. 

June  16,     Double.     More  than  i  degree  n.  following  the  56th 
1782.    double  ftar  of  the  Illd  Clafs  ;  nearly  in  a  line  parallel  to 

the62dand  72d  Serpentarii,     Very  unequal.     L.  rw.  ; 

S.  r.     Di{l:ance40^'  54^^^     Pofition  39°  15^;  inaccurate. 

*  One  of  thefe  ftars,  at  leafl,  feems  to  have  changed  its  place  fince  the  time 
of  Flamsteed,  who  makes  their  difference  in  R.A,  45",  and  in  P.D,  1'  35"» 
Pofition  f.  preceding;  hence  we  have  the  hypotenufe  or  diftance  above  i'45"» 
inftead  of  59"  59'",  and  pofition  69°  46'  inftead  of  36°  57'. 

7  75- 


of  Double  Si{irs.  i  go 

V.  y^.  E  telefcGplcis  e  Coronas  borealis  fequentlbus. 

July  18,  Double.  About  i  degree  f.  following  ?,  in  a  line 
1782.  parallel  to  ^  and  t  Coronae ;  the  preceding  of  three 
forming  an  arch.  Extremely  unequal.  L.  r.  ;  S. 
darker  r.  Diftance  41''  12'''.  Polition  16"  o'f.  fol- 
lowing. 

76.  jG  i\qLiarii.  Fl.  22.     In  finiftro  humero. 

July  20,      Double.     Exceffively   unequal.     !L.  w. ;  S.  d.     Dif- 
1782.    tance   about    53''    it"^  i    very    inaccurate.       Pofition 

55°  48; 

77.  ^/(Fl.  43^)  Sagittarii  borealior  et  fequens. 

Aug.  4,       Double.     A  few  minutes  n.  following  the  43d,  in  a 
1782.    line  parallel  to  0  and  tt  Sagittarii ;  the  nearefl  of  two. 
Extremely  unequal.     L.  w. ;  S.  d.     Diftance  with  278, 
36''  ^"'.     Pofition  78°  45'  f.  following. 

78.  f  Sagittarii.  Fl.  38.     Trium  fuper  coftis  fub  axilla. 

Aug.  4,       Double.     Extremely  unequal.     L,   r.  ;  S.    d.     Dif- 
1782.    tance  VthClafs.    Pofition  28°  6' n.  preceding.   A 

third  ftar.     Diftance  about  four  times    as   f^r  as  the 

former.     Pofition  alfo  n.  preceding. 

79.  Fl.  9  ::  Caffiopeias. 

Aug.  25,     Double.     Of  two  in  a  line  parallel  to  /G  and  y,  that 
1782.    towards  y  Caffiopeiae.     Very  unequal.     L.  w. ;  S.  pr. 
Diftance  52'^  39"^'     Pofition  50°  36' n.  preceding. 

80.  T  Aquarii.  Fl.  69.     Duarum  in  dextra  tibia  borealior. 
Aug.  28,     Double.     Very  unequal.     L.  rw. ;  S.  d.     Diilancc 

1782.    36'^  ^f>     Pofition  19"  54'  f.  following. 

81.  Fl.  35  ::  Caffiopeiae.     In  finiftro  crure. 

Aug.  28,     Double.     Confiderably    unequal.     L.    rw. ;    S.    br. 
jj32.    Diftance  42'^  ^S'"*    Pofition  85°  12'  n,  following. 

82. 


1  ro  Mr.  Her  sen  el's  Catalogue 

V.  82.  V  (Fl.  25^"^)  Caffiopeiifi  prcecedens.  '  In  finiftra  manii, 
Au?-.  2S,      Double.     Near   |  decree  u.  precedino;  f,  in  a  line  Da-« 

ij82.    raliel  to  a.  and  /3  CaPiiopeia?.     Nearly  equal.     Both  pr, 
Dilrance  43''  26'''.     Poiitlon  7°  48'  n.  following. 
8j.     ip  Cadiopeiae.  Fl.  36.     Sub  pede  finiflro. 
Aug.  28,     Double.     Very  unequal.     L.   pr. ;    S.   r.     Dlftance 

1782.    2)?>'  '^S'  ' '     Politioii  10°  12'  f.  following. 

84.  Fl.  47  ::  Caffiopeiai.     Ex  obfourioribus  infra  pedes. 

Aug.  29,     Double.     The  largeft  of  three  forming  a  rectangular 
1782.    triangle  on,  or  near,  the  place  of  the  47th  CaffiopeicE.    A 

little   unequal.     L.    rw. ;     S.   pr.     Diftance  50'''  S^'"* 

Poiition  3°  33''  n.  preceding. 

85.  ^  (Fl,  27^)  borealior  et  pra^cedens.     In  dextro  brachio. 
Aug.  29,     Double.     About  |  degree  n.  preceding  a  Andromedae 

1782.    ^  verfus.     Very  unequal.     L.  rw. ;  S.  r.     Diflance  30'' 
^Y^' *     Pofition  79°  24'  n.  following. 

86.  Fl.  1 2  Urfjc  minoris. 

Sept  4,      Treble.      Extremely   unequal.     All    three    r.     The 
1782.    neareft  is  the  fmalleft.     Poiition  fome  degrees  f.  follow- 
ing.    The  fartheft  alfo  fouth,  but  more  following. 

87.  (T  Capricorni.  Fl.  7.     Sub  oculo  dextro. 

Sept.  5,      Double.     Very,  or  almoft  extremely  unequal.  L.  r. ; 
■1782.    S.  d.  bluifn.     Diflance  50^^  ^i"\     Poiition   85°   12'  f* 
.following. 

88.  ^  (Fl.  1 5^)  Aurigae  borealior.     In  finlflra  manu. 

Sept.  5,      Double.     About  3'  or  4^  n.  following  the  15th  Au- 
.5782.    rigae.     Very  unequal.     Diitance  34'^  15^^^,  mean  mea- 
fure.    Pofition  54"^  6'  f.  preceding. 


BqJ 


of  Double  Stars.  .  i  t  i 

V.   89.  5  AurigiE.  Fl.  37.     In  dextrocarpo. 
Sept.  5,      Double.     Exceflively  unequal.     L.   fine  w. ;  S   rcd- 
1782.    dllh.     Diftance    with  460,  ^^^^  iZ'^\  narrow  mcafure. 
Pofitlon  i6°o''n.  preceding.     A  third  ilar  in  view, 
po.  V  Aurigs".  Fl.  32.     In  dextri  brachii  ancone. 
Sept.  5,      Double.     Exceffively  unequal.     L.  orange  w. ;   S.  r. 
1782.    Diftance  53^^  43'^^     Polition  61''  48^  f.  preceding.     S. 
not  vitible  till  after  fome  ip.inutes  attention. 

91.  /3  (Fl.  34*)  Aurigas  adje^la.     In  dextro  humero. 

Sept.  5,      Double.     Near   \   degree  f.   following  /G,  in   a  line 
1782.    from   the  27th   continued  through /3  Auriga;  a  confi- 

derable  ftar.     Very   or  extremely  unequal.     L.  pr. ;  S. 

d.     Diftance  30^^  3^^^     Pofition  ^45°  6'  n.  preceding. 

92.  Fl.  3*  Arietis  borealior. 

Sept.  10,     Double.     Full  i  degree  f.   following  the  3d  Arietis,. 

J782.  in  a  line  parallel  to  a  Arietis  and  (JCeti ;  the  moft  fouth 
of  two.  Equal.  Both  reddifh.  Diftance  51^'  i6^^\ 
Pofition  52°  45''  n.  preceding  or  f.  following. 

93.  Fl.  103'™  Herculis  fequens  ad  auftrum. 

Sept.  ig,     Double.     About    i|  degree  f.    following   the    io3jd 

1782.    Herculis,  in  a  line  parallel  to  the  ift  and  loth  LyriE  ; 

the  neareft  of  two.     Equal,  perhaps  the  following  the 

fmalleft.     Both  r.     Diftance  47'^  46'''.     Pofition  45^ 

42'  f.  following. 

94.  Duarum  Fl.  31^""  Cephei  fequentium  auflrina.. 

Sept.  30,      Double.     About  |    degree   n.   of   the  31ft    Cephei, 
1782.    towards  ctf  Polaris.     Pretty  unequal.     Botlipr.    Diftance 
41^'  ^o"\     Pofition  45°  15^  f.  following. 

95.  Fl.  51  Aquarii.     In  dextro  cubito. 

oa.  2,       Double.     Exceffively  unequal.     L.  rw- ;  S.  d.     Dif- 
1782.    tance  Yth  Clafs.     Pofition  n.  preceding.      Two. 

other 


1 1  2  Mr.  Herschel's  Cafa/ogue 

V.  -  other  flars  in  view ;  the  neareft  of  them  extremely 
unequal.  Pofitioii  about  80  or  90°  f.  preceding.  The 
farthefl:  very  unequal.     Poiition  about  30°  f.  following, 

96.  u  (Fl.  59'™)  Aquarii  fequens  ad  auftrum. 

oa.  2,       Double.     About  |   degree  f.   following  u,  in  a  line 
1782.    parallel  to  5  and  c  iVquarii.     Extremely  unequal.     Dif- 
tance  Vth  Clafs  near.       Pofition     15   or  20°   f.   pre- 
ceding. 

97.  Fl.  10  LacertSB. 

oa.  4,       Double.     Very   unequal.     L.   w. ;  S.    r.     Diftancc 
1782.    with  278,  52''  3^^^^»     Poiition  38°  45^  n.  following. 

98.  Fl.  3  Pegafi. 

oa.  4,       Double.     Pretty  unequal.     L.  wr, ;  S.  dr.     Diftance 
1782.    34^^  43^^  •     Pofition  82°  48^  n.   preceding.     Befides  II, 
62.  another  flar  in  view,     Pofition  following. 

99.  Fl.  33  Pegafi. 

oa.  4,       Double.     Confiderably  unequal.     L.  pr. ;  S.  r.    Dif- 
1782.    tance  with   278,  45'^  3^^^.     Pofition   89°   12^  n.    fol- 
lowing. 

100.  Fl.  59  Orionis. 

oa.  4,      Double.     The   following  of  two.     Extremely  \ine- 
1782.    qual.     L.  w. ;  S.  a   point  requiring   fome  attention  to 

be  feen.     Diftance   ^y'''   i$^'\     Pofition  about  6f  f. 

preceding, 
loi.  V  (Fl.  36="")  Orionis  praEcedens. 

oa.  4,       Double.     About    |    degree  preceding  t;,  nearly  in  a 
1782,    line  parallel  to  jc  and   jS  Orionis ;  the  fecond  from  v. 

Extremely  unequal.       L.  w. ;    S.   r.      Diftance    44^'' 

15''^     Pofition  about  15°  f,  following. 


102. 


cj'  Douhk'  Stars.  '  Jj  3 

V.   102.   Pl.  61  Ccti. 

oa.  12,     Double.     Extremely  unequal.     L.  rw.  ;   S.  dr.    Dlf- 
1782.    tancc  with    278,   2>l"  S'^" '     Poiition    76'   21     i  pro- 
ceding.     A  tliird  il:ar  at  fome  diilance.     A  iictle  une- 
qual.    Pofition  n.  following. 
103-.  AI3  ;  (Fl.  18^)  Lynt*  /3  vcrfus. 

Oct.  24,     Double.     Full  \  degree  f.  preceding  /,  nearly  towards 
1782.    iG  Lyra\     Extremely  unequal.     L.  \v.  ;  S.  r.     Diilance 
with  278,   45'^  32'^'^*     Poiition  29°  12^  n.  followhig, 

104.  £  (Fl.  4*)  Sagitti-e  auftrallor  et  pra^cedens. 

Nov.  6,       Double.     Full   \  degree  f.  preceding  £,  In  a  line  pa- 
1^82.    rallel  to  y  Sagittae  and  y  Aquil« ;  the  nejireft  of  two. 

Extremely  unequal.    L.  pr.  ;  S.  d.    Diilance  Vth  Clafs. 

Pofition  16°  18'  f.  following. 

105.  y  (Fl.  14*)  Sagitta;  auftralior  et  fequens. 

Nov.  6,       Double.     About  }  degree  f.  following  y  Sagitti^e,  in  a 
1782.    line   parallel    to    Sagitta  and  Delphinus.     Confiderably 

unequal.     L.  pr. ;  S.  r.     Diilance  38^^  j6^^'.     Pofition 

74"^  15^  f.  following. 

106.  7(Fl.  12')  Saglttas  boreallor  et  praecedens. 

Nov. 6,       Double.     About  i\   degree   n.  preceding  y  Sagitta?, 
1782.    towards    the    6th    Vulpecul* ;     a    coniiderable    flar. 

Equal.     Both  rw.     Diilance  38''  54'''.     Pofition   60' 

42^  n.  preceding  or  f.  following. 

107.  Fl.  56  Aurigae. 

Nov.  6,      Double.      Confiderably    unequal.      L.    w^ ;    S.    pr. 
3782.    Diilance  52''  Si'"-     Pofition  72°  36'  n.  following. 

108.  y.  (Fl.  13^)  Canis  majoris  borealior. 

Nov.  6,      Double.     About  %  degree  n.  of  v.  Canis  majoris.     A 
1782.    little   unequal.     L.   dw. ;     S.   d.     Dilhuice  42"    S?)"* 
Pofition  23"  18'  n.  following. 
Vol.  LXXV.  Q  10;. 


114.  Mr.  HrnsciSEL^s  C^talogfdg 

V.    109.  Inter /3  Cancii  et  ^Hydrae. 

Nov.  6,      Double.     A  large  flar  not  in  Fr.AMSTEF.D,  between 
2782.    13  C.mcrl  and  0  Hydric.     Exceiiively  unequal.     Drftancc- 
35"  24 ^'^     Poiition  3  >°  o'  n.  preceding. 

I  JO.  Fl.  Ill  Tami. 

Ndv.  13,      Double,     ^'e^y    unequal.     L.    rw. ;  S.  r.     Diflance 
1782.    46'^  42  '".     Pofition  3'  48'  n.  preceding. 

111.  Fl.  42"'  Urlk  mnjorls  aufh-alior  et  i'equens. 

Nov.  20,     Double.     Full    1    degree  1.    following  tlie   42d,  in  a 
1782.    line  parallel  to   the  29th   and  48tb  Urlie  majoris ;   the 
middle  of  three  forming   an   arch.     Conliderablv  une- 
qual.    L.   wr, ;    S.  r.     Diftance    ^o'^   ^o'\     Pofitioa 
5  1°  2j^  n.  following. 

1 1 2.  *  Ex  obicurioribus  ^  and'  v  Gemrnorum  fequentibus* 

Dec.  T,       Double.      Forms  almoft  an  ifofceks  triangle  with  ^ 
1*^82.    ^nd  V  Gemlnorum.      Nearly  equal.     The   preceding  pr. 
the  follow jn 2:  wr.      Diftance  Vth  Clafs  far. 

113.  *  Fl.  9*""  itnter  et  i  i''"  Orionis, 

Dec.  7,       7Veble.      About    if    degree    f.    preceding  the    nth 
1-82.    Orionis,  tovyards  ;  Tauri.     The  two  largell;  confidera- 
bly -unequal.     L.  w.  ;  S.  pr.     Diftance  37^^  51^'^     Po- 
rtion  '2j'^  54^  n.  preceding.     The  third  farther  off  and' 
fmaller.     S.  r.     Pofition  n^  following. 

1 14.  Fl.  103  Tauri. 

Dec.  7,       Double.     Excefiively  unequal:.     L.  rw. ;   S.  d.     Dif- 
^^82.    tance  with  278  and  625,  30'^  x"\  mean  meafure.     Po- 
iition 72''  24'. 

1 15.  0  Tauri.  Fl.  i  14. 

Dec.  7,       Double.     Excefiively  unequal.     Tv.   w. ;  S.   a  point. 

r;82.    Diilance    5.'''    34'^'.     Pofition    77'    54'    f.   preceding. 

2  Two 


«/  Double  Stars,  1 1 5 

V*         Two  otiicr  fniall   liars  following,  nn<I"  a  third  to  the 

nortli. 
316.  Fl.  41  Arietis. 

Dec.  2"      Treble.     The  two  nearefl  exceflively  unequal.  T..  w.; 
1782.    S.  a   point.     Ulflance   with  278,  39''  2o''\     l\)iitioa 
So""  48'  f.  preceding.     For  the  diftance  of  tlie  tarthefc, 
lee  VI.  5.  ■*. 

117.  f  (Fl.  S^'""')  Arietispraecedens  ad  borcam. 

Dec.  2-,%     Double.     About  i|   n.  preceding  f,  towards  the  41ft 
i;S2.    Arietis;  the  following  of  four  forming  an  nrcb..     ^^ery 
unequal.     Both  dr.     Diflancc  34''  4H"'.     Pohtiou  47^ 
33^  n.  preceding. 

118.  6  (Fl.  46^)  Orionis  boreallor  et  prsceden?. 

Dec.  28,  Double.  The  mod  11.  of  three  preceding  e  Orionis, 
3782.  towards  ijl  Tauri.  More  north  is  another  let  of  three; 
care  mufl:  be  taken  not  to  miftake  one  of  tliem  for  this,. 
\  Extremely  unequal.  L.  rw.  ;  S.  d.  Diftance  Vrh 
Clafs.  Pofition  1 3"^  6^  f.  preceding.  Two  more  fol- 
lowing, exceffively  unequal;  one  about  i\  the  oth.er 
about  1 1  minute. 

119.  6  (Fl.  46')  Orionis  auftralior  et  praecedens. 

Dec.  28,     Double.     Full  |  degree  f.  preceding  g,  in   a  line  pa- 

1782.    rallel  to  e  Orionis,  and  b  Eridani ;  the  fmallefl  and  mofl; 

f.  of  two.     Very  unequal.    L.  w^. ;  S.  r.     Diftance  30^'' 

12^^^;  a  little  inaccurate.     Pofition  2 1""  33  f  preceding, 

A  third  ftar  2  or  ^°  f.  following. 

*  The  ftar  VI.  5.  in  the  plsce  referred  to  is  called  Flamsteeb's  35th 
Arietis.  With  fo  many  ftars  and  meafures  it  was  hard'y  poirible  to  avoid  ieveral 
errors,  I  have  therefore  now  added  to  the  errata  already  given  at  the  end  of  vol. 
LXXII.  and  LXXIII.  of  the  Phil,  Tranf.  fome  others,  that  have  fince  been  detetfted 
by  a  careful  review  of  the  double  ftars,  and  believe  that  no  more  will  be  found. 

0^2  120. 


1 1 6  Mr .  I  i  E  R  sc  H  E  L*' s  Calaljg  us 

V.   120.  Fr..  15  Hydiae. 
l>ec.  28,      Double.     Extremely    uiicqual.     L.  vv. ;  S.  r.     Dii- 

1782.  t;ince  43''  i^'\     Polition  about  70°  n.  preceding.. 
12!.  ^  Coma;  Berenices.  Fl.  12. 

Jan.  I,       Double.     Confiderably   unequal.      L.    rw. ;    S.    pr. 

1783.  Diibnce  S^"  5S'"*     Pofitlon  about  y;*-' f.  following. 
122.  Fl.  44^  Bootls  nuilralior  et  priiecedens. 

'r-Au  8,        Double.      Near    5    degree    i,    prect-ding    the    44tli, 
17H3.    towards  the  3Bth  Bootls.      Very  unequal.      L,  bw.  ;  S. 

pr.     Distance  -^^'^  2\''\     PolitioH  67^  6'  f.  preceding. 
J  23.  *  In  Andromt'ds  pe6lore. 

JaiT.  8,       Double.    Equal.     Both  rw.  or  pr.     Diflance  45'^  i'^'', 
i-8^.    Porition  j»2^  24'  f.  preceding.     Its  place,  as  determined 

in  1777  by  C.  Mayer,  is  J9>.  o'' 34' 33^'  in  time,  and 

29-  45"'  3'^  decHi>ation  north. 
124.  g  (Fl.  2"")  Centauri  fequens  ad  au{!rum- 
"fan.  31,     Double.     About    1 1    degree  f.  following  ^  Centauri, 
.1783.    in   a  line  parallel  to  y  Serpentis  and   ^  Centauri ;  the 

moft  f.  of  two.     Confiderably  unequal,     Diftance  54''^ 

1  '^' ;  too  low  for  accuracy. 
12 y  Fl.  46"""  Bootls  fequens  ad  boream. 

Feb.  3,       Double.     Near  2  degrees  n.  following  the 46th,  in  a 
1 78-.    line  parallel  to  J"  Bootis  a^id  Q>  Coron;£ ;  the  third  fbar 

about   that    dire«i^ion.     Confiderably   unequal.     L.    r. ; 

S.   darker   r»     Diftance  ^^^    53^     Pofition  ^7°  Z^^   ^» 

preceding. 
126.  r  (Fl.  5'"')  Herculis  pra?cedens  ad  auflrum. 
Feb.  3,       Double.     Near  |  degree  f.  preceding  r  Herculis,  In 
i-jS-^.    a  line   parallel  to  y  and   c*  Serpentis;  a  fmall  Aar.     A 

little    unequal.     Both    pr.     Diftance  '^f'  51^^^  rather 

lull  mcaltire.     Pofition  52°  6^  f.  preceding. 

127. 


of  Dovble  Stars,  i  ly 

V.  127.  (Fl.  41*"')  HltcuHs  prsecedens  ad  boream. 
Feb,  5,      Double.     About  |  degree  n.  preceding  the  41  ft  Her- 
J7S3.    culis,  in  a  Hue  parallel  to  z  Serpentarii  and  /3  Herculis. 

Pretty  unequal.     Both  r.     Diftnace  48''4o''''.     Pofirion 

19"  45'  n.  preceding. 

128,  <  (Fr..  68*'")  Virginis  iequens. 

t^eb.  7,       Double.     About    1 1     degree    following    i    Virginis, 
1783.    in  a  line  parallel  to  Spica  and  /Q  Libric.     A  little  uac« 
qual.     L.  pr. ;  S.  r.     Di{laace4i'' 58''', 

129.  /  (Fl.  25'"')  Virginis  Icqucns  ad  lx)ream. 

Feb.  7,       Double.     About   i\   degree  n.  lollowingy,  in  a  line 
1783.    parallel  to  y  and  e   Virginis;  a  large  flar.     Very  une- 
qual.    L.  r. ;  S.  dark  r.     Diftancc  46^'  42'^^     Pofitloii 
6  or  y"'  f.  following,     A   double  liar  of  the  Vth  Clafs 
In  view,  preceding. 
I  20.  Fl.  -2,^  ComiE  Berenices. 

Feb.  26,     Double.     Very    unequal.     L.    r. ;    S.    d.     DiRance 
1783.    31'''  17^''.     Pofition  36°  51^  f.  following. 

13 1 .  Fl.  24**"  Librae  fequcns  ad  boream. 

Mar.  I,       Double.     About    ri   degree  n.  following   the   24th 
1783.    Librae,  in  aline  parallel  to  tt  and  /3  Scorpii.     Confidera' 
bly  unequal.     L.  rw. ;  S.  r.     Diftance  47'^  46^^^ 

132.  Fl.  29*'"  inter  et  30'"'  Librae. 

Mar.  I,      Double.     Of  two  between  the  29th  and  30th  Librae 
1J83.    that  neareft  to  the  30th.     Very  unequal,     L»  w. ;  S.  d. 
Diftance  39''  59^^^  3  ^^^7  inaccurate. 

133.  Fl.  60  Herculis. 

Mar.  7,       Double.     Extremely  \inequaL     L.  w. ;  S.   d.     Dif- 
1783.    tauce  48'^  40'".     Poiitiou  ^f\  o'  n.  preceding. 


1 1 S  Mr,  F-Ie  R  s c  H  E I /  s  Catalogue 

V.   134.  ^  (Vl.  4"'")  Ophiuchi  priecedens  ad  auflrum. 
Mar.  24,      Double.     Abo'Jt  i  degree  preceding  and  a  little  C  of 
1783.    -^t  in  a  line  parallel  to  ^  Ophiuchi   and  w  Scorpii ;  the 

fartheft  of  two  In  the  bafe  of  a  triangle.     Equal.    Dif- 

tance  45'^  47'''- 

135.  Ad  Fl.  49*"  Camelopardali. 

April  4,      Double.     The  fmalleft  and  mofl  f.  of  two  that  arc 

1783.    about  20^  afundcr.     A  little  unequal.     Both   r.     Dif- 

tance  with  278,  38''^  1 8^"^     Pofition  85°  o'  f.  preceding. 

136.  5  (Fl.  65^)  Aquilae  borealior. 

Sept.  12,      Double.     About  f    degree  n.  of  ^,  in  a  line  parallel 
1783.    to  ?j  and  /3  Aquilae;  a  confiderable  flar.     Confiderably 
unequal.     L.  pr. ;  S.  r. ;  Diflance  with  278,  47'^  5^^^. 
Pofition  65°  48 '  f.  preceding. 

137.  X  (Fl.  17^)  Cygni  borealior. 

Sept,  22,     Double.     About  1}  degree  n.  of  %,  towards  J*  Cygni ; 
1783.    a  confiderable  flar.     Confiderably  unequal.     L.  garnet ; 
S.  r.     Diflance  with  278,  35''  i''\     Pofition  ^f  3' n. 
following. 


SIXTH    CLASS   OF    DOUBLE    STARS, 

VI.  G'],  7}  Orionls.  Fl.  28.     In  extremo  enfis  manubrio, 
Dec.  27,     Double.     Exceffively  unequal,     L.  w. ;  S.  d.     Dif-    t 
1781.    tauce  i'  50''  57''^-     Pofition  35°  12'n.  following. 

68, 


of  'Double  Stars.  j  i  p 

VI.  6S.  J]  (Fl.  28^)  Orionis  aiiftralior. 

Dec.  27,     Double.     About  \    degree  f.  of,  and  a  little  follow- 
1781.    ing  ij,  ill  a  line  nearly  parallel  to  I  and  t^  Ononis.     Very 
unequal.     L.  r.  ;  S.  d.     Dlftance  z'  o"  i\*",     PoiiUoii 
7°  54'' «.  preceding. 

69.  Fl.  :4Arietis.     Supra  caput. 

Dec.  27,     Double.     Very    unequal.     L.  pr. ;   S.   dr.     Diftance 
1781.     i'  -9^^  28^".     Polition  li'ia'  n.  preceding. 

70.  (3  Geminorum.  Fl.  70.     Supra  caput  prioris  !£'. 

Dec.  2.7,     Treble.     Or   two  fniall  flars  in  view  ;   the   nearefl:  a 

1781.  little  more  than  i  minute  ;   the  other  not  much  farther. 

71.  T  Hydrie.  Fl.  31.     Trium  inflexucolh  auftraliffima. 

Jan.  20,     Double.     Pretty  unequal.     L.   w.  inclining  to  rofe 

1782.  colour.     S.  pr.   Diilance   \'  v"  40'''.     Pofition  88"  36' 
n.  preceding. 

72.  Ad  Fl.  68'™  Orionis.     In  fufle. 

Jan.  30,      Double.      The   moil:   n.    of   two   that   are    i    degree 
1782.    ai under.     Very  unequal.      L.    \\\  ;    S.   dr.       Diftance 
with  278,    1/  iz"  $0'" ,     Pofition.  41°  o'  f  preceding. 
73..  e  Geniinorum..  Fl.  27.     In  boreali  genu  praecedentis  U^', 
Feb.  2,  1782.     Double.     L.  w.     Diilance  1^  50^^  30^^^ 

74.  Fl.  51  Geminorum. 

Feb.  2,,       Has  two  very  obfcure  flars  in  view..     L.  r. ;  S.  r.  S.  r, 
1782.    The  nea-reft  about    It,  the  next  %  minutes.     Pofition. 
of  both  about  40  or  50""  n.  following. 

75.  (w  Cancri,  Fl.  4.     Ad  primum  borealem  forficem. 

Feb.  2,       Has  a  very  obfcure  ftar  in  view.     L.  pr.     Diflance 
1782.    about  I  5  minute.     Pofition  about  30*^  n.  preceding.     A 
thij'd  about  z\     Pofition  more  north. 


76.. 


120  Mr.  Herschhi,'^  Caiahgue 

VI.  76,  ^  Leonls.  Fl.  14.. 

Feb.  2,       Double.     Extremely  unequal.     L.  r\v. ;  S.   r.     Dif« 
1782.    tance  i'  3''  29'''.     Potition  49°  36'  n.  following. 
'^7.  T  VIrginis.  Fl.  93. 
Feb.  4,       Double.     Very  unequal.     L.  w. ;    S.  dr.     Diflance 

1782.      I'8^^2  2^^^ 

78.  f  (Fl.  16'"")  Cancri  fequitur. 

Feb.  8,       Double.     About  i  degree  following  ^Cancri,  towards 
1782.    ij  Leonis.     Extremely  unequal.     Dirtance  i^  3^''47^^^. 

79.  (p  Leonis.  Fl.  74, 

Feb.  9,       Double.     V^ery  unequal.     L.  w. ;  S.  pr.     Diftance 
1782.     i'  38''  ^S^'^*     Pofition  about  10  or  12°  n.  preceding. 

80.  Fl.  ()^  Leonis. 

Feb.  9,       Double.     Very  unequal.     L.  w. ;  S.  db.     Diftance 
1782.     i^  10''  13'' . 

81 .  Fl.  27  Virginis.     In  ala  dextra. 

Feb.  9,       Double.      Extremely   unequal.      L.    w.      Diftance 
1782.    i^  28^U8^^ 

82.  Fl.  31  Monocerotis.     In  media  eauda. 

Feb.  9,  Double.     Very   unequal.     L.    rw.  ;    S.   db.     DiftanQe 
1782.     1^  10^^  ^3'^'-     Pofition  40°  o'  n.  preceding. 

83.  Prope  Fl.  i^'"  Orion  is. 

Feb.  9^       Double.     A  few  minutes  f.  following  the  ifl,  towards 
j-82.    the  belt  of  Orion.     Coniiderably  unequal.     L.  pr. ;  S. 
r.     Diflance  i'  20'^   58'"^     Poikion    88^    15'  n.   fol- 
lowing. 

84.  Fl.  14  Canis  minoris, 

Feb.  9,       Treble.     The  nearefl  extremely  unequal.     I^.  nv. ; 
i;82.    S.  d.     Diflance  i'  s"   -^'''-     Pofition   26^  24'  n.  fol- 
lowing. 


VL       lowing.     The  third  forms  an  angle,  a  little  larger  than 

a  redlangle,  with  the  other  two.     Pofitlon  f.  following. 

^^.  Fl.  27  Hydras. 

Feb.  9.       Double.     Very  unequal.     L.  rw. ;  S.  pr.     Dlftance 
1782.    Vlth  Clafs  far.     Polition  about  60®  f.  preceding. 

86.  Prima  ad  0- Cancri.  Fl.  51. 

March  5,      Double.     Extremely  unequal.     L.  w. ;  S.  d.     Pofi* 
1782.    tion  n.  following. 

87.  Tertia  ad  0- Cancri.  Fl.  64.  . 

March  5,     Double.     Very  unequal.     L.  rw. ;  S.  dr.     Diftance 
1782.     i'  25^^  as"'*     Pofition  25°  12^  n.  preceding. 

88.  /3  Aurigae.  Fl.  34.     In  dextro  humero. 

March  5,     Double.     Extremely  or  exceffively  unequal.     L.  fine 
1782.    bluifliw. ;  S.  d.     Diflance  z'  49''   (i"\     Pofitlon  54* 
I  z'  n.  following.     A  third  farther  off.     Very  unequaL 
About  40  or  50°  n.  following. 

89.  Fl.  6*  Bootis  adje6ta. 

Mar.  12,      Double.     Juft  following  tlie   6th  Bootis.     A  little 
1782.    unequal.     L.  r. ;  S.  deeper  r.     Diftance   i'   19^^  y)'"^ 
Pofition  58°  6^  f.  preceding. 

90.  Fl.  61  Virginis. 

Apr.  3,      Double.     Very  unequal.     L.  w. ;  S.   d.     Dlilan«e 
1782.    i'  13"'  I5^^'«     Pofition  about  ']^''  n.  preceding. 

91.  Prope  y  (Fl.  24^"")  Geminorum. 

Apr.  15,     Double.     Three  or  four  minutes  n.  of  y  Geminorum. 
1782.    Confiderably  unequal.     Both   fmall;    too  obfcure  for 
meafures  with  7 -feet;  my  20-feet  fhews  a  third  flar 
'between  them  with  12  inches  aperture, 

Vgl.LXXV*  R  92^ 


122  Mr.  Herschel's  Catalogue 

VI.  92.  <^  (Fl.  i^)  Capricorni  borealior. 

June  14,     Double.     About  J  degree  n.  of  J  Capricorni.     Very 
1782.    unequal.     Both   r.      Diftance    i'    2.'^    \6^'\     Pofition 
2°  3^  f.  preceding. 

93.  0  Coronae  borealls.  Fl.  15.     Ad  fummum. 

July  J 8,     Double.     Very  unequal.     L.   w. ;    S.    d,     Diftance 
1782.    i'  27^^44''^';  a  little  inaccurate.     Pofition  54°  27'  f. 
following. 

94.  A  Corona  borealis.  Fl.  12. 

July  18,     Double.     Extremely   unequal.     L.  w. ;  S.  r.     Dif- 
1782.    tance  1^35'^  i^'^\     Pofition  33^  12^  n.  following. 
pj.  72  Bootis.  Fl.  8.     Trium  in  (iniftro  crure  borea. 
-Aug.  3,       Double.     Extremely    unequal.     L.   w.  inclining  to 
1732.    orange;    S.   r.     Diftance   about   if   minute.     Pofition 
about  25  or  30*^  f.  following.  ^ 

96.  f  Perfei.  Fl.  44.     In  pede  finiflro. 

Aug.  25,     Treble.     The  nearefl  extremely  unequal.     L.   w.  ; 

1782.  S.  r.  Diftance  1'  ii^''  2b''\  Pofition  66°  36'  f.  pre- 
ceding. The  fartheft  very  unequal.  S.  r.  about  if 
minute.     70  or  75°  f.  preceding. 

97.  Secunda  ad  t  i^quarii.  Fl.  71.     In  dextro  eruie.. 
Aug.  28,     Double.     Very  unequal.      L.    r. ;    S.   d.     Diftance 

1782.  2'  3^^  36^^%  mean  meafure*  Pofition  18^  30''  n.  pre- 
ceding. 

98.  Fl.  46''"  Tauri  fequens  ad  auftrum. 
Sept.  7,      Double.     About    i|   degree  f.    following  the  46th,. 
iy82.    nearly  in  a  line  parallel  to  the  38th  Tauri  and  the  42d 

Eridani.     A  little  unequal.     L.  pr. ;    S.   r.     Diftance 
Pofition  43°  48^  n.  preceding.     A  double 


r  2 


//  ^  /// 


ftar  of  the  Vth  Clafs  in  view,  following  within  ^\ 

Equal, 


of  Double  Stays.  1 2  j 

VI.        Equal.     Both  fmali  and  r.     Almofl  ftmilarly  fituatcd 

with  the  above,  but  politioii  more  n.  preceding* 
^g,  m  Perfei.  Fl.  57.     In  dextri  pedis  talo, 
Sept.  7,      Double.     Pretty  unequal.     [>.  r. ;  S.  rw.     Diftancc 
1782.     i^  3^"  ^Y^^*     Pofition  71°  51^  f.  preceding. 
100.  /  (Fl.  32^'")Cephei  fequens. 

Sept.  30,     Double.     About    i|    degree  n.    followiiig    i,   nearly 
1782.    towards  y  Cephei.     A  little  unequal.     Both  pr.     Dif- 

tance  i'  i^^  54^^''*     Pofition  8°  9'  a.  preceding. 
loi.  I  Tauri.  Fl.  68. 

oa.  31,     Has  two  ftars  in  view.     The  neareft  exceffively  une- 

1782.    qual.     L.  w. ;  S.  d.     Diftance  with  278,   i'  2,'^  i8''^ 

Polition  35°  24'  f.  preceding.     The  fartheft  extremely 

unequal.     S.  r.     About  i  {  minute.     Pofition  about  50'^ 

n.  preceding. 

102.  Fl.  5  Lyncis. 

Nov.  13,     Double.     The   largeft   of   a   fmall  triangle.      Very 
,782.    unequal.     L.   r. ;    S.  garnet.     Diftance    1^   28''  20''^ 
Pofition  2°  o'  n.  preceding. 

103.  ePegafi.  Fl.  8. 

Nov.  20,     Double.     Very  unequal.     L.  pr. ;  S.  dr.     Diftance 
1782.    i'  30'^  S^'^'     Position  52°  45^  n.  preceding. 

104.  ^Bootis.  Fl.  30.     In  dextro calcaneo. 

Nov.  29,     Has  a  very  obfcure  ftar  in  view.     Extremely  unequal. 
1782.    L.  w.  inclining  to  r. ;  S.  d.     Diftance  about  1 1  miiiute. 
Pofition  almoft  diredly  preceding. 

105.  Fl.  105  Tauri. 

Dec.  7,      Double.     Very  unequal.     L.  pr. ;    S.   r.     Diftance 
1782,    1'  41'^  Z()''\     Pofition  18°  o'  f.  preceding, 

R  2  J  06. 


fi'4  ^^^-  Herschel's  Catalogue 

\'L    loC.  b  Eridani.  Fl.  62. 

Dec.  7,       Double.       Connderably    unequal.       L.  w. ;    S.   pr^ 
1782.    Diftaiice  i^  o^' 26'^'.     Poiitlon  1 5"  9^  n.  following. 
107.  Fl.  31^  Monocerotis  aufrralior  et  prircedens. 
Dec.  21,     Double.     About   i|  degree  f.  of,   and  a  little  pre-- 
1782.    ceding  the  3 1  il  Monocerotis,  in  a  line  parallel  to  ^  Hy- 
dr;£  and  the  311I  Monocerotis ;  the  moft  fouth  of  two.- 
Confiderably  unequal.     L.  r.  ;  S.  deeper  r.     Di^auce 
about  1 1  minute.     Poiition  50  or  60°  £  following. 
P08.   5  (Fl.  22^)Hydri£  borealior  et  praecedens. 
Dec.  20,     Double.     About   |   degree    n.  of,  and   a   little  pre*- 
2782.    ceding  5,  nearly  in  a  line  parallel  to  «  and  ^  Hydras.- 
Very  unequal.     L,   r. ;  S.  blackifli  r.     Vlth  Clafs  far. 
Polition  I  or  2°  n.  preceding.     A  third  flar  preceding. 

109.  Fl.  22  an  26  Cancriincertum. 

Dec.  29,     Double.     One  of  the  two  being  loft  *,   it  does  not 
■1782.    appear  which   is  the   remaining  ftarr      Very  unequal. 
L.  r. ;  S.  dr, 

1 10.  Telefcopica  ad  0  Ceti. 

Jan.  2,       Double.     Looking  for  0  Ceti,  which  was  invifible  to 
1783.    the  naked  eye,  I  miftook  this  for  it.     Pretty  unequal. 
L.  rw.  of  about  the  eighth  magnitude  ;  S,  r.     Diftance 
1^20'^  S^''\     PofitIon33°42^ 
Ti  I.  a  Hydrse.  Fl.  30.     Duarum  contigtiafrum  lucldior. 
Jan.  8,       Has  two  ftars  within  about  2  minutes ;  the  neareft" 
1783.    exceffively  unequal;    the  farthefl  extremely  unequal. 

Both  f.  foUawing. 
112.  Fl.  13  Bootis. 

Jnn.  8,       Double.     Extremely  unequal.     L.  t.  ;  S.  dr.     Dif- 
J783.    tance  i'  17^^58^'^     Pofition  7^24^  n.  preceding. 

»  See  Phil.  Tranf.  vol.  LXXIII,  p.  252,-^ 

115. 


of  DQuble  Stars,-  ^-i^ 

VI.    113.  Fl.  4  Virginis. 

Jan.  8.       Double.     Extremely  uneqml.     L.  wr.  ;  S.  dr..    Dif-- 
1783.    tance  z'  z^"  44''^;  too  obfeure  for  accuracy. 

1 14.  Fl.  d^"'^  Orionis  priccedens  ad  auftrum. 

Jan.  9,       Double.     About    i    degree    f.    preceding,  trhe    69th, 
1783.    nearly  towards  A  Orionis.     Confiderably  unequal.     L. 

pr. ;  S.  d.     Diftance   i'  o^o"  38'''.     Polition  22"^  W  f. 

following. 

115.  Fl.  2 1 '■" Crateris  fequens  ad  auftrum. 

Jan.  10,      Double.     About   z\  degree  f.  following  the  21  fl,  in 
1783.    aline  parallel  to  the  12th  Crateris  and  4th  Corvi.    Very 
unequal.     L.  w.  ;  S.  r.     Pofition  12°  12' n.  following. 
i  16.  Fl.  43  Herculis. 

Jan.  Id,      Double.      Very  unequal.     L.   inclining  to  garnet  ;'■ 
3783.    S.  r.     Dlftance  \'   i^"  37'''.     Polition  38*^  48' f,  pre- 
ceding, 

1 1 7.  Fl.  12^  Librae  borealior  et  priscedens^ 

Jan.  10,      Double.     x'\bout    i^    degree   n.   preceding  the   12th 
178-^.    Libras,  towards  Spica.     Very  unequal.     L.  rw. ;_  S.  r. 
Pofition  about  40°  f.  preceding, 

118.  Fl.  30  Monocerotis. 

(Feb.  I",     Double.      Very  or    extremely   unequal.      Diftance 

II o.  e  (Fl.  18')  Plfcis  auftnni  auftralior  et  praecedens. 

July  28,      Double.     About    i|   degree  f.  of,  and  a  little  pre- 

578".    ceding  £  Pifcis  auflrini,  in  a  line  fromJ*  Aquarii  continued 

*  On  account  of  the  change  In  the  magnitudes  of  the  ifl:  and  2d  Hydr^e,  this 
fmall  ftar  may  be  of  ufe  to  afcertain  whether  the  30th  Monocerotis,  which  is 
fituated  between  them,  has  any  confiderable  proper  motion.  See  Phil.  Tranf.  voL 
LXXllI.  p.  255. 

through 


1 2  6  Mr.  H  E  R  ^.  c  1 1 R  t/s  Calakgue  of  Double  Stars , 

through  e  Pifcis.     Pretty   unequal.     Iv.  dpr.     S.  dr. 
Dlftance  i'  26''  58''".     Pofitlou  6f  46^  f.  following. 

120.  Fl.  43""  Saglttarii  fequeiis  ad  auftrum. 

Aug.  16,     Double.     Near  i   degree  f.  following  the  43d,  in  a 
1783.    line  parallel  to  |  and  0  Sagittarii ;  a  confiderable  flar. 

Very  unequal.     Both  dr.     Diftance  with   278,   l''   14'' 

^''\     Pofition  2"^°  o^  n.  preceding. 

121.  Fl.  1  2  Lacertje. 

Aug.  18,     Double.     Very   unequal.     L.   w. ;    S.   r.     Diftance 
1783.    with  278,   1^0"  io^^\     Pofition  73°  o'  n.  following. 


Add  the  following  errata  of  the  Catalogue  of  Double  Stars  in 
vol.  LXXII.  to  thofe  already  noticed  at  the  end  of  the 
LXXIId  and  LXXIIId  volumes. 


page. 

Line. 

For 

Read                            J 

133 

22 

25- 

25*. 

140 

0 
J 

19"  14'" 

19"  26'" 

H5 

26 

35"  48'" 

36"  9- 

^S3 

7 

V  Capricorni.  Fl.  10, 

f  Capricorni.  Fl.  ii. 

153 

II 

33°  4a' 

61-^23' 

156 

4 

Fl.  5. 

Fl.  4. 

r/,//,^./;„„.,:  I  ■„/.  L  xxir  Taij.  V.  p.iif,. 


lili 


* 


[     '27    ] 


VII.  Obfervatio?2S  of  a  fiew  variable  Star,  In  a  Letter  from 
Edward  Pigott,  Efq.  to  Sir  H.  C.  Euglefield,  Bart.F.  R,  S, 
and  j^,  S. 


Read  December  23,  1784. 


D  E  A  R     s  I  R, 

FOR  fome  years  pad  1  have  been  employed  in  verifying 
all  the  flars  fufpeOed  to  be  variable,  in  order  that  here- 
after we  may  know  with  certainty  what  to  depend  upon.  This 
undertaking,  which  is  nearly  completed,  has  already  proved 
of  ufe  in  detecting  many  miftakes,  and  producing  fome  difco- 
veries ;  among  which,  the  following  is  one  of  the  mofl:  im- 
portant. September  10,  1784,  I  flril:  perceived  a  change  in 
the  brightnefs  of  the  ftar  vj  Antinoi,  and  by  a  feries  of  obfer- 
vations  made  ever  fince,  I  find  it  lubjed:  to  a  variation  very 
limilar  to  that  of  Algol,  though  not  exadlly  the  fame  in  any 
one  particular. 

7]  Antinoi,  when  brightefl:,  is  of  the  third  or  fourth  magni-^ 
tude,  being  between  S  and  (3  Aquilas ;  and  at  its  leaft  bright- 
nefs of  the  fourth  or  fifth  magnitude,  it  then  being  betweea 
that  of  I  Antinoi  and  ^  Aquilae ;  therefore,  its  greatefl  varia- 
tion in  brightnefs  may  be  called  about  one  magnitude ;  and  the 
changes  it  undergoes,  though  probably  not  nicely  afcertained 
from  fo  few.obfervations,  are  nearly  thefe :, 

4  At 


12^  Mr.'9iGorr\Obfervatlons 

At  Its  greated  brightnefs         44  =t  hours. 

In  decreafins:         -         -  62  dr  hours. 

At  its  leafl  brightnefs  30  ±  hours. 

In  increaiing         -         -  S^  —  ^^o^^s. 

All  thefe  changes,  which  hitherto  feem  to  be  regular  and  con- 
flant,  are  performed  in  7  days  4  hours  38 — minutes;  this  Ifhali 
il:ile  its  period,  and  hereafter  will  fhew  how  it  is  determined 
with  fuch  exa6lnefs. 

The  ftars  to  which  ^  Antinoi  was  Compared  are  in  order 
thus :  ^  Aquil^e  third  magnitude,  /3  Aquilas  and  5  Serpentis 
fourth  magnitudes,  i  Antinoi  fourth  or  f  fth  magnitude,  and  ^, 
Aquilas  a  bright  fifth.  I  find,  by  feveral  years  obfervation, 
that  /3  Aqullas  retains  the  fame  brightnefs.  ;  Antinoi,  which 
has  been  examined  with  particular  attention  by  Mr.  Good- 
rick  e  and  myfelf,  is  fufpe(£ted  by  us  both  to  be  fubject  to  ar 
fmall  variation,  but  not  fufficiently  appar^ent,  fo  as  to  afted: 
materially  thefe  comparilons,  and  poffibly  it  may  be  only  the 
effedt  of  fome  optical  iliuiion  ;  for  I  have  frequently  remarked, 
that  both  in  the  twilight  and  moon- light,  or  when  the  air  is  in 
the  leafl  hazy,  there  is  a  greater  difference  between  the  bright- 
nefs of  many  of  the  ilars,  than  in  a  dark  night  and  clear  fky. 
In  the  following  journal  of  obfervations  of  17  Antinoi,  the 
Greek  letters  /3,  ^,  jt*,  belong  to  Aquila,  and  ;,  v,  to  Antinous ; 
fecondly,  the  magnitudes  marked  in  column  the  third  are  by 
eflimation,  and  can  be  of  no  further  ufe  than  merely  to  give, 
at  firft  fight,  an  idea  of  the  ftar's  brightnefs ;  and  laftly,  the 
lines  diftinguifhed  by  inverted  commas,  are  extra«5ts  from  Mr, 
Goodricke's  journal,  whofe  friendly  afliflance  I  have  often  ex* 
perienced,  and  was  the  more  welcome  on  this  occafion,  becaufe 
repeated  attention  and  great  exadnefs  were  requifite, 

K  Dates. 


bf  a  new  Variable  Star, 


129 


Dates. 

1783- 


July  17 

27 

1784 
Sept.  10 
12 


43 
15 

>  :;j:  i. 

20 

23 

28  1 
^29  J 

30 

oa.  I 
2 


5 

6 


■r* 


8 


10 
II 

16 


Hours. 


lOd: 
IO:±: 


lOdi 

71 

Uf} 

8 
8 


Magni- 
tude, 


71 


8 


m 


9± 
9± 

I9    J 
8 

8 

8 

9^ 

8± 

8± 

8± 
8.-± 

loi 
10 
8dt 
8 


3  -4 

4 
4 


4 
4 


4 
4 


3 
3 


4 
4 
3 
3 

3 

3 


4 

4 
4 


5 
5 

4 

4 

5 
5 
5 

4 
4 


5 

5 

4 
4 

4 

4 


Journal  of  the  comparative  brightnefa  of  1  Atitinoi. 


4 
4 
4 
4 


Vgl.  LXXV, 


r  Lefs  than  J  Aquilx   and  brighter  than  6  Scipentis  (Ji 
I    Aquila;  and  S  Serpentis  are  cqxial)  weather  hazy. 
P.ather  brighter  than  ^  Aquilse  and  fi  Serpentis. 
If  any  difterence,  lefs  than  (3  Aquilre. 

N.  B.  Thefe  times  are  from  recoUefiion,  and  cannot 
err  more  than  i|  hour. 
Lefs  than  /3  Aquilce  and  0  Serpentis. 
iVluch  lefs  than  /?,  equal  to  1. 
*'  A  little  brighter  than  1,  air  clear," 

Lefs  than  ^,  brighter  than  /3,  and  much  brighter  than  p 

'*  Brighter  than  t  and  $." 

Rather  brighter  than  /3,  and  much  brighter  than  s, 

'*  Lefs  than  &  and»." 

Much  lefs  than  /3,  and  equal  to  u 

<' Lefs  than ^ and.." 

f  Brighter  than  |3  and  »;  at    1 1  h.  it  fcemed  to  have 
I       increafed. 

J  Lefs  than  ^,  rather  brighter than^ji  thought  it  rather 
1      lefs  at  ii|h.;   moon  near. 

Brighter  than  /3  ;  moon-light. 

If  any  difference,  rather  brighter  than  /?. 
"  Rather  brighter  than  ^." 

Lefs  than  i3,  brighter  than»;  air  clear,  moon-light. 

Equal  to  1,  much  lefs  than /3, 
"  Lefs  than  u" 

Between  the  brightncfs  of  ^  and  J* 
"  Brighter  than  ^  and  »." 

Rather  brighter  than  jg, 

"  Much  the  fame  as  yefterday." 

Brighter  than  » ;  think  it  not  lefs  than  /3  ;  this  obfer- 
vation  doubtful,  occafioned  by  intervening  clouds. 
"  Believe  it  lefs  than  »;  weather  bad." 
*' Certainly  lefs  than /3;  weather  bad,'  £>< 

"  Lefs  than  » ;  rather  a  doubtful  obfeivation." 
Rather  lefs  than  (3,  and  brighter  than ».  1 

Equal  to  ^. 

"  Rather  brighter  than  /3.'* 
Lefs  than  |S,  brighter  than  % 

S    .  Dates. 


l^O 


Dates. 

1784 


Hours. 


06t.  16 

18 

19 

20 

22 
23 

^       24 


25 
26 


27 


3^ 

Nov.  3 

6 


J2 


I>^ec, 


16 


17 
*9 


20 
21 

4 


H 


/  7 
18 

8 


61 

71 
8± 

6| 
8 


I  H  \ 
I7   J 

6| 
6| 

9i 


6i 

8| 

51 

H 

9 

71 

k 

{?} 

7 

5l 
8 

7 

5il 
7iJ 
6 

8 


6| 


61 


Magni 
lude. 


Mr.  Pigott's  Obfervations 

Journal  continued. 


4 

4 

4 
4 
3 

3 


4 
4 


4 
4 
4 


4 
4 


r  3 

4 
4 
3 
3 
3 

4 


4 

4 

4 

4 
4 


5 

5 
4 

4 
4 


4 

.4 


5 
5 

.4 
4 
4 

5 

5 


4.v3 


5  "  Lels  than  B  and  *." 

5  Undoubtedly  lefs  than  1. 

Lefs  than  »,  brighter  than  /^  . 

"Lefs  than.." 

Evidently  brighter  than  /3. 

"  Much  brighter  than/S.'* 

"  Brighter  than  ^." 

Lefs  than  |3. 

"  Not  fo  bright  as  ^,  brighter  than  »." 

Equal  to  »,   much  lefs  than  j3 ;  moon-light,  air  clear. 

f  "  Lefs  than.  •  5  rather,  though  very  little,  brighter 

1       thanju." 

Much  lefs  than  ^,  equal  to  »,  brighter  than  /*. 
Sometimes  feemed  rather  lefs,  but  generally  equal  toj3; 
Equal,  if  not  rather  brighter  than  Q, 

/  "  At  6|  rather  lefs,  at  8|  nearly  equal,  and  at  9I 

L      "  rather  brighter  than  ^.'*. 

r  Remarkably  bright,  nearer  5  than  /3;  moon-light, 

1    •  air  clear. 

"  Nearer  to  /S  than  to  J." 

Seemed  equal  to  ^  ;  air  not  very  clear, 

"  Rather  brighter  than  &" 

Evidently  lefs  than  &. 

Much  lefs  than /3, 

"  Lefs  than /I  and  *."" 

Brighter  than  |S,  much  lefs  than  ^. 

Rather  brighter  than  ^,  certainly  equal,  -  ■* 

"  Rather  brighter  than^  and  «." 

Lefs  than/3,  equal  to  •, 

"  Lefs  than  /3,  and  rather  lefs  than  h" 

I  Evidently  lefs  than  ^,  and  rather  brighter  than  «j   at- 

I       8' it  feemed  increafed,  and  about 
Between  its  leafi:  and  full  brightnefs. 
"  Lefs  than  |3,  and  fomething  lefs  than£.'* 

Brighter  than  ;S. 

if  any  difference,  rather  brighter  than  ^ ;  clouds   cov- 
J  ered  the  moon:    at  8h.if  any  difference  rather;  lefs- 
(  than  ^;  moon-light,  and  air  not  fo  clear  as  at  6. 

"  Rather  brighter  than  (3,.  brighter  than  i." 

Rather  lefs  than  (3,  brighter  than  ,. 

Lefs  than  |3,   rather  brighter  than  13   moon-light. 

"  Brighter  than /3." 

[f  \ny  diflerence,  lefs  than  /3, 


Ili   \ 


of  a  new  Variable  Sta}\-^\  i^^  r 

■In  order  to  obtain  a  point  of  comparifon,  for  fettling  the 
periodical  changes  of  tj  Antinoi,  which  I  fuppofe  to  be  con- 
ftant,  it  is  natural  to  fix  upon  that  phafis,  which  can  be  deter- 
mined with  the  greatefl  precifion  ;  and  this  feems  to  be  at  the 
time  when  it  is  between  its  leaft  and  greateft  brightnefs,  as 
clmoji  the  whole  increafe  of  brightnefs  is  completed  in  lefs  than 
24  hours,  though  the  perfect  completion  is  performed  only  in 
n^d  ±L  hours  ;  thus  having  fettled  this  neceffary  point,  and  found 
roughly  the  length  of  a  lingle  period,  the  computations,  in 
order  to  obtain  greater  exadlnefs,  areas  follows. 


S  s  Ti 


ime 


122 


Mr.  PiGOTT^s  Ohfervaiions 


Time    when    »,    Antlnoi   was 
between  ifs  leaft  and  greateft 
brightnefs. 

Intervals  between 
the  obfervations. 

Number  of  pe- 
riods in  ditto. 

Len 
fingl 

gth  of  a 
e  period. 

Hours. 

J 784, Sept.  12.  at  20  1 
Oa.  II.  at  11  J 

Days.  Hours. 

28    15 

4  each  of 

pays 

7 

.  Hours. 

0* 

Sept.  12.  at  20  1 
0(5t.  18.  at  20  J, 

36     0 

5     I^° 

7 

41 -^ 

Sept.  1 2.  at  20  1 
OQi.  26.  at  00  J 

■ 

43'      4 

6     D* 

7 

41  - 

Sept.  12.  at  20  1 
Nov.  16.  at    8  J 

64     12 

9     D^ 

7 

4 

Sept.  19.  at  20  -\ 
Odl.  18.  at  20  J 

29       0 

4     D^ 

7 

6 

Sept.  19.  at  20  1 
0£l.  26.  at  00  J 

3^       4 

5     D^ 

7 

5i+:' 

Sept.  19.  at  20  1 
Nov.  1 6.  at    8  J 

S7     12 

8     D^ 

7 

41 

Od.  II .  at  II  •) 
Nov.  16.  at    8  J 

3S     2r 

5     D° 

7 

41- 

oa.  18.  at  20  1 
Nov.  1 6.  at    8  J 

28     12 
ingle  period,  ( 

4     D" 

XI  a  mean, 

m 

7 

3 

I  .ength  of  a  f 

7 

4  30 

Perhaps  other  aflronomers  may  not  exadly  agree  with  me, 

in  fixing  the  times  as  fet  down  in  column  the  firft ;  for  my 

part,  I  determined   them  without  paying  any  regard  to  the 

refults,  by  taking  a  medium  between  the  times  when  n  Antinoi 

4  had 


oj  a  new  Variable  Sfat\  i  -^  j 

had  rather  pnflecl  its  lead  brightnefs,  being  nearly  equal  to  i  An- 
tlnoi,  and  when  it  was  a  little,  but  undoubtedly,  brighter 
than  jQ  Aquilas.  I'hough  it  does  not  appear,  as  I  have  already 
faid,  that  any  of  the  other  phafes  can  be  fettled  with  equal 
preclfion,  different  comparifons  neverthelefs  may  prove  fatif- 
fa61:ory  towards  corroborating  t^e  above ;  I  have  therefore  alfo 
deduced  its  period  from  the  beft  and  moft  diftant  obfervations^ 
made  when  at  its  leafl  brightnefs;  they  are  thus:  7  days 
o  hours  and  7  days  5  hours.  Thefe  refults  I  reject,  and  retain 
the  mean  given  by  the  flrfl:  fet,  with  which  we  may  proceed  on 
to  gain  a  much  greater  exaulnefs ;  let  one  period  be  lubtra^ted 
from  the  obfervation  of  July  27th,  1783,  and  it  will  appear^ 
that  17  Antinoi  had  varied  in  brightnefs  during  the  following 
four  daySy  though  at  that  time  it  did  not  ftrike  me. 

July  17th,  decidedly  brighter  than  /3  Aquilae. 

—  1  8th,  not  obferved. 

1783,    "J    —   19th,  rather  brighter  than  ,G  Aquilas. 

—  20th  (anfwering  to   the  2  7tii)   equal  or  rather 
lefs  than  jG  A  qui  lie. 

As  it  is  therefore  evident,  that  on  July  19th  and  27th,  1783, 
7]  Antinoi  was  decreafing  in  brightnefs,  I  fhall  compare  thole 
days  obfervations  to  correfponding  ones  made  in  1784, 

Hours, 

i784,Sept.  30.  at    61 

Oa.     7.  at  i6j    .    . 

0£t    k:  at    A I  Similar   obfervatrons  to   that    of    1783. 

Oa.  22.  at  lif   J^^^^  ^^th,  at  10  h.  ±,  7;  Antinoi  being 
Nov.  12.  at    2I    "^^^^^  brighter  than  /3  Aqujlae.. 


Nov.  I  p.  at  00 


17^4: 


1^4  ^^^''  Pigott's  Obfervatrons 

Hours. 

1^84,  Sept.  30.  at  18  "j 

061.   15.  at  14  i  Similar  Obfervations  to  .that   of   178^^ 
0£l.  22.  at  19  /-   July  27th,  at  10  h,  rt,  ^  Antinoi  being 


Nov.  12.  at 

14' 

equal  to  or 

rather  lefs  than  /3  Aquilae. 

Nov.  19.  at  14. 

• 

Ill  eftimating  the 

;  above   times,  I 

paid  much  attention  to  the 

obfervations  of  the  preceding  and 

following  days ;  however,  a 

few  hours  more  or  lefs  do  not  make  a  material  difference,     Tho 

I'efults  of  thefe  comparifonsare 

r 

D. 

H. 

M. 

7 

4 

39i 

7 

4 

44i 

7 

4 

53^ 

■", 

7 

4 

541 

7 

4 

32 

7 

4 

261 

7 

4 

32 

7 

4 

42i 

7 

4 

43 -V 

7 

4 

26 

7 

4 

2l| 

On  a  mean     7 

4 

38  -  length  of  a  lingle  period. 

As  this  approaches  the  mofl  to  the  preceding  refult,  It  may  be 
aiTumed  as  neareft  the  truth,  provided  the  changes  be  uni- 
formly periodical. 

Hitherto  the  opinion  of  aftronomers  concerning  the  changes 
of  Algol's  light  feem  to  be  very  unfettled ;  at  leaft  none  are 
univerfally  adopted,  though  various  are  the  hypothefes  to 
account  for  it ;  fuch,  as  fuppofing  the  ftar  of  fome  other  than 

a  fpherical 


of  a  new  Variable  Star,  i  or 

a  fpherical  form,  or  a  large  body  revolving  round  It,  or  with 
feveral  dark  fpots  or  fmall  bright  ones  on  its  furface,  alio  giv- 
ing an  inclination  to  its  axis,  &;c.  ;  though  moil:  of  thefe  con- 
jectures with  regard  to  Algol  be  attended  with  difficulties,  fome 
of  them  combined  do,  I  think,  account  for  the  variation  of 
yi  Antinoi. 

Thofe  perfons  who  are  accuftomedto  examine  the  flars  atten- 
tively will  not  befurprifed  to  find,  that  Mr.  Goodricke  and  I 
do  not  always  perfe(5lly  agree  in  our  obfervations  ;  thefe  fmall 
differences  in  the  magnitudes  of  the  flars  are  very  difficult  to  be 
afcertained  with  the  naked  eye,  which  has  often  made  me  la- 
ment, .we  had  not  fome  contrivance  for  determining  their  relative 
brightnefs,  and  even  I  attempted  feveral  methods,  but  did  nor 
purfue  them  with  fufficient  attention  and  diligence  to  obtain 
any  fatlsfa£l:ory  refults  ;  neverthelefs  I  fhall  juft  mention  them., 
as  perhaps  fomebody  elfe  may  overcome  thofe  difficulties, 
which  to  me  appeared  fo  very  confiderable. 

1.  In  177S  I  had  fmall  pieces  of  fine  glafi  ftained  with  dif- 
ferent (hades,  which  being  applied  to  the  eye  end  of  a  telefcope, 
I  could  eafily  find  what  degree  of  fhade  was  requifite  to  efface 
flars  of  different  brightnefs  \  and  thus  I  obferved  fome  of  the 
ftars  and  planets. 

2.  Diaphragms  were  attempted ;  but,  befides  other  diffi- 
culties, they  did  not  efface  flars  of  the  firfl  magnitude. 

3.  A  method  which  pleafed  me  much,  and  perhaps  may  not 
prove  unfuccefsful,  is,  by  putting  the  flars  out  of  the  focus  of 
a  telefcope  till  they  become  invifible ;  this  is  performed  by 
drawing  the  eye-tube  of  a  refra6lor either  in  or  out;  the  point 
of  focal  diflance  being  previoufly  determined,  the  brighter  the 
ftar  the  greater  length  of  tube  mud  be  (lid  either  in  or  out  to 
efface  it ;  thus  I   was  in  hopes  of  determining   their  magni- 

z  tudes^ 


136  A/>.  PiGOTT*s  Ohjervations^  &:c. 

tudes,  and  for  that  purpofe  had  in  1776  divifions  engraved  on 
the  eye-  tube  of  a  refraftor ;  but  found  tliat  its  high  magnify- 
ing powers  prevented  ftars  of  the  firfl  and  fccond  magnitude 
becoming  invifible. 

Laflly,  I  am  inchned  to  think  the  following  method  pradi«» 
cable,  vi%.  to  refle£l  in  a  telefcope,  by  means  of  an  illumina- 
tor, different  degrees  of  light  in  a  known  proportion,  fo  that 
ftars  of  all  magnitudes  may  be  obliterated. 

The  changeable  ftate  of  the  weather  will  perhaps  be  thought 
a  confiderable  obftacle  to  thefe  contrivances,  and  to  throw  doubt' 
•on  the  obfervations ;  but  this  may  be  fufficiently  obviated  by 
attending  to  fmall  telefcopic  ftars,  which  according  to  the 
clearnefs  of  the  atmofphere  are  more  or  lefs  diftinftly  feen. 

I  beg  the  favour  of  you,  dear  Sir,  to  prefent  thefe  obferva- 
tions to  the  Royal  Society ;  and  believe  me,  with  the  greatefl 
regard,  &c. 

York,  Dec.  5,  1784.  EDWARD  PIGOTT. 


[     '37     3 


VI I  r.    Ajlronomical  Obfervations,      In   iwO  Letters  from   M. 
Francis  de  Zach,  Profeffbr   of  Mathematics,  and  Member   of 
the  Royal  Academies  of  Sciences  at  Marfeilles,   Dijon,   and 
Lyons,  to  Mr.  Tiberius  Cavallo,  F.  R,  S. 


Read  December  23,  1784.  . 

SIR,  Lyons,  ApfH  4,    lySj.' 

1SEND  you  the  account  of  the  obfervations  on  the  eclipfc 
of  the  moon,  which  I  have  made  together  with  the  rev. 
Father  le  Fevre,  Aftronomer  at  Lyons,  in  the  Obfervatory 
called  au  grand  College  i  to  which  I  fliall  add  the  obfervations  of 
the  vernal  equinox  ;  fome  obfervations  on  Jupiter's  fatellites, 
made  at  Marfeilles  by  M.  Saint  JacoLJEs  de  Sylvabelle  ; 
and,  laftly,  a  new  fblution  of  a  problem  that  occurs  in  com- 
puting the  orbits  of  comets.     If  you  think  that  thefe  obferva- 
tions do  in  any  way  deferve  the  notice  of  the  Royal  Society,  I 
fhall  be  v^ery  glad  you  would  communicate  them.     In  order  to 
afcertain  the  going  of  the  pendulum  clock,  I  took  feveral  cor- 
refponding  altitudes  of  the  fun,  which  you  will  find  in  the  fol- 
lowing  table.     On  the  day  of  the  ecliple  the  Iky  was  very 
ferene,  nothing  could  be  finer,  and  it  continued  fo  during  the 
obfervation.     I  determined  to  ufe  an  achromatic  telefcope  of 
3!  feet  length,  that  fhews  obje<Sls  in  their  natural  pofition,  be- 
caufe  the  dikited  and  uncertain  te<"mination  of  the  true  fhadow 
of  the  earth  appears  more  perfectly  defined  by  fmall  than  by 
Vol.  LXXV.  T    '  large 


j^S  M  DE  Zach's  JJlronomicni  Ohfervatpons* 

large  telefcopes,  which  magnify  too  much,  and  give  too  great  a 
tranfit  between  the  penumbra  and  the  true  dark  fhadow.  On 
that  account  feme  celebrated  aftronomers  advife  to  ufe  for  the 
eclipfes  of  the  moon  no  greater  telefcopes  than  of  four  or  five 
feet  length.  It  was  remarked  at  Paris,  that  in  an  eclipfe  of 
the  moon,  obferved  through  a  tclefcope  of  DoLLOND,the  focus 
of  its  object  lens  being  30  inches,  and  likewife  through  a  tcle- 
fcope of  five  feet  length  ;  the  eclipfe  appeared  to  begin  4^  7^' 
fooner,  and  to  end  4^  Y'  l^ter,  through  the  fmall  than 
through  the  long  tclelcope ;  the  like  has  been  remarked  by 
feveral  others,  and  it  has  been  alfo  obferved  bv  mvfelf.  As  to 
my  obfervations  I  am  tolerably  fatisfied  with  them,  as  they  do  not 
differ  materially  from  thofe  of  Feather  le  Fevre,  though  it  is 
known  that  in  eclipfes  of  the  moon  no  greater  exa£l:nefs  than 
that  of  a  minute  can  be  obtained.  The  moon's  fpots  were 
carefully  obferved ;  for  it  is  known,  that  the  mean  of  the  ob- 
fervations of  the  moon's  fpots  is  fufficient  to  afcertaln  the 
longitude  of  a  place  to  4'^  or  ^"  nearly.  M.  de  la  Lande 
comparing  the  oblervations  of  the  moon*s  fpots  in  an  eclipfe, 
made  the  22d  of  November,  1760,  in  Vienna,  by  the  Impe- 
rial Aftronomer  Abbe  Hell,  with  thofe  made  at  the  fame 
time  in  Paris  by  M.  Messier,  finds  the  difference  of  meri- 
dians td  be  56^  ^o^"*  which  agrees  very  exactly  with  thatt  afccr- 
tained  by  other  means. 


Correfpondent 


M,  DE  ZACH'b  JJinoriomual  Ohfcrvatms^ 


J^39 


1-4 

o 


CO 

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T? 

rt 

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t> 

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m 

upper  limb 
horizontal 
aftern  fide 

b  at 
ude, 

rked 
day 

g     0, 

m's   upper  lim 
the  fame  altit 
weftern  fide     ■ 

he  fum 
ter  on 

anas  ma 
clock 
of  the 

rt 

fn          .       «J 

+-»  ^ 

^  'o 

he  fun'; 
at   the 
■wire, 

Dividing 
Sun's    ce 

mcridi 

by  the 
quution 

lock 
equate 

H 

(-0 

W 

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O 

a 


Z    H 


T  a 


19th 


140 


M  DE  Zach*s  Aj]ronomicc\l  Obfervations, 


iQih  March,   1783. 


tal  •\ 


The  futj's  upper  limb  at  the  horizontal 
wire  of  th^  firft  telcfcope  on  the  eaftern 
fide  -  -  .  J 

Sun's  upper  limb  at  the  fame  altitude  on 
the  weftern  fide  of  the  meridian 


Dividing  the  fum  by  2 

iiun's  center  x)n  the  meridian  as  marked  by\ 
the  pendulum  c'ock  -  -  J 

Equition  of  the  day 

Clock  (lower  than  equated  folar  time 


Sun's 
Altit. 


o  / 

3»   30 


Jfl  oblerva- 
tion. 


9  I  56 

H  31  47 


23  o^   43 

11  46  51I 

12  7  57 


o  21 


Sun's 
Alt. 


o 


lid  obfer- 
vation. 


h.    ,       ,,. 
9  13    9 


14    20    33; 


23  33  4^ 
II  46  51 

^2     7  57 


o  21 


Clock  flower  than  equated  folar  time  1 9th  March     21     6 
■  -■  i8th  March     19  32 

■.■■■■»M«|    ,         ■       H      I       III      II.       Ill  I  I  I 

Retarding  of  the  clock  upon  23  h.  58'  8"  -  I    34 

I  obferved  too  the  mid-day  at  the  great  gnomon  of  the  ob- 
servatory, and  found  at  the  fame  time  the  meridian  line  erro- 
neous by  I  ^'\  as  you  will  find  in  the  following  tables. 


When  the  center  of  the  fun's 
image  was  on  the  meridian  the 
time  pointed  by  the  clock  was 

Equations  of  thofe  days 


) 


the 
17th 
Mar. 


11  50  50 

12  8   33 


Retarding  onequjitcd  folar  time  17  a"^ 

Retarding  the  17th 

Retarding  of  the  clock  during  thofe  24.  hours 


the 
i8th 

Mar. 


h. 


/     // 


1 1  48  56 

12  8   15 


19  19 

17  43 


36 


the 
igth 
Mar. 


the 
i8th 


h. 


/      /' 


ii  47     3 
12     7  57 


20  54 
19  19 


I  35» 


I  fixed  therefore  the  retarding  of  the  clock  i'  ^^^\ 


True 


M.  DE  Zach's  j^Jlronom'ical Ohfervaiions. 


141 


True  mid-day  concluded  by  the  fun's  correfpon- 1 
dent  altitudes  as  the  clock  marked  J 

Equation  of  the  mid-day 

Retarding  of  the  clock  at  the  rate  of  i'  35"  1 
per  24  hours  -  -  -  J 

True   mid-day    the  pendulum    clock   fhould  | 

have  marked  -              -             -          J 

Mid-day   concluded  at  the    gnomon  of   the  1 

obfervatory         .  -          -          -               J 


Difference,    the  error    of   the  meridian   line 
or  gnomon  -  -  . 


the 
i8th 
Mar. 


II   48  42 
-    18 

+    13 


II   48  37 
II   48   56 


19 


the 
19th 
Mar. 


// 


II  46  51 
-  18 
+    II 


II  46  44 

II  47    3 


^9 


From  thence  I  concluded. 


h. 


Mid-day  at  true  folar  time      ii   5.9.60 
Mid-day  the    clock   flxould  1  ^ 

have  marked  on  the  1 8th  J         ^     ^' 


Retarding  upon  true  folar 
time 


} 


T-l    23 


Mid-dayatequatedfolar  time  12     8   15 
Mrd-day  the  clock  fhould  \  o 

have  marked  on  the  i8thj         ^     3/ 


Retarding     upon  equated! 
folar  time  *•  J 


19  38 


Obfervstionj 


■v 


■i4't 


M,  DE  Zach^s  Aftrommlcal  Ohferi^citions, 


Obfervations  of  the' moon's  ecllpfe  the  1 8th  March,   1783. 


•/ 

My  obl'eivations  with  ati  achromatic  teielcojie  of  33- 
feet  length. 

Timema-rked 
by  the. clock. 

True  or  ap- 
parent time. 

IMMERSIONS. 
The  bcgianing  of  the  eclipfe  very  doubtful, 
,  Shadow  touches  Grimaldi 
Grimaldi  all  in  the  fliadow 
Shatiow  touches  Mare  Humoruno 

7  4^  45 
7  42  54 

7  49  32 

8  0  21 

8     2  29 
8     6  18 
8   12   ig 

8  13  43 
8   lb     7 

8  21   31 

8  25  54 

8  32  21 

8  33  29 
8  35  36 
8  36  5^ 
8  38  57 

10  19  57 
10  23  33 
10  24    9 
10  29  34 

10  35  37 
10  43     6 

10  57  32 

11  15  44 
II  20  10 

h. 

7 

7 
8 

8 

8 

8 

8 

8 

8 

8 

8 

8 

8 

8 

8 

8 

10 

10 

10 

10 

10 

10 

II 

II 

II 

3 

53  39 

54  48 
I  27 

12  16 
14  24 
18  13 

24  15 

25  39 
2^     3 
33  27 
37  50 

44  18 

45  26 

47  33   ■ 

48  53 
50  55 

32     2 

35  38 

36  14 
41  39 
47  43 

55  12 

9  39 

27  51 
32  18 

39    0 

Copernicus  all  in  the  fliadow 
Tycho  touches  the  fliadow 

Mare  Serenitatis  touches  the  fliadow                » 

111   1  ti  f  nf*  ffTi<im\r                .                  ■■ 

Proclus  touches  the  fliadow 
Mare  Crifium  touches  the  fliadow 

oM   Tn   f  nf*  tlnniOU''                       .                         » 

Total  immerlion               -                -                *• 
EMERSIONS, 

Beginning  of  the  emerlioa 
Grimaldi  emerging 

Mare  Humorum  emerging 

Total  emerfion  of  INIare  Humorum 

Copernicus  all  out  of  the  fliadow 

Mare  Serenitatis  all  emerged 

Mare  Crifium  all  emerged 

End  of  the  eclipfe                      • 

Total  duration                   .                   .                    - 

Father 


M,  DE  Zach's  Ajlronomkal  Objervatlons. 


143 


Father   le  Fevre's  obfervations  with   a   refle(n:or  k,c^    niches 
focal  length,  magnltynig  300  times. 


I  ]M  M  E  R  s  I  o  N  s. 
Grimaldi  touches  the  fliadow 
Kepler  touches  the  ftiadow' 
all  in  the  fliadow 


Copernicus  touches  the  fliadow 
all  in  the  fliadow 


Mare  Serenitatis  touches  the  lliadow 
all  in  the  fliadow 


Mare  Crifiam  touches  the  fliadow 
. — .  all  in  the  fliadow 


Total  immerlion 

EMERSIONS. 
Beginning  of  theeraerfion 
Grimaldi  emerged 
Kepler  all  out  of  the  fliadow 
Copernicus  all  out 
Mare  Serenitatis  all  out 
Crifium  all  out 


End  of  the  eclipfe 
Total  duration 


Time  by  the 

Apparent 

clock. 

tiinfc. 

h- 

h. 

/     // 

7  41  43 

7  53  37 ■ 

7  52     2 

8     3  57 

7  53  24 

8     5   19 

8     0  22 

8  12  17 

8     2  26 

8   14  21 

8   16     7 

8  28     3 

8  26     2 

8  Z1  58 

8  r.  28 

8  45  25 

8  36  56 

8  48  53 

8  38  54 

8  50  52 

10   19  42 

10  31  47 

10  23. 24 

10  35  29 

10  35  43  • 

10  47  49 

10  43     4 

JO  55,  10 

10  57   19 

11     926 

II  ^s.  50 

II  27  57 

II   20  22 

11  32  30 

3  39  20 

The  oblervatlon  of  the  vernal  equinox  was  made  at  the 
gnomon.  The  height  of  this  gnomon,  taken- from  the  center 
of  the  hole  by  which  the  beams  of  the  fun  come  in,  is  1878 
lines  of  a  French  inch ;  the  diftance  from  the  bottom  of  the 
gnomon  to  the  equinoctial  point  is  1928  ;  the  diftance  from  the 
upper  limb  of  the, fun's  image  to  the  equinodlial  point  was 
found  16,7  ;  the  diftance  from  the  under  limb  23,4  ;  the  dia- 
meter of  the  hole  =  6  ;  therefore  the  diftance  from  the  bottom 
to  the  upper  limbi 928  -  16,7  + 3  -  1914,3,  to  the  under  limb 
1928  +  23,4-3=1948,4;  which  gives  the  time  the  equi* 
uox  happened  the  20th  of  March,  5  h.  56'  52''  P.M. 

4  Obfervations 


144"  M  r>E  Zach's  Ajlronomkal  Ohfervathm, 

Obfervatlons  of  Jupiter's  fatellites  at  Marfellles. 


178' 

Apparent 

Obferva- 

^  /  *-"- 

time. 

tion. 

h.     .       n 

April  3 

ImmerCon  of  the  Ift  fatellite  at 

- 

2    22    56 

good 

May  19 

Imm.  Ill:  fat.               -                    - 

-' 

2    48    12 

good 

June    7 

Imm.  IVth  fat.  was    not  total,  but  its 

light  diminiflied  fcnfibly  withoutj 

ever  difappearing  ;   the  fky  was  ferine, 

and  Jupiter  had  fix 

belts  very 

diainaiy. 

20 

Eraerfion  of  the  111  fatellite 

^ 

I    29    46 

good 

]'^''y   5 

Em.  lit  fat. 

- 

II  43  59 

good 

13 

Em.  Ild  fat.              .               ^                ^ 

9  17  28 

good 

20 

Em.  Illd  fat.              -  "^            >• 

9  27   13 

good 

20 

Em.  Ild  fat. 

i 

i»  51  59 

good 

21 

Em.  lit  fat. 

- 

10     111 

good 

27 

Imm.  Illd  fat. 

- 

10    40     '^T^ 

good 

Aug.  6 

Em.  lit  fat. 

4 

8  21  20 

good 

13 

Em.  Ill  lar» 

- 

10  18  49 

good 

14 

Em.  Ild  far. 

- 

8  55  3v 

good 

Sept.    I 

Em.  Illd  fat. 

* 

9  40  44 

doubtful 

14    Em.  Ill  fat-. 

- ! :  ,              i'  .        1                 "1                             '                                      r 

M 

8     6  48 

good 

IT  is  known,  that  the  indh-ect  method  to  calculate  the  orbits 
of  comets  in  a  conic  fedion,  by  means  of  three  obfervatlons 
given,  is  rendered  more  eafy  and  expeditious  if  there  is  a  pofli- 
bility  of  drawing  a  graphical  figure  that  reprefents  nearly  the 
orbit  under  confideration,  by  means  of  which  the  calculation 
is  directed,  and  the  required  elements  of  the  comet's  path  may 
be  rigoroufly  determined.  To  draw  the  orbit  of  a  comet  that 
moves  in  a  parabola  or  ellipfis,  the  problem  is  reduced  to  find 
the  potition  of  the  axis  and  the  perihelial  diftance  ;  this  por- 
tion of  the  axis  will  be  determined  as  foon  as  the  angle  Is 
known,  that  the  axis  forms  with  another  Hne,  whofe  pofition 
is  given  ;  this  line  may  be  an  ordinate  to  a  given  point  ot  the 
curve,  or  a  tangent,  or  a  radius  vector,  &c»     The  latter  is  to 

7  '^^ 


M.  DE  TjACus  AJlronomkal  ObfeiVc7tions.  145 

Le  employed  in  preference,  b^caufe  the  periheliiU  dlftance  being 
a  conftant  quantity,  the  angle  of  pofition  then  becomes  the  true 
anomaly  of  the  comet ;  but  as  the  data  of  this  problem  are 
■only  geocentric  longitudes  and  latitudes  of  the  comet,  de- 
duced from  the  immediate  oblervations  of  right  afceniion  and 
declination,  the  heliocentric  longitudes  and  latitudes  mufl 
firfl:  be  calculated  ;  but  as  thofe  data  are  not  fufficient,  what  is 
not  given  mud  be  arbitrarily  fuppofed,  viz.  the  (hortened  ^\(' 
t2inQts(diJiantias  cur  tat  as). This  fuppofitionis  changed  and  altered 
until  the  calculation  will  agree  with  the  three  obfervations, 
then  the  difference  between  two  longitudes  is  the  angle  com- 
prehended between  the  two  (hortened  diftances  in  the  planeof  the 
ecliptic  ;  the  whole  reduced  to  the  plane  of  the  comet's  orbit  by 
means  of  the  heliocentric  latitude,  gives  the  difference  between 
'the  anomalies  comprehended  by  two  radius  vectors,  the  problem 
then  is  reduced  :  two  radius  vedors  being  given,  with  the  angle 
comprehended,  to  find  the  two  true  anomalies,  the  perihelial 
distance,  and  the  time  the  comet  puts  in  running  its  anomalies. 
Let  therefore  t  s  =^yf  reprcfent  the  ecliptic  at  an  infinite  dlf- 
tance ;  QPR  the  apparent  elliptical  or  parabolical  path  of  a  co- 
rnet; S  the  fun's  center;  P  the  comet's  perihelion;  T  the  place  of 
the  earth  when  the  comet  was  firll  obferved  in  C  ;  I  the  earth's 
place  when  the  comet  was  obferved  in  K ;  ST  =r  ^,  S\  —  ^,  the 
diflances  from  the  earth  to  the  fun  at  the  firfl  and  fecond  obfer- 
vation  known  by  aflronomical  tables ;  let  Cm  and  K^  be  two 
perpendiculars  to  the  plane  of  the  ecliptic,  it  will  be  Sm^Uy 
S«  s=  u  the  two  fhortened  di{lances> 

The  obferved  geocentric  long-itude  of  the  comet  in  T:^5=:arc  T  "v^G  j 
the  obferved  geocentric  longitude  of  the  comet  in  I=ra~arc  V  ViJ'H; 
the  geocentric  longitude  of  the  fun  by  tables  in  T~^r=arc  TVy=^A; 
'the  geocentric  longitude  of  the  fun  by  tables  in  Ir:^  — arc  T  ViJ'riBii 

Vol.  LXXV.  U  Now 


14^  ^'^-  EE  Zach*s  Ajlronrymlcal  Ohfervattom, 

Now  for  the  hrft  obfervatlon  the  angle  of  elongation  \%h  --  a\ 
for  the  aDG:le  ATG  =  arc  AG  =  t  'f^-^K  —  t  ^/5 G  ^  lono-.  o  — lon^^v 
eornet  —  b  —  a\ 

the  anqle  of  the  animal  parallax  S;;2Ti=""''  ~"'    =<:' : 

the  angle  cf  commutation  wST=  jg^.  -  ^+  (3  — <3)  =y; 

from    whence    the    heliocentric     longitude    of    the    comet  =^ 

The  iiime  at  the  fecond  obfervatlon  in  I. 
Angle  of  elongation  =.  /3  —  oi ; 

Air                I            n                ^'"'-  v*^— *)  '^ 
Anjrle  or  annual  pa^-allax  g  — ; 

Angle  of  commutation  ^  =  i3o^~"  e  +(/5  -  a)  ; 
heliocentric  longitude  of  the  comet  in  I  =  /3  —  1 8o°  +  (p  =  ^ 7 
putting  now  the  heliocentrie  latitude  feen  from  S  =  /^  ;- 
the  geocentric  latitude  feen  from  T  — /;.; 

17     1-  •     1      •        T  '11   1       fin. /".  tane.  /  , 

the  heiiQcentric  latitucie  will  be  •-, -  •'   ,  ■    \  :=:  tans:.  ^  ; 

7        r  •   1     Tr      •  "11  1       fin    ®  .  tan<r.  ^  i     i* 

the  lame  with  li«  it  wiii  b€  — . '  ^  ■  ^  ■"  -  =-•  tanp".  y.  heliocentna 

iin.  (i3  — Ji)  ° 

latitude  in  K. 

Having  thus  determined  th-e  heliocentric  latitudes  of  two 
obfervations,  the  radius  ve6lors  will  eahly  be  found  in  the  fup- 
polition  made  for  the  fhortened  drllances,  for  they  are  in  the 
lame  ratio  to  the  radius  veftors  as  the  coiine  of  the  heliocen- 
tric latitudes  are  to  the  radius  =  i  ;  therefore  the  radius  ve6toF 

m  of  the  firfl:. obfervatlon  willbe=:~.-  and  the  radius  ve6lor  of 

col,.  ,4 

the  fecond  obfervatlon  u  —  ——-  . 

'  col.  y. 

Taking:  now  the  difference  between  the  found  heliocentric 
longitudes,  we  get  the  heliocentric  motion  of  the  comet  upon 
the  ecliptic  between  two  fliortened  diflances,  which  is  to  be 
redu-ced  upon  the  comet's  orbit,  this  heliocentric  motion  Is 
tjiercfore  7  -.§■  =^  /^.     Now  to  reduce  this  motion  we  have,  firfl-, . 

finus 


li'L  l>E  Zacu's  Aft ronomicjl  Qi)ft;rv£tt ions,  14.7 

lliius  totus  =  I  is  to  coliiie  .-7;  ::  as  cotangent  k  is  to  the  tan- 
gent of  an  angle  which  1  put  =  ;7,  and  90°  -  i -p /Z  will 
give  an  angle  which  I  put  =  q,  Luflly,  the  analogy 
cof.  «  :  cof.  q  ::  fin.  k  ;  w^ili  giv^c  the  cofme  of  an  angle  if/, 
wliich  is  the  requircu  motion  upon  the  orbit,  or  the  angle 
compreheaded  between  the  two  radius  vectors  w  and  ^,  l.t't 
therefore  ECPMND  be  the  apparent  parabolic  path  of  a  comet ; 
S  the  lull's  center;  ]\'I  and  N  two  places  of  the  comet,  the  angle 
MSN  equal  to  its  motion  in  longitude,  or  thie  comprehended 
■angle  if/ ;  P  the  perihelion  ;  it  is  required  to  find  the  two  ano* 
malies  PAI,  PN,  that  is,  PSM  and  PSN,  the  perihelial  dif- 
tance  SP,  and  the  time  the  comet  employed  to  come  from  its 
perihelion  P  to  M  and  N. 
Refolution. 


:SM  =  7n 

•SNrr^ 

MSN  -  ^ 
NSB  :=  .V 

MSB=(iI;r±^^) 

Parameter  =p 


In  the  right-angled  triangleSMRand  SNVwe  have 
MR  =  OS";;/fin.  (4.=t:.v)  N  V  =:  QS=:^  fm.  .r; 
therefore  OP—  Ip  —  m  (fin.  4^  —  -^0  ^^^^  PQ^ 
\p^lJi.{\Vi.x\  but  by  the  natureofthe  parabola 
w^ehaveSMz:.AP^POaiidSN:=AP  +  PQ;thatis 
V2':=,\p  —  m  (tin.  ipzt.v)  1^,=  ipz:izf4,  fin.  .v   , 

m  +  m  (fin.  4^=tzx^  ~ip         f^  —  H'  ^^^^'  ^~i  P 
/;/  (  I  +  fim  ij;±.v)  rr  {p  ^.t  (l  rp  fm.   x')  =lp 

Slid    I  -f  fin.  (iLdr.v")— -^  I    =i=  fill.  X  :=   ~\hY 

putting  Into  a  fum  i  +  fin.  (4/  — a*)  +  i  t±rfin.  .v  t=:  —  +3^  ;  reduc- 
tion made  2^fin.  x ^(\i\.  (iP'^t^v)  =  ^-^-7-^)  p  ;  but  by  trigono- 
metrical formulae  we  have  (in.  (ij;— .v)=:lui.  4^  cof.  ATrtrfin.  x 
^of.  ip.     Subftituting  this  exprefTion   in   its    place  we   obtain, 

2  ^ fin.  x-\-  fin.ip  cof..Vrt:fm .  x  cof.vl'  =  ( ^~ — ^  j  />.  By  the  fame 
formulas  we  have  cof.-  x—i^  fm.^  a;  and  cof.  x  —  s/\  -lin. 


U    2 


X\, 

Sub-' 


43 


M,  DE  Zach*s  /IJirGnonncal  O!)fervatlons. 


o 


w 


I 

« 

if 


3 
O 

(/) 

a 

o 
o 


WD 


S3 


+ 


O 


-h 

o 


41 


c 


cs 


i 
cs 

1+ 


5 
I 

o 
u 


CO 

?^ 

o 
u 


1.1 


r.     S 


+ 


o 

o 

4-1 


o 

C! 

g 
O 

*— I 

o 

a 
s 

o 


s 

o 


H       D 


o 


+ 
+ 


i 

<N 

+1 
>. 

C 

+ 
i 
+ 


5 


<D 


<L> 

B 


:=:  bD 


<u 


S 


-a 

Q 


a 


^     ^   ^ 


J3 


o 


►^-^ 

r« 

• 

a 

>s. 

U-. 

• 

o 

a 

^ 

^ 

■h 

C     d 
O    « 

5 
+ 


(S 


iJ<f.  DE  Zach^s  JJlronomical  Obfervatiojis, 


14  f 


If 


c 


«— ■ 

O 
o 

c 


If 


a. 

I 
J* 


a. 
II 


c) 

\ 
H 


If 
H 


a. 

II 

3. 

5 
-«* 

f 

c 


H 


i:;- 


r\ 


II 


o 

i. 


c 

(D 

ciri 


■"        -5    ^ 


+ 


ST 


i>    ' — - 

O      S- 


<o 

^^ 

> 

V-: 

t^ 

0 

u 

«\ 

CM 

CO 

5 

-CJ 

14- 

cz 

IT 

s 

-> 

■^ 

(-• 

0 

»— « 

CJ 

-a 
U4 


II 


o 


+ 


If 


-> 


o     ^ 


•fl 


+ 


-^- 


r     • 

0 

<— 1 

u 

0 

s. 

0 

m 

Uh 

»v 

0 

0 
1 

r3 

1 

c: 

"P- 

<u 

t* 

ei 

G 

c 


-» 


CO 

'bb 


u 


^ 


-d- 


o 


-^ 


-tJ- 


^    .2 


■^        ^ 
*-  t 


bI3     <45 


3 


3   II 


If 

a. 

d 


II 


-^ 


I 

■t 

+ 


II 
li 

»-« 

o. 


XTO  M  DE  Zacii's  AJlrcnomlcal  Ohferja'/iQtu-, 

The  angle  .v  defines  tlierefore  the  pofitlon  of  the  axis  and 
the  two  anomalies  required,  the  perihelial  diftance  being 
_^  -=  2^:±:  2^7,  lin.  .v,  it  will  be  known  alto  by  the  angle  .v. 

In  order  to  find  the  thne  the  comet  emplovs  in  runnino'  its 
anoinalies,  let  the  perihelial  dlftatice  jnd:  now  invefl:igated^/>  be 
equal  to  the  radius  of  the  earth's  orbit,  the  parabolic  area 
i\vept  by  the  radius  vector  will  be  by  the  nature  of  the  para- 
bola  !  PQ  X  OM  4- 1  SO  X  QAI  :=.  :^- ^  ^  ^^^  +  ^so  x  OM  ^     ^^^^ 


.  44 

44,       r.  22 


tlie    periphery    of    the    earth's    orbit    is     j  \  2Z  \:  2p '.  ~p\ 


therefore  the  whole  area  -p.lp—~—  p^.     It  is  known  that  the 

velocity  of  a  heavenly  body  moved  in  a  circular  path,  is  to 
the  velocity  in  a  parabolic  path  in  the  ratio  v/2  :  i.  If  the  pa- 
rabolic area  -of  the  comet  is  divided  by  s/z  it  comes  out 
^ A equal  to  an  area  that  the  earth -deicribes  111 

the  very  fame  time;  put  therefore  A  equal  to  the  time  of  a 
fidereal  year,  we  (hall  recover  the  analogy ;  the  whol-e  area  of 
the  earth's  orbit  is  to  the  time  in  which  it  is  defcribed  as  the 
parabohc  area  is  to  the  time  con  fumed  in  fweeping  it ;  therefore 

-If  ,  A  :,   j4j^-^  3SOIMO  .   7A(4l-O  +  3S0)MO.       ^^^     Qj^j^ 
7  6v^2  ^  'jip^'^z 

SM  .  fin.  anom.  PSM  and  OS  =:  SM  .  cof.  anom.  PSM  ;  let 
the  anomaly  he  —  S,  we  have  OM=:/7/  fni.  ^,  and  OS  z=:}?i  cof  5; 
therefore     PO  ~  p  —  m     cof.    ^.       SublVitutlng    we    obtain 

i — ^-^ — — = which  IS  - — -^ =i — ■ , 

'thereby  the  time  is  found  in  parts  of  a  fidereal  year. 

I  am,  &c, 

SiPv, 


^M,  DE  Zacii*s  Afirtnomlcal  Ohfervji'ioni,  T'5'i. 

SIR,  Lyons,  >:f,y  4,    i)3j. 

Lately  1  recelveJ  from  the  Obfervatory  at  Marlllllcs.the 
oblervatlon  of  the  tranfit  of  Mercury,  which  happened  the  izrii 
Nov.  1:82.  The  fkv  not  beuijr  verv  favourable,  only  the  two  in- 
tcrnalcontafls  were  obferved  ;  the  firfl:  internal  conta£l  was  oh- 
iervcd  by  M.  St.  Jacques  df,  Sylvabelle,  at  3  h.  18^  30'^^ 
apparent  time  ;  the  lafl  internal  contact  by  M.  St.  Jacques,  at 
4h.  33^  16'";  by  M.  Bernard,  his  Adjunclns,  at  4  h.  29'  i^'\ 
The  neareH-  diftances  of  Mercury's  limb  to  that  of  the  fun  in. 
the  northern  part  of  its  diik  were  at 


h. 


3  dZ  14' 

51  ^ 

3  42  SI 

.  34    > 

4  22  I J 

^9  . 

parts  of  the  micrometer. 


The  apparent  diameter  of  the  fun  was  2174  parts  of  this  mi- 
crometer :  I  fuppofe  the  before-mentioned  2174  parts— 32-^ 
26^^,9.  I  conclude  farther,  by  the  obfervations,  the  middle  of 
the  tranfit  at  3  h.  54^  ''/\'^S->  ^^^J^r^^s  I  fix,  by  interpolation, 
the  diftances  of  the  limbs  at  3h.  54^  7^^,2:5  =  35^'', 6  ;  I  have 
therefore  femi-diameter  of  the  fun  =:  16'  13^,4-35^^,6  =: 
15^  37'''?8  +  femi-dlameter  of  Mercury  =  6^^  :=  15^  43'^8  ^rtO'the 
leaft  diflance  of  centers  of  the  fun  and  Mercury.  By  M.  de. 
la  Lande's  tables  it  is  15''  42'',.  only  a  ditFerence  of  \'\%. 

M.  Wallgt  at  Paris  has  obferved  this  tranfit  at  the  Royah 
Obfervatory,. 

Firfl:  external  con ta:f):     2   56   28 

Firfl  internal  conta(ft  3     '^     3. 

Second         -         -  4   ^7    18 

Second  external      -  4,  22   53. 
5.^  lonl/- 


152  M.  deZach's  AJlronomkal  Objerv^Uions, 


I  only  add  an  important  remark  upon  the  diameter  of  Mer- 
cury, which  the  aftronomers  fuppofed  in  this  tranfit=:  1 1^\ 

Let  ABC  reprefent  the  fun's  di(k  ;  in  P  an  external  in  Q^an 
internal  conta(fl;  ANC  the  apparent  path  of  Mercury  over  the 
fun. 

Thefemi-diameterof  the  funir  972''^,  this  of  Mercury  in  our 
fuppofitionrr6^%  MN  =  942'^  the  leaft  diftances  of  the  centers. 
In  the  right-angled  triangle  MNP  it  is  MP  :=:  972''  -f  6''  =  978'', 
MQ  =  972''^-6''r=966'';  therefore  NP  will  be  foundr:26o'' 
and NQr:  2 1  o^'' :  now  NP— NQ=PQ^r:  50",  which  converted 
into  time  gives  8'  14^^  for  the  time  the  diameter  of  Mercury  em- 
ployed to  run  over  the  limb  of  the  fun ;  but  by  the  obfervations 
of  M.  Wallot  I  find  this  time  conflantly  in  both  contacts 
5'  35^^  >  therefore  8'  14''  :  12''  ::  5^  35'^  :  8^^137,  which 
{hould  be  the  diameter  of  Mercury ;  and  indeed  M.  Wallot, 
by  an  immediate  meafure,  taken  with  an  excellent  wire-micro- 
meter, finds  this  apparent  diameter  not  greater  than  9'^,  which 
fufficiently  fhews  that  this  diameter  fuppofed  7''  ia  the  meaa 
4iltance  is  alfo  too  great, 

I  am,  &c. 


P/i,l,:<.T>ri  ru.lW.l.XXI :  Tab.V  I .// 


/ 


[     ^53    ] 


IX.  Obfcrvatlons  of  a  new  Variable  Star.  -By  John  Goodrick6, 
Efq.\  communicated  by  aS/V  H.  C.-Eiigldkld,  Barf.  F.  R,  S^ 
and  A.  S. 


Read  Jannary  27,   1785 


TO  SIR  K.  C.  ENGLEFIELD,    BART. 


**^.l  ^HE  account  that  has  been   lately  given  of  the  regular 
variation  of  Alfrol's  liRht,  and  the  notice  aflronomers 


'&^"  "   "  t) 


DEAR    SIR,  York,  Jan.  10,   178^. 

T 

have  been  pleafed  to  take  of  it,  are  well  known.  It  is  natural 
tiierefore  to  fappofe,  that  the  relation  of  other  fimilar  pheno- 
mena may  alfo  meet  with  the  fame  flivourable  reception.  Of 
tnis  kind  is  the  following,  -^hich  I  begthe  faveur  of  }^ou  to 
^prefent  to  the  Royal  Society. 

On  the  I oth  of  September,  1784.,  whilfl:  my  attention  was 
diredled  towards  that  partof  the  lieavens  where  /3  Lyne  was 
lltuated,  I  was  furprifed  to  find  this  ftar  much  lefs  bright  than 
iifual,  whereupon  I  fufpedted  that  it  might  be  a  variable  flar  : 
my  fufpicions  were  afterwards  confirmed  by  a  feries  of  obfer- 
vations,  which  have  been  regularly  continued  fuice  that  time, 
and  which  will  pvefently  follow  in  their  proper  place.  At  firll: 
Lthought  the  light  of  this  flat  fubje(5l  to  a  periodical  variation 
•of  nearly yFv  days  and  nine  hmirs^  though  the  degree  of 'its  di- 
minution did  not  then  appear  to  be  conftant ;  but  now,  lipon  a 
-more  clofe  examination  of  the  obfervations  themfcives,  I  am 

V^L..  LXXV.  X  inclined 


1^4  ^^'  Goodricke's  Obfervations 

inclined  to  think,  that  the  extent  of  its  variation  is  twelve  days, 
and  nineteen  hours,  during  which  time  it  undergoes  the  fol- 
lowing changes. 

1.  It  is  of  the  third  magnitude  for  about  two  days. 

2.  It  diminilhes  in  about  one  day  and  a  quarter. 

3.  It  is  between  the  fifth  and  fourth  magnitude  for  lefs  than 
a  day. 

4.  It  increafes  in  about  two  days. 

5.  It  is  of  the  third  magnitude  for  about  three  days. 

6.  It  diminishes  in  about  one  day. 

7.  It  is  fomcthing  larger  than  a  ftar  of  the  fourth  magnitude- 
for  little  lefs  than  a  day. 

8.  It  increafes  in  about  one  day  and  three  quarters  to  the  firft 
point,  and  fo  completes  a  whole  period. 

Thefe  eight  points  of  the  variation  are  perhaps  inaccurately 
afcertained  ;  and  indeed  it  cannot  be  expelled  to  be  otherwife  in 
eflimations  of  this  nature,  where  it  is  very  poffible  to  err  even 
feveral  hours. 

The  relative  brlghtnefs  of  jG  Lyra;,  at  its  obfcuratioii  in  the 
third  and  feventh  points,  is  nearly  as  follows.  When  in  that  of 
the  third  point,  it  is  lefs  than  ^and  x,  and  nearly  equal  to 
^  Lyras ;  and  when  in  that  of  the  feventh  point,  it  is  rather 
lefs  than  J  and  5  Herculis,  and  much  brighter  than  ^,  jc,  and 
2  Lyras.  At  its  greatefl:  brightnefs  in  the  firfl:  and  fifth  points^ 
it  is  fometimes  brighter  than  y  Lyrae,  but  lefs  than  /3  Cygni,. 
and  fometimes  only  nearly  equal  to  it  5  but  in  thofe  points  it 
fcems  to  alter  in  its  brightnefs  feveral  times  in  the  fame  night,, 
and  that  generally  in  a  pretty  confiderable  degree.  However,, 
this  may  perhaps  be  only  owing  to  fome  fallacy  of  obfervation  ; 
for  I  have  often  perceived,  that  the  relative  brightnefs  of  ftars 
is  affeded  not  only  by  the  different  flates  of  the  air,  but  alfo  by 

their 


t>f  a  new  Vatiable  Star,.^  155 

their   change   of    poiitloii   occafioned   by  the   earth's  diurnal 
motion,  and  that  particularly  in  ftars  of  a  great  altitude. 

The  magnitudes  of  the  ftars,  to  which  /3  Lyrce  was  com- 
pared during  the  progrefs  of  its  variation,  are  as  follows. 
/3  Cygni  and  y  Lyrae  of  the  third  magnitude  ;  |  and  5  Kerculis 
of  between  the  fourth  and  third  magnitude ;  0  Herculis  is 
fomething  lefs  than  a  ftaf  of  the  fourth  magnitude;  ^,  k,  audi 
^  Lyr;£  are  ftars  of  between  the  fourth  and  fifth  magnitude,  if  - 
hot  nearer  the  fifth.  The  relative  brightnefs  of  thefe  flats 
follows  the  order  in  which  they  are  fet  down. 


Ohfervat'ions  of  ihe  brlghtnefi  and  magnitude  of  13  Lyrae. 

1784,  Sept.  10.  At  1 1  h.  =*=,  much  lefs  than  y  Lyras; 
nearly  equal  to,  if  not  rather  brighter  than  f,  x,  and  S  Lyras, 
and  not  fo  bright  as  |,  ^,  and  c?  Herculis ;  between  the  fourth 
and  fifth  magnitude, 

Sept.  II.  At  8|  h.  nearly  the  fame  as  it  was  lafl  night,  if 
not  brighter;  indifferent  obfervation. 

Sept.  ,12.  At  8|  h.  and  ph.  between  the  third  and  fourth 
magnitude ;  lefs  than  y  Lyras,  brighter  than  5,  |,  and  0  Her- 
culis, and  much  brighter  than  f,  jc,  and  S  Lyrae.  Mr.  E. 
Pi  GOT  T  agrees  with  me  nearly. 

Sept.  13,  15,  18,  19,  and  20.  It  was  at  or  near  its  greateft 
brightnefs. 

Sept.  23.  At  yi  h.  it  was  nearly  eqjual  to  ^,  x,  and  0  Lyrae, 
and  much  lefs  than  ^,  9,  and  0  HercuHs. 

At  io|  h.  the  air  being  extremely  clear,  Icompared  it  more 
attentively  to  the  neighbouring  ftars,  and  found  it  as  follows  : 
rather  a  little  brighter  than  $,  a  little  lefs  than  f,  and  rather 

X  2  lefs 


3.-56"'  A//'. -Goodricke's  Obfcr'uattons 

kfs  thaii  >i  LyrEc.     Mv.  B.  Pigot-t  thought  it  had  rather  in- 
cceafed  from  8|  to  1 1  h.  '     ; 

•Sept.  24,  At  i3-ll>.  certainly- brighter  than  it  was  lafc  nighty 
but  intervening  clouds  precluded  all  further  obfervation. 

Sept.  28.  At  i.ah.  not  quite  fo- bright  a-s  7  Lyrye,  but  rather, 
brighter  than  Q  a?id  |  Herculis.  Mr.  E.  Pigott  thought  it* 
nearly  equal  to '}/,l.jr{f.  .  .  . 

Sept.  29.  At-ji  h.  not  lobright  a-s-^  Lyrs*.- 
At  8f  h-.  to  TO'I  h.  nearly  equal  to  |  and  Q  IlercuHs;  but  ifi 
any  thing  it  feenned  rather  lefs- than  f,  and  rather. hi-igliier.thaii. 
^:   about  the  fourth  n^aG[nitude. 

At  1 1  5  h.  to  -izi  b.  the  fame,  if  notlefs  ;  I  could  not  compare 
it  welt  to  J  and'^,  becaufe  they  were  low  ;  moon-light,  bu-t  the 
air  was  clear. 

Sept.  30.  At7h.  rather  lefs  than  ^,  if  hot  equal  Jro  it;  a 
iittle-  lefs  than  1^  and;  brighter  than  0  Herculis  r  about  the- 
fourth  magnitude.   '   *' '^  " 

At  II  h.  and  125  h.  it  feenied  to  be  on-  its  ihcreafc,  beinir 
for  the-moft'part  larger  th'an  J  and  '5  Herculis-. 

061.  1  and  2.  About  its  greatefl:  brightnefs,  but  lefs  than* 
^''fcyVi'.'"  Mi".  E.'  PlGOTT  thoug-ht  it  brighter  on  the  2d 
than  on  the  if!:,  being  on  the  2d' nearly  equal^  to  ^Eyras.  '"  '"'" 
Oct.  4.  At  lorh.  I  thought  it  rather  lefs',.  but'-the  weather- 
was  hazy.  i'ot)i^i 
Oct.  5.  At  6|  h.  not  fo  bright -as  J' and '^  Herculis  ;  a  little  - 
brighter  than  ^,  and  brighter  than  ^  and  k  Lyrie ;  air  clear. 

At  9!  h.  nearly- equal  '.0  ^,  and  a  little  brighti^r  than  §and  ?& 
Lyra;.  • 

At  I2i  h.  a  little  lefs  than  ^,  nearly  equal  ta  >«,  and  rather  a 
little  brighter  than  0  I  .yra' ;  between  the  fourth  tind  fifth  mag- 
nitude ;  air  very  clear» 

5:  ^  oa 


of  a  neis)  Variable  Star.  '.i-:;rj 

Odl.  6.  At  hi  h.  and  7I  h.  Ids  than  f  and  y.,  and  a  little  lefs 
diaii  ^  Lyriie;-  between  tlje  filth  and  fourth  magnitude. 

Oct.  7.  At  6|  b.  between  the  tourtli'  and  tlurd  magnitude.; 
a  little  brighter  than  ^,  and  nenrly  equal.to-J  Herculis ;.  much 
brighter  tlian  f,  ;c,,  and  ^  Lyra: ;  1  obierved'k  tiii  \zk  ii-  when 
it  was  certainly  increaled. 

At  '/iho.  Mr=,E.  PiGOTT  thought  it.  brighter  than  J  and  5 
Herculis. 

Odi.  8.  At  S  b.  nearly  equal' to- 7  Lyr^e  ;  on  account  of' tlie 
intervenin-g  clouds,,  I  could  not-  perceive-  which,  was  largeft ; 
third  magnitude.  .-. 

.061..  9.-    At.  7  h,  rather  lofsthan  y  Lyn^; 

■  Ocl.  10..     At   ^h.  .i-iih.  aiid  12  h.   nearly  equal  to  7,  if 
-not  rather  lefs. , 

Oct.  II..  AtSh.  I  oh.  and  i'2  hv  rather  lefs  than  y;.  sat 
I  2  h.  if  any  difference,  lefs  than  it  was  lafl:  night.  .  -i 

0.(£l.  15..  At  8. h.=i^  nearly  equal,  to,  though  rather  lefs 
than,  9/ Lyne. 

,     06t  1 6 .     hx.  6 1 .  h . .  and  9 1  .h . ,  little  lefs  .than  .7,  if-  not  ecjaal 
•to  it .  . 

At  1 1  h.  rather  larger  than  <j^,  but^  th-e  weather-  was>  fogjxv-, 
Mr.  E.  Pi  GO  T  T  agrees  Avkh  me  in-  both  obfervation  s. 
-     0(51:.  17,.     At  6i  hJand  7  h*  fomewhat  lefs  than  y  Lyrir-.  • 
t'    Qdi,  18.     At  6|  h.  between  the  fourth  anxl  fifth  magnitude; 
brighter  than  k  and  ^,  and   rather  brighter  than  ^Lyra^;  good 
obfervation. - 

At  9|.h.  I  i  thought  it  was  decreafed,  being,  equal  to  f  anoi 
rather  brighter  than  ?<:  Lyrae.  Mr.  E.  Pigott  alfo  thought  it 
was  decreaiing. 

Od.  19.  At  6|  h.  it  was  rather  lefs  than  ^  and  ?tj  and 
brighter  than  I  Lyrasi 

■  '#/  At? 


15^  ^'^f*  Cjoodr  ick e's  Obfervaiions 

At  8|  h.  nearly  the  fame,  if  not  Increafed, 

Ode.  20.  At  6 1  h.  rather  brighter  than  J  and  5  Herculls,, 
and  between  the  fourth  and  third  magnitude.  ' 

At  8|  h.  and  1 1  h.  I  thought  it  \vas  increafed,  but  it  was 
lefs  than  y  Lyrae  ;  between  the  third  and  fourth  magnitude. 

0£t.  22.     At  6  h.  8  h.  and  9  h,  nearly  equal  to  y  Lyrae. 

Od.  23.  At  6  h.  8  h.  and  1 1  h.  rather  lefs  than  y,  though 
nearly  equal  to  it. 

Odi.  24.  At  62  h.  and  1 1  h.  lefs  than  y  Lyrae,  and  brighter 
than  J  and  Q  Herculis;  at  8  h.  Mr.  E.  Pigott  thought  it 
rather  lefs  than  y  Lyrac. 

05:.  25.     At  6  h.  8  h.  and  1 1  h.  nearly,  though  perhaps  not 
quite  equal  to  ^  Herculis ;  lefs  than  J  Herculis,  and  brighter ' 
than   ^  and  I  Lyrac;  about  the  fourth  magnitude.     At  6|  h» 
Mr.   E.   Pigott   thought   it   rather    brighter  than    Q   and   0 
Herculis. 

061.  26.  At  6  h.  and  1 1  h.  brighter  than  Q  and  0  Herculis, 
but  lefs  than  y  Lyrae. 

Odi,  27.  At  6  h.  and  8|  h.  brighter  than  it  was  kft  night, 
but  ftill  lefs  than  y  Lyrae ;  much  brighter  than  J  and  6  Her* 
culis ;  the  moon  was  at  its  full. 

061.  28.     At  8  h.  it  rather  lefs  than  y  Lyrae. 

0£l.  29.  At  91  h.  nearly  equal  to,  though  rather  brighter 
than  y  Lyrae ;  I  faw  them  but  for  a  (hort  time  on  account  of 
clouds  coming  on. 

0(5t.  31.  At  8  h.  between  the  fifth  and  fourth  magnitude; 
lefs  than  f  and  h,  and  brighter  than  ^  Lyrae.  Mr.  E.  Pigott 
thought  it  equal  to  ^  Lyrae  at  8|  h. 

Nov.  I.  At  6ih.  between  the  fourth  and  fifth  magnitude; 
tather  brighter  than  f,  and  brighter  than  )c  and  ^  Lyrse. 

Nov.  3,     At  5i  h.  little  lefs  than  y  Lyr«, 

Nov. 


of  n  new  Variable  Star.  1551 

Nov.  6.  At  8  h.  rather  lefs  than  y  Lyrae,  and  brighter 
than  5  Herculis.  Mr.  E.  Pigott  thought  it  nearly  equal  to  y 
Lyrae. 

Nov.  7.  At  7  h.  and  io|  h.  much  lefs  than  y  Lyrae; 
nearly  equal  to,  if  not  rather  brighter  than,  Q  Ilerculis,  and 
rather  lets  than  J  Herculis;  between  the  fourth  and  third  mag- 
nitude. 

Nov.  10.  At  io|  h.  nearly  equal  to  y  Lyi'ae.  Mr.  E. 
Pigott  thought  it  not  quite  fo  bright  as  7  at  1 1  h. 

Nov»  II.  At  5I  h»  and  7  h.  a  little  brighter  than  y  Lyric ; 
afterwards  I  rather  thought  them  equal,  though  Q>  appeared 
for  the  moft  part  fomething  brighter.  At  1 1  h.  and  12  h.  they 
appeared  nearly  equal.  At  7  h.  Mr.  E.  Pigott  thought  it  was 
lefs  than  y,  if  there  was  any  difference. 

Nov.  12.  At  6|  h.  81  h.  and  10  h»  much  lefs  than  7/ Lync, 
but  brighter  than  £  and  Q  Herculis ;  between  the  fourth  and 
third  magnitude. 

Nov.  13.  At  6|  h.  and  loh.  equal  to,  if  not  rather  lefs 
than  f,  lefs  than  ;c>  and  brighter  than  ^  Lyrae ;  between  the 
fifth  and  fourth  magnitude.  At  5I  h.  Mr.  E..  Pigott  thought 
it  rather  brighter  than  ^  Lyrae. 

Nov.  16.  At  7I  h.  little  lefs  than  y.  At  loh.  certainly  a 
little  brighter  than  it. 

Nov.  17.  At  6  h.  rafiher  brighter  than  y.  At  8^  Ii.  9I  h. 
and  loi  h.  brighter  than  y^  and  lefs  than  j3  Cygni. 

Nov.  18.     At  9  h.  10  h.  and  i^h.  juft  the  fame. 

Nov.  19.  At  6 1  h.  and  8  h,  lefs  than  y  Lyrx,  and  brighter 
than  6  and  |  Herculis  ;  between,  the  third  and  fourth  magnitude-. 
At  10  h.  fomething  brighter  than  5  Herculis. 

Nov.  20.  At  7  h.  8h.  and  loi  h.  rather  lefs  than  |,  ancf 
rather  brighter  than  Q  Herculis ;  between  the  fourth  and  third 

^  magnitude^ 


t€o  Mr,  Gooduicke's  Obfervatwns 

inap^aitude.     At  i8|  h.  I  thought  it-was  mcreafed  ;  obferved  in 

t-wi  light. 

Nov.  21.     At  7"h.  fomething  brighter  thriii  ^  and  J  Herculis, 

Nov.  25.  At  7  h.  lefs  than  y  Lyra?,  and  brighter  than  5 
Ilerciills  ;  between  the  fourth  and  third  magnitude.  At  9I  h. 
I  thought  it  v/as  decreafed,  being  now  of  the  fourth  mag- 
nitude. 

Nov.  26.  At  9:h.  =h  much  lefs  than  7/,  and  of  between  the 
fourth  and  fifth  mngnitude ;  but  the  weather  was  too  hazj, 
and  the  moon-light  too  ftrong,  to  obfcrve  well. 

Nov.  29.  At  72  h.  and  8  h.  rather  brighter  than  y  Lyrae. 
Mr.  Edw.  Pigott  thought  it  nearly  equal  to  y  at  8  h. 

Nov.  30.  At  8|  h.  and  io|  h.  brighter  than  y  Lyra?,  and 
lefs  than  /3  Cygni ;  air  clear. 

Dex:.  4.  At  5I  h.  6|  h.  and  io|-  h.  lefs  than  7  Lyra^,  and 
brighter  than  6  Herculis ;  between  the  third  and  fourth  mag- 
nitude.    Mr.  E.  PiGOTT  thought  it  nearly  equal  to  y  at  6|  h. 

Dec.   9.     At   8  h.  much    lefs  than    y   Lyrae,   and   brighter 
than^Lyrie;  about  between  the  fourth   and  fifth  magnitude. 
At  182  h.  it  was  increafed,  and  nearly  eqUal  to  0  Herculis  ;  but ' 
lefs  than  Q  and  J  ;   not  quite  of  the  fourth  magnitude. 

Dec.  1 1.  At  6  h.  and  8  h.  lefs  than  y  Lyrae,  and  brighter 
ilian  Q  and  |  Herculis.  At  8|-  h.  ^\  h.  and  i^l  h.  nearly 
equal  to,  though  rather  lefs  than  y. 

Dtc.  12.  At  5  h,  and  6  h.  ^learly  equal  to  7,  thougli  rather- 
lefs. 

Dec.  13.     At  51  h.  and  9I  h.  fomething  brighter  than  y, 

Dec.  14.     At  7  h.  and  8|  h.  rather  brighter  than  y. 

Dec.  17.  At  5!  h.  lefs  than  y  Lyra%  and  brighter  than 
S  and  t,  Herculis.     At  7I  h.  nearly  equal  to  y^  though  rather 

Dec, 


of  a  new  Varlalk  Star,  1 6  r 

Dec.  19.  At  9  h.  I  believe  It  was  brighter  than  7,  but  the 
weather  was  not  very  favourable. 

At  19  h.  little  lefs  than  y. 

Dec.  20.  At  55  h.  lefs  than  y  Ivvra,',  and  brighter  tliau 
5  and  I  Herculls.  At  6.|  h.  nearly  equal,  though  rather  lels 
than  y  Lyrct. 

Dec.  21.  At  8  h.  much  lefs  than  7,  and  confiderably 
brighter  than  ^Lyrae  ;  not  quite  of  the  fourth  magnitude. 

At  18  h.  a  little  brighter  than  ^  and  jc,  and  brighter  than  J 
Lyra^;  between  the  fourth  and  fifth  magnitude. 

Dec.  28.  At  6h.  lefs  than  7  and  brighter  than  5  Herculls  ; 
between  the  third  and  fourth  magnitude.  At  8  h.  nearly  equal 
to  Q  Herculls  ;  between  the  fourth  and  third  magnitude. 

1785,  Jan.  5.  At  5|h.  about  equal  to  ^Herculls;  fourth 
magnitude* 

Jan.  6.  At  5I  h.  bettveen  y  Lyrae  and  5  Herculls,  but  rather 
nearer  y.     At  8|  h.  It  feemed  a  little  brighter  than  y. 

From  the  above  ferles  of  obfervations  I  have  deduced  all  the 
conclufions  relative  to  the  eight  points  of  the  variation,  as  they 
are  flated  in  the  beginnmg  of  this  paper.  However,  as  at  firil  It 
•may  not  clearly  appear,  that  the  ftar  has  a  more  confiderable 
diminution  in  the  third  point  than  In  the  feventh.  It  will  not 
be  improper  to  add  a  few  words  relating  to  that  clrcumilancc  : 
for  proof  of  it,  therefore,  I  refer  to  an  attentive  coniparlfon  cA 
the  obfervations  of  Sept.  10.  Sept.  23.  Oct.  5-  and  6.  Ode, 
18  and  19.  &c.  correfponding  to  the  third  poliit  of  the  varia- 
tion with  thofe  of  Sept.  29  and  30.  Odi.  25,  Nov.  7  and 
19,  &c.  correfponding  to  the  feventh  point  of  the  varLa- 
tlon.  It  may  be  objefted,  that  in  fome  of  the  obfervations  of 
the  feventh  point,  the  ftar  might  have  become  flMl.more  di- 
minlfhed  in  the  Intermediate  hours  ;  but  this  is  not  probable^ 

Vol.  LXXV.  Y  btcauie 


i'62  Mr.  GooDRicKE*s  Obfervat'ions 

becaufe  in  that   point  the  flar  has  been  obferved  of  about  the 

fourth  magnitude  at  intervals  much  fhorter  than  in  the  third 

point,  fo  that,  if  it  had  continued  to  diminifli,  its  diminution 

would  have  proceeded  at  a  more  rapid  rate,  which  ftill  fhews 

that  there  is  at  leaft  a  difference  between  thefe  two  points. 

With  regard  to   the  period  of  the  variation,  it   is  evident 

from  a  collation  of  the  preceding  obfervations  in  a  coarfe  way, 

that  it  is  nearly  twelve  days  and  three  quarters.  To  determine  it 

with  greater  accuracy  is  a  fubje6t  of  confiderable  difficulty,  in 

the  prefent  cafe  ;  for  unlefs  we  can  obtain  very  exa6l  points  of 

comparifon,  the  period  would  come  out  erroneous,  efpecially 

if  deduced  from  intervals  confifting.  of  only  a  very  few  periods, 

as  is  the  cafe  here.     However,  as  I  have  been  able  to  obtain  a 

few  obfervations  of  the  middle  of  its  obfcuration  in  the  third 

point  accurate  enough  for  our  purpofe,  I  have  formed  the  fol« 

lowing  calculation. 

Times  of  the  middle  of  its  obfcuration 
in  the  third  point. 

1784,  oa.  6 
—  18 
oa.  18 


h. 

d. 

h. 

22J 

only  a  fingle  period  of 

12 

21 

221 

D° 

^- 

12 

17 

.;) 

two  periods, 

each  of 

12 

19 

—     3^ 

oa.   6 

-   31 

Hence  the  period  on  a  mean  is  1 2  1 9  :±: 
In  afcertaining  the  above  times,  I  attended  particularly  to 
the  neareft  obfervations  both  preceding  and  following.  In  the 
manner  above  ftated  the  period  may  alfo  be  deduced  from  the 
middle  of  its  obfcuration  in  the  feventh  point ;  but  as  thefe 
obfervations  are  not  fo  exaa  as  the  above,  I  Ihall  only,  as  a 

further 


of  a  new  Variable  Star,  16-' 

further  confirmation,  compare  two  of  the  mofl:  di^ant  of 
them,  v'i%.  Sept.  29.  22  h.  and  Nov.  20.  6  h.  which  interval  I 
find  contains  fix  periods,  each  of  12  d.  20  h.  ~. 

I  have  it  in  my  intention  to  pUrfue  the  fubje£l  further,  and 
when  I  have  got  a  fullicient  number  of  obfervations,  it  will 
be  eafy  to  determine  the  period  with  greater  exadnefs,  and 
alfo  at  the  fame  time  to  afcertain  the  other  particulars  of  the 
variation  with  more  precifion.  in  the  mean  while  I  wifli  that 
this  account  may  be  confidered  as  being  yet  imperfect ;  but  I 
was  induced  to  fend  it  in  its  prefent  ftate,  in  hopes  that  other 
aftronomers  may  contribute  by  their  obfervations  to  the  eluci- 
dation of  this  phicnomenon. 

As  /3  Lyrae  is  a  quadruple  ftar,  N°  3.  of  Mr.  Herschel's 
Vth  Clafs  of  Double  Stars  *,  I  was  defirous  to  fee  if  any  of 
the  fmall  flars  near  it  would  be  afFe(51:ed  by  its  different  changes  ; 
but  they  feemed  not  to  fuffcr  any  alteration,  either  when  it 
was  at  its  greatefl  or  at  its  leafl  brightncfs.  I  attended  to  this 
the  more  particularly  becaufe  the  lofs  of  the  flar's  light  was 
very  confiderable,  and  thephaenomenon  feemed  to  be  occafioned 
by  a  rotation  on  the  ftar's  axis,  under  a  fuppofition  that  there 
are  feveral  large  dark  fpots  upon  its  body,  and  that  its  axis  is 
inclined  to  the  earth's  orbit. 

I  muft  not  omit  mentioning  here  that  Mr.  Herschel, 
amongfl  thofe  ftars  v/hich  he  fuppofes  to  have  undergone  an 
alteration,  reckons  (3  or  y  Lyrae  ;  becaufe  he  obferved  that  y  was 
much  larger  than  (3,  whila  Flam^teed  marks  both  of  the 
fame  magnitude  -f*.  It  may  alfo  be  added,  as  fliewing  that  (3 
Lyrae  varied  in  former  times,  that  Hevelius,  in  his  Catalogue, 
differs  from  Flamsteed,  and  marks  y  of  the  third  magnitude. 


*  Phil.  Tranf.  for  1782,  p.  147. 
t  Phil.  Tranf.  for  17B3,   p.  256. 


Y  2  and 


1 64     Mr,  Goodricke's  Ohfervattons  of  a  new  Variable  Star, 

and  /S  of  between  the  fourth  and  third.  I  have,  however^ 
fome  doubts  whether  the  variation  of  this  ftar  does  not  entirely 
ceafe  or  become  lefs  vihble  in  certain  years.  Thefe  doubts  ari(e 
from  fome  obfervations  of  Cassini  in  Phil.  Tranf.  N""  y^^ 
p.  2198.  where  I  find  that  in  obferving  the  new  il:ar,  which, 
then  appeared  near  the  beak  of  the  Swan,  he  compared  it  very 
fr,equently  for  upwards  of  a  month  to  /S  and  y  Lyr^,  yet 
without  perceiving,  or  even  fufpe6i:ing,  that  /G  was  variable^ 
though  it  was  eafy  for  him  to  have  perceived  it,  if  th^  varia* 
tion  had  then  been  even  lefs  than  it  is  now.- 

I  am,  &c, 

JOHN  GOODRICKE* 


[     i65    T 


X.  On  the  Motion  of  Bodies  affecled  by  FrlBion.     By  the  Rev. 
Samuel   Vince,    yf.    M.     of   Cambridge;    CGmmtmicated  by 
Anthony  Shepherd,    D.  D.  F,  R.  S.   Plumia?2  Profejfor   of 
Ajlronotny  and  experimental  Philofophy  at  Cambridge. 

.  Read  November  25,  1784, 

THE  fubje6l  of  the  paper  which  I  have  now  the  honour 
of  prefentlng  to  the  Royal  Society,  feems  to  be  of  a 
very  confiderable  importance  both  to  the  practical  mechanic 
an4  to  the  fpeculatlve  philofopher ;  to  the  former,  as  a  know- 
ledge of  the  laws  and  quantity  of  the  fri6llon  of  bodies  in  motion 
upon  each  other  will  enable  him  at  firft  to  render  his  machines 
miore  perfect,  and  fave  him  in  a  great  meafure  the  trouble  of 
corre£ling  them  by  trials ;  and  to  the  latter,  as  thofe  laws 
will  furnifli  him  with  principles  for  his  theory,  which  when 
eflablifhed  by  experiments  will  render  his  conclufions  appli- 
cable to  the  real  motion  of  bodies  upon  each  other.  But,  how- 
ever important  a  part  of  mechanics  this  fubje^l  may  conflitute, 
and  however,  from  its  obvious  ufes,  it  might  have  been  ex- 
pe6led  to  have  claimed  a  very  confiderable  attention  both  from 
the  mechanic  and  philofopher,  yet  it  has,  of  all  the  other  parts 
of  this  branch  of  natural  philofophy,  been  the  mod  neglected. 
The  law  by  which  the  motions  of  bodies  are  retarded  by  fric- 
tion has  never,  that  I  know  of,  been  truly  eftabiilhed^ 
MusscHENBROEK  fays,  that  in  fmall  velocities  the  fridion  varies 
very  nearly  as  the  velocity,  but  that  in  great  velocities  the  fri£lion 
.increafes  ;  he  has  alfo  attempted  to  prove,  that  by  Increafing 
Z  the 


1 66  Mr,  ViiircE  on  the  Motion  of 

the  weight  of  a  body  the  fridlon  does  not  always  Increafc  exacftly 
in  the  fame  ratio;  and  that  the  fame  body,  if  by  changiiig  its 
pofition  you  change  the  magnitude  of  the  furface  on  which  it 
moves,  will  have  its  quantity  of  friction  alfo  changed.  Hel- 
SHAM  and  Ferguson,  from  the  fame  kind  of  experiments, 
have  endeavoured  to  prove,  that  the  fri6lion  does  not  vary  by 
changing  the  quantity  of  furface  on  which  the  body  moves ; 
and  the  latter  of  thefe  aflerts,  that  the  fridion  increafes  very 
nearly  as  the  velocity;  and  that  by  increafing  the  weight, 
the  friction  is  increafed  in  the  fame  ratio.  Thefe  different  con- 
clufions  induced  me  to  repeat  their  experiments,  in  order  to  fee 
how  far  they  were  conclulive  in  refpe(5l  to  the  principles  de- 
dticed  from  them :  when  it  appeared,  that  there  was  another 
caufe  operating  befides  friction,  which  they  had  not  attended 
to,  and  which  rendered  all  their  dedu£l:ions  totally  inconcluiive. 
Of  thofe  who  have  written  on  the  theory,  no  one  has  efta- 
blifhed  it  altogether  on  true  principles  :  Euler  (whofe  theory 
is  extremely  elegant,  and  which,  as  he  has  fo  fully  confidered 
the  fubje6t,  would  have  precluded  the  neceffity  of  offering  any 
thing  further,  had  its  principles  been  founded  on  experiments) 
fnppofes  the  fri6iion  to  vary  in  proportion  to  the  velocity  of  the 
body,  and  its  preflure  upon  the  plane,  neither  of  which  are 
true:  and  others,  who  have  imagined  that  friftion  is  a  uni- 
formly retarding  force  (and  which  conje61:ure  will  be  confirmed 
by  our  experiments),  have  ftill  retained  the  other  fuppofition, 
and  therefore  rendered  their  folutions  not  at  all  applicable  to 
the  cafes  for  which  they  were  intended.  I  therefore  endea- 
voured by  a  fet  of  experiments  to  determine, 

I  ft,  Whether  fri^ion  be  a  uniformiy  retarding  force, 

2dly,  The  quantity  of  fiidlion. 


Bodies  affeSed  by  FriBion,  .  167 

^dly,  IVheiher  the  fridVion  varies  in  proportiofi  to  the  prejfure 
ar  weight, 

4thlv,  Whether  the  JriBion  be  the  fame  on  whichever  of  its  fur- 
faces  a  body  moves. 

The  experiments,  in  which  I  was  affifled  by  my  ingenious 
friend  the  Rev.  Mr.  Jones,  Fellow  of  Trinity  College,  were  made 
with  the  utmoll:  care  and  attention,  and  the  feveral  refults 
agreed  fo  very  exa6ily  with  each  other,  that  I  do  not  fcrnple  to 
pronounce  them  to  be  conclufive. 

2.  A  plane  was  adjufted  parallel  to  the  horizon,  at  the  extre- 
mity of  which  was  placed  a  pulley,  which  could  be  elevated  or 
deprefled  in  order  to  render  the  firing  which  connecled  the 
body  and  the  moving  force  parallel  to  the  plane.  A  fcale  accu- 
rately divided  was  placed  by  the  fide  of  the  pulley  perpendi- 
cular to  the  horizon,  by  the  fide  of  which  the  moving  force 
defcended ;  upon  the  fcale  was  placed  a  moveable  flage,  which 
could  be  adjufled  to  the  fjpace  through  which  the  moving  force 
defcended  in  any  given  time,  which  time  was  meafured  by  a 
well  regulated  pendulum  clock  vibrating  feconds.  Every  thing 
being  thus  prepared,  the  following  experiments  were  made  to 
afcertain  the  law  of  fridlon.  But  let  me  firfl  obferve,  that  if 
fri6lion  be  a  uniform  force,  the  difference  between  it  and  the 
given  force  of  the  moving  power  mufl  be  alfo  uniform,  and 
therefore  the  -moving  body  muft  defcend  with  a  uniformly  ac- 
Cfclexated  velocity,  and  confequently  the  fpaces  delcribed  from 
the  beginning  of  the  motion  mufl  be  as  the  fquares  of  the 
times,  jufl  as  when  there  was  no  friction,  only  they  will  be 
diminifhed  on  account  of  the  fri£lion. 

3.  Exp.  I .  A  body  was  placed  upon  the  horizontal  plane, 
and  a  moving  force  applied,  which  from  repeated  trials  was  found 
to  defcend  52!  inckes  in  4'^  for  by  the  beat  of  the  clock  and 

7  the- 


1 68 .  ^'  Mr.  ViNCE  on  tie  MoUon  of 

the  found  of  tlie  moving  force  when  it  arrived  at  theflage..  the 
fpace  could  be  verj  accurately  adjufted  to  the  time  ;  tlie  ftage 
v/as  then   removed  to  that  point  to  which  the  moving  iorce 
v/ould  defcend  in  3'^,  upon  Aippohtion  that  the  ipaces  defcribed 
hy  tlie  moving  power  were  as  the  fquares  of  the  times ;  and  the 
fpace  was  found  to  agree  very  accurately  Vvith  the  time ;  the 
ftage  was  then   removed  to  that  point  to  which  the  moving 
force  ought  to  defcend  in  2'',  upon  the  fame  fuppofition,  and 
the  defcent  was  found  to  agree  exactly  with  the  time ;  iaftly, 
the  ftage  was  adjufled  to  that  point  to  which  the  moving  force 
ought  to  defcend  in   \'\  upon  the  fame  fuppofition,  and  the 
fpace  was  obferved  to  agree  with  the  time.     Now,  in  order  to 
find  whether  a  difference  in  the  time  of  defcent  could  be  ob- 
ferved, by  removing  the  ftage  a  little  above  and  below  the  pofi- 
tions  which  correfponded  to  the  above  times,  the  experiment 
was  tried,  and  the  defcent    was  always  found  too  foon  in  the 
former,  and  too  late  in  tlie  latter  cafe  ;  by  which  I  was  affured 
that  the  fpaces  Hrft  mentioned  correfponded   exactly    to   the 
times.    And,  for  the  greater  certainty,  each  delcent  was  repeated 
eight  or  ten   times.;  and  every  caution  ufed  in  this  experiment 
was  alfo  made  ufe  of  in  all  the  folio  wins;. 

Exp.  2,  A  fecond  body  was  laid  upon  the  horizontal  plane, 
and  a  moving  force  applied  which  defcended  41 1  inches  in  3''''  ; 
the  ftage  was  then  adjufted  to  the  fpace  correfponding  to  z'\ 
upon  fuppofition  that  the  fpaces  defcended  through  were  as  the 
fquares  of  the  times,  and  it  was  found  to  agree  accurately  with 
the  time  ;  the  ftage  was  then  adjufted  to  the  fpace  correfpond- 
ing to  i^\  upon  the  fame  fuppofition,  and  it  was  found  to  agree 
with  the  time. 

Exp.  3.  A  third  body  was  laid  upon  the  horizontal  plane,  and 
amoving  force  applied,  which  defcended  59^  inches  in  4'^;  the 

ftage 


bodies  qff'ecied  by  Friolf on*  '  '        l6^ 

flage  Was  then  adjufted  to  the  fpacp  conelponding  to  3'',  upoti 
iuppofitioii  that  the  fpaces  defcended  through  were  as  the 
fquares  of  the  times,  and  it  was  found  to  agree  with  the  time  ; 
<the  ftage  was  then  adjufled  to  the  fpace  correfponding  to  2'% 
upon  the  fame  fuppofition,  and  it  was  found  to  agree  with  the 
time ;  the  ftage  was  then  adjufted  to  the  fpace  correfponding 
to  i'\  and  was  found  to  agree  with  the  time. 

Exp.  4.  A  fourth  body  was  then  taken  and  laid  upon  the 
horizontal  plane,  and  a  moving  force  applied,  which  defcended 
'^^  inches  in  4^';  the  ftage  was  then  adjufted  to  the  fpace 
through  which  it  ought  to  defcend  in  3'',  upon  fuppofition 
that  the  fpaces  defcended  through  were  as  the  fquares  of  the 
times,  and  it  was  found  to  agree  with  the  time ;  the  ftage  was 
then  adjufted  to  the  fpace  correfponding  to  2^\  upon  the  fame 
fuppofition,  and  was  found  to  agree  with  the  time ;  laftly,  the 
ilage  was  adjufted  to  the  fpace  correfponding  to  i'\  and  it  was 
found  to  agree  exactly  with  the  time. 

Befides  thefe  experiments,  a  great  number  of  others  were 
ttiade  with  hard  bodies,  or  thofe  whofe  parts  fo  firmly  cohered 
as  not  to  be  moved  inter  fe  by  the  fri£lion  ;  and  in  each  experi- 
ment bodies  of  very  different  degrees  of  friclion  were  chofen, 
and  the  refults  all  agreed  with  thofe  related  above ;  we  may 
therefore  conclude,  that  thefriSlion  of  hard  bodies  in  motion  is  a 
uniformly  r  etar  ding  for  ce^ 

But  to  determine  whether  the  fame  was  true  for  bodies  when 
covered  with  cloth,  woollen,  &c.  experiments  were  made  in 
■order  to  afcertain  it ;  when  it  was  found  in  all  cafes,  that  the 
retarding  force  Increafed  with  the  velocity  j  but,  upon  covering 
bodies  with  paper,  the  confequences  were  found  to  agree  with 
thofe  related  abovft 

Vol.  LXXV,  Z  4.  Having 


I  "o  M'\  V  J  NCE  on  the  Mouon  of 

4,  Mavliig  proved  that  the  retarding  force  of  all  hard  bodies 
ariiing  trom  trittion  is  luiiform,  tlie  quantity  of  fridion,  con- 
fidered  as  equivalent  to  a  weight  without  inertia  drawing  the 
body  on  the  horizontal  plane  backwards,  or  a<fling  contrary  to 
the  moving  force,  may  be  immediately  deduced  from  the  fore- 
going experiments.  For  let  M  =  the  moving  force  expreffed  by 
its  weight;  Fi=the  fricflion  ;  W=rthe  weight  of  the  body 
upon  the  iiorizontal  plane;  S  =  the  fpace  through  which  the 
moving  force  defcended  in  the  time  t  expreHed  in  fecotids  ; 
r=i6-j-a  feet;  then  the  whole  acceitrative  force  (the  force  of 

gravity  being  unity)  will  be  ^^  7"     y  hence,  by  the  laws  of  uni* 
formly    accelerated      motions,      ■  ,  -  x  rr  —  S,    confequently 


F  —  M  —  -^  "^  .  z^  .   To  exemplify  this,  let  us  take  the  cafe  of  the 

laft  experiment,  where  Mz=7,  Wr:  25I,  5=4/^  feet,  i^^^'i 

hence  F=  7 -^^4^7^  =  6.417  ;  confequently  the  fridion  was 

to  the  weight  of  the  rubbing  body  as  6.4167  to  25.75.  ^'^^ 
the  great  accuracy  of  determining  the  friction  by  this  method  is 
manifefl:  from  hence,  that  if  an  error  of  t  inch  had  been  made 
in  the  defcent  (and  experiments  carefully  made  may  always  de- 
termine the  fpace  to  a  much  greater  exadnefs)  it  would  not 
have  affeded  the  conclufion  -^;-o-dth  part  of  the  whole. 

5.  We  come  in  the  next  place  to  determine,  whether  fric- 
tion, cceteris  paribus,  varies  in  proportion  to  the  weight  or 
preflure.  Now  if  the  whole  quantity  of  the  fridion  of  a  body, 
meafured  by  a  weight  without  Inertia  equivalent  to  the  fridion 
drawing  the  body  backwards,  increafes  in  proportion  to  its 
weight,  it  is  manifefl:,  that  the  retardation  of  the  velocity  of 
the  body  arifing  from  the  fridion  will  not  be  altered;  for  the 
7  retardation 


Boiiies  iijfl'tteci  by  Fricficn,  I  '^«  i 

,     .  .  Qiiantity  of  fiii^ion       i  -.-it. 

retardation  vanes  as  -^ — ~ — 7: ;  hence,  it  a  body  be  r>ut 

Quantity  ot  matter  '  /  r    *• 

ill  motion  npon  the  horizontal  plane  by  any  moving  force,  if 
both  the  weight  of  the  body  and  the  moving  force  be  increafed 
in  the  fame  ratio,  the  acceleration  ariling  from  that  moving 
force  will  remain  the  fame,  becaufe  the  accelerative  force  varies 
as  the  moving  force  divided  by  the  whole  quantity  of  matter, 
and  both  are  increafed  in  the  fame  ratio  ;  and  if  the  quantity 
of  fri£^ion  increafes  alio  as  the  weight,  then  the  retardation 
arifing  from  the  fri6lion  will,  from  what  has  been  faid,  remain 
the  fame,  and  therefore  the  whole  acceleration  of  the  body  will 
not  be  altered  ;  confequently  the  body  ought,  upon  this  fuppo- 
iitlon,  fliill  to  defcrlbe  the  famefpace  in  the  fame  time.  Hence, 
by  obferving  the  fpaces  defcribed  in  the  fame  time,  when  both 
the  body  and  the  moving  force  are  increafed  in  the  fame  ratio, 
we  may  determine  whether  the  fri6lion  increafes  in  proportion 
to  the  weight.  The  following  experiments  were  therefore 
made  in  order  to  afcertain  this  matter. 

Exp.  I.  A  body  weighing  10  oz.  by  a  moving  force  of  4  oz. 
defcribed  in  2^^  a  fpace  of  5 1  inches ;  by  loading  the  body  with 
10  oz.  and  the  moving  force  with  4  oz.  it  defcribed  ^6  inches 
in  2";  and  by  loading  the  body  again  with  10  oz.  and  the 
moving  force  with  4  oz.  it  defcribed  61  inches  in  2^\ 

Exp.  2.  A  body,  whofe  weight  was  16  oz.  by  a  moving 
force  of  5  oz.  defcribed  a  fpace  of  49  inches  in  3'^;  and  by 
loading  the  body  with  64  oz.  and  the  moving  force  with  20  oz. 
the  fpace  defcribed  in  the  fame  time  was  64  inches. 

Exp.  3.  A  body  weighing  6  oz.  by  a  moving  force  of  2|  oz., 
defcribed  28  inches  in  2'^  \  and  by  loading  the  body  with  24 
oz.  and  the  moving  force  with  10  oz.  the  fpace  defcribed  in  the 
fame  time  was  54  inches. 

Z  2  Exp. 


1^2  Mr.  \ ijsCE,  on  the  Motion  ef' 

ExF.  4,  A  body  weighing  8  oz.  by  a  moving  force  of  4  oZo 
defcribed  33I  inches  in  2'^;  and  by  loading  the  body  with  8 
oz.  and  the  moving  force  with  4  oz.  the  fpace  defcribed  in  the 
fame  time  was  47  inches. 

Exp.  5.  A  body  whofe  weight  was  9  oz.  by  a  moving  force  of-" 
4I  oz.  defcribed  48  inches  in  2^^;  and  by  loading  the  body  with. 
9  oz.  and  the  moving  force  with  4i  oz.  the  fpace  defcribed  in 
the  fame  time  was  60  inches. 

Exp.  6.  A  body  weighing  10  oz.  by  amoving  force  of  3  oz. 
defcribed  20  inches  in  2/'',  by  loading  the  body  with  10  oz.. 
and  the  moving  force  with  3  oz.  the  fpace  defcribed  in  the  fame- 
time  was  31  inches ;  and  by  loading  the  body  again  with  30- 
Qz.  and  the  moving  force  with  9,  oz.  the  fpace  defcribed  was. 
34  inches  in  z^/. 

From  thefe  experiments,  and  many  others  which  it  Is  not 
neceflary  here  to  relate,  it  appears,  that  the  fpace  defcribed  is 
always  increafed  by  increafing  the  weight  of  the  body  and  the 
acceleratlve  force  in  the  fame  ratio;  and  as  the  accelerationr 
ariiing  from  the  moving  force  continued  the  fame,  it  is  manifeft, 
that  the  retardation  arifing  from  the  fridion  muft  have  beenr 
diminifhed,  for  the  whole  acceleratlve  force  muft  have  been  in- 
creafed on  account  of  the  increafe  of  the  fpace  defcribed  in  the 
fame  time  ;  and  hence  (as  the  retardation  from  friction  varies  as 

Quantity  of  friftion  \      ,-,  ..  r  r    'ct'        •  r       •  r  r         u' 

~ — T^ — ^ the  quantity  of  fnciton  increales  m  a  lejs  ratio 

Quantity  ot  matter  J  i  ^    ^  -^  -^  -^ 

than  the  quantity  of  matter  or  weight  of  the  body. 

6.  We  come  now  to  the  laft  thing  which  it  was  propofed  ta 
determine,  that  is,  whether  the  fri£lion  varies  by  varying  the  fur- 
face  on  which  the  body  moves.  Let  us  call  two  of  the  furfaces 
A  and  ^,  the  former  being  the  greater,  and  the  latter  the  lels. 
Now  the  weight  on  every  given  part  of  a  is  as  much  greater 
2  than 


B^dth  affccfcd  by  Fn'^lion,  1 73 

than  the  weight  on  an  equal  part  of  A,  as  A  is  greater  than  a  ; 
if  therefore  the  fridtion  was  in  proportion  to  the  weiglit,  CiVte^ris 
paribus^  it  is  inanifefl,  that  the  fridion  on  a  would  be  equal  to 
the  friction  on  A,  the  whole  fri£lion  being,  upon  fuch  a  fuppo- 
fition,  as  the  weight  on  any  given  part  of  each  furface  multi- 
plied into  the  number  of  fuch  parts  or  into  the  whole  area, 
which  produdls,  from  the  proportion  above,  are  equal.  But 
from  the  laft  experiments  it  has  beeji  proved,  that  the  fridlion 
on  any  given  furface  increafes  in  a  lefs  ratio  than  the  weight ; 
confequently  the  fridion  on  any  given  part  of  ^  has  a  lefs  ratio 
to  the  fridion  on  an  equal  part  of  A  than  A  has  to  a^  and 
hence  the  friftion  on<^  is  lefs  than  the  friflion  on  A,  that  is, 
the  fmalleft  furface  has  always  the  leaft  fridion.  But  as  this 
conciufion  is  contrary  to  the  generally  received  opinion,  I  have- 
thought  it  proper  to  confirm  the  fame  by  a  fet  of  experiments. 
But  before  I  proceed  to  relate  them,  I  will  beg  leave  tC'recom-^ 
mend  to  thofe,  who  may  afterwards  be  induced  to  repeat  them, 
the  following  cautioijis,  which  are  extremely  neceflary  to  be 
attended  to.  Great  care  muft  be  taken  that  the  two  furfaces- 
have  exactly  the  fame  degree  of  roughnefs ;  in  order  ta  be 
certain  of  which,  fuch  bodies  mufl  be  chofcn  as  have  no  knots 
in  them,  and  whofe.  grain  is  fo  very  regylar  that  when  the 
two  furfaces  are  planed  with,  a  fine  rough  plane,  their  rough- 
nefs may  be  the  fame,  which  will  not  be  the  cafe  if  the  body 
be  knotty,  or  the  grain  irregular,  or  if  it  happens  not  to  run 
in  the  fame  direction  on  both  furfaces.  When  you  cannot  de- 
pend on  the  furfaces  having  the  fame  degree  of  roughnefs,  the 
beft  way  will  be  to  pafte  Ibme  fine  rough  paper  on  each  fur- 
face, which  perhaps  will  give,  a  more,  equal  degree  of  rough- 
nefs than  can  be  obtained  by  any  other  method.  Now  as  the- 
proof  which  I  have  already  given  depends  only  on  the  motion'. 

of^ 


!^4-  ^'^'''  ViNCE  on  the  Motion  of 

of  t'he  body  upon  the  fame  furface^  it  is  not  liable  to  any  inac- 
curacy of  tbe  kind  which  the  preceding  cautions  have  been 
given  to  avoid,  nor  indeed  to  any  other,  and  therefore  it  niufl 
be  perfectly  conclufive.  In  the  following  experiments  the 
cautions  mentioned  above  were  carefully  attended  to. 

Exp.  I.  A  body  was  taken  whofe  flat  furface  was  to  its  edge 
as  22  :  9,  and  with  the  fame  moving  force  the  body  defcribed 
on  its  flat  (ide  33!  inches  in  2^^,  and  on  its  edge  47  inches  in 
the  fame  time. 

Exp.  2.  A  fecond  body  was  taken  whofe  flat  furfaCe  was  to 
Its  edge  as  32  :  3,  and  with  the  fame  moving  force  it  defcribed 
on  its  flat  fide  32  inches  in  2'\  and  on  its  edge  it  defcribed  37 1 
inches  in  the  fame  time. 

Exp.  3.  1  took  another  body  and  covered  one  of  its  furfaces, 
whofe  length  was  9  inches,  with  a  fine  rough  paper,  and  by 
applying  a  moving  force,  it  defcribed  25  inches  in  2^^ ;  I  then 
took  off  fome  paper  from  the  middle,  leaving  only  4-  of  an  incli 
at  the  two  ends,  and  with  the  fame  moving  force  it  defcribed 
40  inches  in  the  fame  time. 

Exp.  4.  Another  body  was  taken  which  had  one  of  its  fur- 
faces,  whofe  length  was  9  inches,  covered  with  a  fine  rough 
paper,  and  by  applying  a  moving  force  it  defcribed  42  inches 
in  2^^ ;  fome  of  the  paper  was  then  taken  off  from  the  mid- 
dle, leaving  only  i^-  inches  at  the  two  ends,  and  with  thef^me 
moving  force  it  defcribed  54  inches  in  2'';  1  then  took  off 
more  paper,  leaving  only  I  of  an  inch  at  the  two  ends,  and 
the  body  then  defcribed,  by  the  fame  moving  force,  60  inches 
in  the  fame  time. 

In  the  two  laft  experiments  the  paper  which  was  taken  off 
the  furface  was  laid  on  the  body,  that  its  weight  might  not  be 
altered. 

Exp. 


B',d:es  affi'cUd  by  FriClLn,  17^ 

Kxp.  5.  A  body  was  taken  whole  fiat  rurface  was  to  its  rdge 
as  30  :  17  ;  ihcfiat  llde  was  laid  upon  the  horizontal  phme,  a 
moving  force  was  applied,  and  the  flage  was  fixed  in  order  to 
frop  the  moving  iorce,  in  confcquence  of  which  the  body 
would  then  go  on  with  the  velocity  acquired  until  the  fridion 
had  deilroyed  all  its  motion;  when  it  appeared  from  a  mean  of 
12  trials  that  the  body  moved,  after  its  acceleration  cealed, 
5^  inches  before  it  flopped.  The  edge  was  then  applied,  and  the 
moving  force  defcended  through  the  fame  fpace,  and  it  was 
found,  from  a  mean  of  the  fame  number  of  trials,  that  the 
fpace  defcribed  was  7^  inches  before  the  body  lofl  all  its  motion, 
after  it  ceafed  to  be  accelerated. 

Exp.  6.  Another  body  was  then  taken  whofe  fiat  furface  was 
to  its  edge  as  60  :  19,  and,  by  proceeding  as  before,  on  the  flat 
lurface  it  defcribed,  at  a  mean  of  1 2  trials,  54.  inches,  and  on 
the  edge  6a  1.  inches,  before  it  flopped,  after  the  acceleration 
ceafed. 

Exp.  7.  Another  body  was  taken  whofe  flat  furface  was  to 
its  edge  as  26  :  3,  and  the  fpaces  defcribed  on  thefe  two  fur- 
faces,  after  the  acceleration  ended,  were,  at  a  mean  of  10 
trials,  4I-  and  7-%.  inches  refpedively. 

From  all  thefe  different  experiments  it  appears,  that  the 
fmallefl  furface  had  always  the  leaf!  fri£lion,  which  agrees, 
with  the  confequence  deduced  from  the  conlideration  that  the 
friclion  does  not  increafe  in  fo  great  a  ratio  as  the  weight ;  we 
may  therefore  conclude,  that  the  friSlion  of  a  body  does  not  con- 
tinue the  fame  when  it  bus  different  furf  aces  applied  to  the  plane  on 
which  it  moves ^  but  that  the  fmalleji furface  will  have  the  leaft' 
fri6lion, 

7.  Having  thus  eflablifhed,  from  the  mof^  declfive  experi- 
ments, all  that  I  propofed  relative  to  fridion,  I  think  it  proper,. 

before 


-176  "Mr.  VlNCE  071  the  Motion  of 

before  I  conclude,  to  give  the  refult  of  my  examination  into 
the  nature  of  the   experiments  which    have  been    made  by 
others ;  wliich  were  repeated,  in  order  to  fee  how  far  they 
were  conclufive  in  refpe(fl  to  the   principles  which  have  been 
deduced  from  them.     The  experiments  which  have  been  made 
by  all  the  authors  that  I  have  feen,  have  been  thus  inftitutedr 
To  find  what  moving  force  would  ^^  put  a  body  at  reft  in 
♦motion  :  and  they  concluded  from  thence,  that  the  accelerative 
force  was  then  equal  to   the  fridion  ;  but  it  is  manifeft,  that 
-  any  force  which  will  put  a  body  in  motion  muft  be  greater 
than  the  force  which  oppofesits  motion,  otherwife  it  could  not 
overcome  it ;  and  hence,  if  there  were  no  other  objeflion  than 
this,  it  is  evident,  that  the  fri6lion  could  not  be  very  accurately 
obtained ;  but  there  is  ancHrher  obje£tion  which  totally  deftroys 
the  experiment  fo  far  as  it  tends  to  fhow  the  quantity  of  fric- 
tion, which  is  the  ftrong  cohefion  of  the  body  to  the  plane 
when  it  lies  at  reft ;  and  this  is  confirmed  by  the  following 
experiments,      ift,  A  body  of  'I2i  oz.  was  laid  upon  an  hori- 
zontal plane,  and  then  loaded  with  a  weight  of  8  lb.  and  fuch 
a  moving  force  was  applied  as  would,  when  the  body  was  juft 
put  in  motion,  continue  that  motion  without  any  acceleration, 
in  which  cafe  the  frldion  muft  be  juft  equal  to  the  accelerative 
force.  The  body  was  then  ftopped,  when  it  appeared,  that  the  fame 
moving  force  which  had  kept  the  body  in  motion  before,  would 
not  put  it  in  motion,  and  it  was  found  neceflary  to  take  off 
4I  oz.  from  the  body  before  the  fame  moving  force  wou^  put 
it  in  motion ;  it  appears,  therefore,  that  this  body,  when  laid 
upon  the  plane  at  reft,  acquired  a  very  ftrong  cohefion  to  it. 
idly,  A  body  whofe  weight  was  1 6  oz.  was  laid  at  reft  upon  the 
horizontal  plane,  and  it  was  found  that  a  moving  force  of  6  oz. 
^'ould  juft  put  it  in  motion ;  but  that  a  moving  force  of  4  oz. 

wouIJ 


Bodies  ajfeSii'd  hy  FrtSilon,  177 

would i  when  It  was  jufl:  put  in  motion,  continue  that  motion 
without  any  acceleration,  and  therefore  the  accelerative  force 
muft  t/jen  have  been  equal  to  the  friction,  and  not  when  tli& 
moving  force  of  6  oz.  was  applied. 

From  thefe  experiments  therefore  it  appears,  how  very 
conliderable  the  cohefion  was  in  proportion  to  the  fri£lion  when 
the  body  was  in  motion  ;  it  being,  in  the  latter  cafe^  almoir. 
I,  and  in  the  former  it  was  found  to  be  very  nearly  equal  to 
the  whole  fridlon.  All  the  conclufions  therefore  deduced  from 
the  experiments,  which  have  been  inflituted  to  determine  the 
fridion  from  the  force  ncceflary  to  put  a  body  in  motion  (and  I 
have  never  feen  any  defcribed  but  upon  fuch  a  principle)  have 
manifeftly  been  totally  falfe ;  as  fuch  experiments  only  {hew 
the  refiftance  which  arifes  from  the  cohefion  and  friction  con- 
jointly. 

8.  I  (hall  conclude  this  part  of  the  fubjcfl  with  a  remark 
upon  Art.  5.  It  appears  from  all  the  experiments  which  I  have 
made,  that  the  proportion  of  the  increafe  of  the  fri£lion  to  the 
increafe  of  the  weight  was  different  in  all  the  different  bodies 
which  were  made  ufe  of;  no  general  rule  therefore  can  be  efta- 
blilhed  to  determine  this  for  all  bodies,  and  the  experiments 
which  I  have  hitherto  made  have  not  been  fufficient  to  deter- 
mine it  for  the/ame  body.  At  fome  future  opportunity,  when 
I  have  more  leifure,  I  Intend  to  repeat  the  experiments  in  order 
to  eftabliih,  in  fome  particular  cafes,  the  law  by  which  the 
quantity  of  friction  increafcs  by  increafmg  the  weight.  Leaving 
this  fubje<St  therefore  for  the  prefent,  I  (hall  proceed  to  eftablllK 
a  theory  upon  the  principles  which  we  have  already  deduced 
from  our  experiments. 


V«L.  LXXV.  A  A  PRO- 


i  '-S  Mr,  ViNCE  on  the  Motion  of 


PROPOSITION      !► 


Let  c^  f,  g,  (tig.  i.)  reprefent  either  a  cylinder^  or  that  circular 
Jecfion  of  a  body  on  which  it  rolls  down  the  inclined  plane  CA  im 
coufeqiience  of  its  fridfion^  to  find  the  time  of  defcetit   and  tht 
number  of  revolutions. 

As  it  has  been  proved  in  Art.  5.  that  the  fri£lion  of  a  body^ 
does  not  iiicreafe  in  proportion  to  its  weight  or  prefllire,  we 
cannot  therefore,  by  knowing  the  friction  on  any  other  plane,, 
determine  the  friction  on  CA  ;  the  friction  therefore  on  CA  can 
only  be  determined  by  experiments  made  upon  that  plane,  that 
is,  by  letting  the  body  defcend  from  red:,  and  obferving  the 
fpace  dclcribed  in  the  firft  fecond  of  time ;  call  that  fpace  a^. 
and  then,  as  by  Art»  3.  friction  is  a  uniformly  retarding  force, 
the  body  muft  be  uniformly  accelerated,  and  confecjuently  the; 

/AC 

whole  time  of  defcent  in  feconds  will  be  =  \/— .    Now  to  deter-- 

mine  the  number  of  revolutions^  let  j  be  the  center  of  ofcillatioii^^ 
to  the  point  of  fufpenfion  a  *  j  then,  becaufe  no  force  acting  at  a 
can  affe£t  the  motion  of  the  point  j,  that  point,  notwithftanding; 
the  action  of  the  fri£tion  at  a,  will  always  have  a  motion  pa- 
rallel to  CA  uniformly  accelerated  by  a  force  equal  to  that 
with  which  the  body  would  be  accelerated  if  it  had  no  friction ;. 
hence,  if  2;;^/ =  3.2-3- feet,  the  velocity  acquired  by  the  point  s 

iii'tKe'firil:  fecond  will  be  =  "^^^.  -  ;  now  the  excefs  of  the  ve- 

*  a  and  s  are  not  fixed  points  in  the  body,  but  the  former  always  repreffenti 
that  point  of  the  body  in  contaft  with  the  plane,  and  the  latter  the  correfponding 
■  center  of  ofciIlation» 

2  loeity 


bodies  aj^ediei  hy  TriBlon.  i  ^j  ^j 

Joclty  df  the  point  s  above  that  of  r  (r  being  the  center)  is  ma- 
n.ifeftly  the  velocity  with  which  s  is  carried  about  r;  hence  the 

velocity  of  s  about  the  center  ——-t\ tazn — - — y— _  ^ ^.^ , 

•^  UA  CA  ' 

r  ^\  ^  2WXCI3-2^XCA       2?«Xr^xCB— 2«X''^XCA 

confequentiv  rs  \  ra  w  — r : — ^ — iJiJ: 

^  J  CA  ;.fXCA 

p  the  velocity  with  which  a  point  of  the  circumference  is  car- 
ried about  the  center,  and  which  therefore  express  the  force 
which  accelerates  the  rotation ;  now  as  za  exprefles  the  accele- 
rative  force  of  the  body  down  tiie  plane,  and  the  fpaces  de- 
fcribed  in  the  fame  time  are  in  proportion  to   thofe  forces,  we 

have  2  a  :  CA  ::  ■  ttt— '• — - 

the  fpace  which  any  point  df  the  circumference  defcribes  about 
the  center  in  the  whole  time  of  the  body's  defcent  down  CA  ; 
which    being    divided    by    the    circumference    p  x  ra    (where 

^  =  6.282  Sec.)  will  p-ive^- ^ for  the  whole  number 

of  revolutions  required. 

Cor.  I.  If  a  X  CA  =  ;«  x  BC,  the  number  of  revolutions  —  o, 
and  therefore  the  body  will  then  only  Aide ;  confequentlj/  the 
friction  vanifhes. 

Cor.  2.  Let  a^r's^  (fig.  2.)  be  the  next  polltion  of  ars,  and 
draw  /  r^^  parallel  to  sa,  then  will  j'/  reprefent  the  retardation 
of  the  center  r  arifing  from  friction,  and  a^  b  will  reprefent  the 
acceleration  of  a  point  of.  the  circumference  about  its  center; 
hence  the  retardation  of  the  center  :  accetef^tion  of  the  cir- 
cumference about  the  center  ::  s't  :  a' b  ::  (by  fim.  a's) 
ir'  :  hr'  ::  rs  \  ra. 

Cor.  3.  If  ^^  coincides  with  /?,  the  body  does  not  y7/^<?  but 
only  roll;  now  in  this  cafe  s s'  :  rr'  \\  a s\  ar\  but  as  ^ s'  and 
r  r'  reprefent  the  ratio  of  the  velocities  of  the  points  s  and  r, 

A  a  '2  they 


1 8o  Mr.  ViNCE  on  the  Motion  of 

thev  will  be  to  each  other  as  '-^^ :  2?  or  as  m  x  CB:  a  x  CA; 

hence,     when   the   body   ro//s  Without  Jli ding ^    a  s  :  a  r  y,  m  x 
CB  :  ^  X  CA. 

Cor,  4.  The  tune  of  dcfcent  down  CA  is=^  sJ' —  »   but  by 

the  lad  Cor.  when  the  body  rolls  without  Jli J/ nq;.  ^/  =  ' — r-  • 


hence  the  tune  of  defcent  in  that  cafe  —AC  4/ ^^^7^,  ;  now 

\  OT  X  r^  X  BC 


the   tune  of  defcent,  if  there  were   no  friclion,  would   be  = 

AC 
-7  ,  hence  the  time  of  defcent,  wlien  the  body  rol/s  with- 

^w  X  BC  ^ 

out ^fliding  :  time  of  free  defcent  ::  K^sa  :  \/r  a. 

Cor,  5.  By  the  laft  Cor.  it  appears,  that  when  the  body  juft  rolls 
without  Jli ding,  or  when  the  fridion  is  juft  equal  to  the  accelera- 

tiv€  force,  the  time  of  defcent  =AC\J .,,,  ;  now  it  is  ma- 

'  \m  xra  X  BCl 

nifeft,  that  the  time  of  defcent  will  continue  the  fame,  if  the 
friction  be  increafed,  for  the  body  will  ftill  freely  roll,  as  no 
increafe  of  the  fridion  ading  at  a  can  affect  the  motion  of  the 
point  J. 

If  the  body  be  projetfled  from  C  with  a  velocity,  and  at  the 
fame  time  have  a  rotatory  motion,  the  time  of  defcent  and 
the  number  of  revolutions  may  he  determined  from  the  com- 
mon principles  of  uniformly  accelerated  motions,  as  we  have 
already  inveftigated  the  accelerative  force  of  the  body  down 
the  plane  and  of  its  rotation  about  its  axis ;  it  feems  therefore, 
xjnneceilary  to  lengthen  out  this  paper  with  the  iuvefligations* 


p  s  a- 


BoJics  aJfeShd  by  Friciion.  i  §  I 


PROPOSITION       II. 

Let  the  My  be  pro'iecied  on  an  horizontal  plane  LM  (fig.  j.) 
with  a  given  velocity  to  determine  the  fp.ice  through  which  the 
jbody  ivill  move  bejore  it  JtopSy  or  bcjore  its  motion  becomes  latijorni. 

Case  I.  i.  Siippofe  the  body  to  have  no  rotatory  motion 
when  it  begins  to  move;  and  let  ^  =  the  velocity  of  projedioU' 
per  lecond  measured  hi  feet,  and  let  the  retarding  force  of  the 
fri£lion  of  the  body,  meal u red  by  the  velocity  of  the  body 
which  it  can  deftroy  in  one  fecond  of  time,  be  determined  by 
experiment  and  called  F,  and  let  ,v  be  the  fpace  through  which 
the  body  would  move  by  the  time  its  motion  was  all  deilroyed 
when  projeded  with  the  velocity  a,  and  retarded  by  a  force  F ; 
then,  from   the   principles  of  uniformly  retarded  motion,  a=i 

2, 

— ,  and   if  /^rtime  of   defcribing   that  fpace,    we  have   /  — 
-  ,  and  hence  the  fpace  defcribed  in   the   firft  fecond  of  time 

= .     Now  it  is  manifeil,  that  when  the  rotatory  motion 

of  the  body  about  its  axis  is  equal  to  its  progreflive  motion,  the 
point  a  will  be  carried  backwards  by  x\\q  farmer  motion  as  much 
as  it  is  carried  forwards  by  the  latter  y  confequently  the  point  of 
eonta(ft  of  the  body  with  the  plane  will  then  have  no  motion 
in  the  direction  of  the  plane,  and  hence  the  fricflion  will  at 
that  inftant  ceafe,  and  the  body  will  continue  to  roll  on  uni- 
formly without  Jliding  with  the  velocity  which  it  has  at  that 
point.  Put  therefore  s^the  fpace  defcribed  from  the  com- 
mencement of  the  motion  till  it  becomes  uniform,  then  the 
body  being  uniformly  retarded,  the  fpaces  from  the  end  of 
7  the: 


V' 


"1^2  Mr,  ViNCE  on  the  Motion  of 

the   motion    vary   as   the   fqnares    of   the    velocities,    hence 

2  2 

-^'.  a   (^.\  I  :  2F)  ::  -T.  ~  z  :  <2*  -  2Fs  =  fquare  of  the  progref- 

five  velocity  when  the  motion  hecomes  uniform  ;   therefore  the 

velocity  deflroyed  by  friction  ~a  —  \/ a^  —  2F2 ;  hence,  as  the 
velocity  generated  or  deflroyed  in  the  fame  time  is  in 
proportion    to    the    force,    we    have    by     Cor.    2,    Prop.    i. 


}•  s  :  r  a  •.-.a  —  s/a"  ~  2bz  \  -  X  a  —  s/a'' —  z¥z    the   velocitv   of 

r  i  "' 

tiie  circumference  efg  generated  about  the  center,  conlequently 


s/a^  —  2Fz~  — X  a  — s/ii^  —  2b'z,  and  hence  z—  ^ 

r  s  as    X  2F 

the  Ipace  which  the  body  defcribes  before  the  motion  becomes 
'uniform. 

2.  If  w^e  fubftitutethis  value  of  z  into  the  expreffion  for  the 

velocity,  we  (liall  have  a  x  -  for  the  velocity  of  the  body  when 

its  motion  becomes  uniform ;  hence  therefore  it  appears-,  that 
the  velocity  of  the  body,  when  the  fr](5lion  ceafes,  will  be  the 
fame  whatever  be  the  quantity  of  the  fri6lion.  If  the  body  be 
the  circumference  of  a  circle,  it  will  always  lofe  half  the  ve- 
locity before  its  motion  becomes  uniform. 

Case  II.  i.  Let  the  body,  befides  having  a  progreffive 
velocity  in  the  direction  LM  (fig.  3.)  have  alio  a  rotatory  mo- 
tion about  its  center  in  the  diredlion  gfe,  and  let  v  reprefent 
the  initial  velocity  of  any  point  of  the  circumference  about  the 
center,  and  fuppofe  it  firft  to  be  lefs  than  a  ;  then  fri«5lion  being 
a  uniformly  retarding  force,  no  alteration  of  the  velocity  of 
the  point  of  contad  of  the  body  upon  the  plane  can  affecl  the 
^quantity  of  fridion  ;  hence  the  progreffive  velocity  of  the  body 
Hvill  be  the  fame  as  before,  and  confequently  the  rotatqry  velo-^ 

city 


Bodies  ajfe6ied  hy  Fridlion,  i8'i>' 

city  generated  by  fridion  will  alio  be  the  fame,  to  which  if  wc 
add  the  velocity  about  the  center  at  the  beginning  of  the  mo- 
tion, we  fhall  have  the  whole  rotatory  motion  ;  hence  there- 


ra       ~~' -  — __- 

fore,  v  +  —  X  a  —  \/ a  —  2F2;  =  ^a^  —  2F2,    confequently 


«*  X  as^—  V  Xrs  +  ^x  ri 


2F  X  <3i 

comes  uniform. 


the  fpace  defcribed  before  the  motion  be- 


2.  If  this  value  of  z  be  fubftituted  into  the  expreffion  for  the 
velocity,  we  fhall  have ~ for  the    velocity   when    the 

fri£tlon  ceafes. 

3.  \i  v-z=:a,  then  2s  no,  and  hence  the  body  will  continue  to 
move  uniformly  with  the  firft  velocity. 

4.  If  V  be  greater  than  a^  then  the  rotatory  motion  of  the 
point  a  on  the  plane  being  greater  than  its  progreflive  motion 
and  in  a  contrary  direction,  the  abfolute  motion  of  the  point 
a  upon  the  plane  will  be  in  the  direction  ML,  and  confequently 
fridtion  will  now  ad  in  the  diredion  LM  in  which  the  body 
moves,  and  therefore  will  accelerate  \.\\&  progrejjive  and  retard 
the  rotatory  motion ;  hence  it  appears,  that  the  progrejjive  mo-- 
ilon  of  a  body  may  b  accelerated  by  fribtion.  Now  to  deter- 
mine the  fpace  defcribed  before  the  motion  becomes  uniform,  we 
may  obferve,  that  as  the  progrellive  motion  of  the  body  is  now 
accelerated,  the  velocity  after  it  has  defcribed  any  fpace  %  will 
be  —s/a  4-  2F2;,  hence  the  velocity  acquired  =  s/a  +  z¥%  -  ^^  . 

and    confequently     the    rotatory     velocity    deflroyed     —    x 


■ '                       '                           y  (I         —     .        .  -  ■ 

^fl^-fzFz  — ^,      hence    v y^  s/a' -\-^^%- a  —  ^a' ■^■q.Yz.^ 


—a 


therefore  %  tz  — = ^ the  Ipace  required, 


,5;   if 


i8+  ^^^'  ViNCE  on  the  Motion  of 

5.  If  a  —  0,  or  the  body  be  placed  upon  the  plane  wichoiit 

any  progreffive  velocity,  then  z  —  ~~~ . 

Case  III.  i.  X.et  the  given  rotatory  motion  be  in  tlie  direc- 
tion ^^y';  then  as  the  friclion  muft  in  this  cafe  alv/ays  acl  in 
the  direction  ML,  it  miift  continually  tend  to  deftroy  both  the 
progreflive  and  rotatory  motion.  Now  as  the  velocity  de- 
flroyed  in  the  fame  time  is  in  proportion  to  the  retarding  force, 
and  the  force  which  retards  the  rotatory  is  to  the  force  which 
retards  the /(rijo-r^/i;^  velocity  by  Cor.  2.  Prop.  i.  as  r^:rj, 
therefore  if  1;  be  to  ^  as  ra  is  to  r  s^  then  the  retarding  forces 
being  in  proportion  to  the  velocities,  both  motions  will  be  de- 
flroyed  together,  and  confequently  the  body,  after  defcribing 
a  certain  fpace,  will  refl ;  which  fpace,  being  that  defcribed 
by  the  body  uniformly  retarded   by   the  force  F,  will,  from 

what  was  proved  in  Cafe  I.  be  equal  to  -r. . 

2.  If  V  bears  a  greater  proportion  to  a  than  ra  does  to  r s^ 
It  is  manifeft,  that  the  rotatory  motion  will  not  be  all  deftroyed 
when  the  progreflive  is  ;  confequently  the  body,  after  it  ha$ 

defcribed  the  fpace  -r,,  will  return  back  in  the  diredlion  ML; 

for  the  progreffive  motion  being  then  deftroyed,  and  the  rota- 
tory motion  ftili  continuing  in  the  dire<£tion  g  efy  will  caufc 
the  body  to  return  with  an  accelerative  velocity  until  the  fric- 
tion ceafes  by  the  body's  beginning  to  roll,  after  which  it  will 
move   on  uniformly.     Now  to  determine  the  fpace  defcribed 

before  this  happens,  we  have  r s  :  r  a  \\  a  \  ^-^ — -  the  rotatory 

Telocity  deftroyed   when    the  progreffive  is    all   loft ;    hencfi 

^  -  '[fiif  =  Vi!2zzl^llf  —  the  rotatory  velocity  at  that  time,  whiclaL 

being 


Bod:es  aff'ecJed  fy  Frisian,  185 

being   fubflltuted   for  v  in   the  lail:  article  of  Cafe  II.  gives 

i,^,s--ax^ta  ^^^  ^j^^  fpace  defcribed  before  the  motion  become? 

ahxai"  ^ 

uniform. 

3.  If  V  has  a  iefs  proportion  to  a  than  r  a  has  to  r  j,  it  is 
manifefl,  that  the  rotatory  motion  will  be  deftroyed  before  tiie 
frogrp[jive\  in  which  cafe  a  rotatory  motion  will  be  generated 
in  a  contrary  direction  until  the  two  motions  become  equal, 
when  the  fridion  will  inftantly  ceafe,  and  the  body  will  then 

move  on   uniformly.     Now  r a  \  r s  \\  v  '.  - — -  the  progreflive 

velocity   deftroyed  when   the    rotatory   velocity  ceafes,  hence 

a = ■ =  progreiiive  velocity  when  it  begins  its 

rotatory  motion   in   a  contrary  direction  ;  fubflitute  therefore 
this  quantity  for  a  m  the  expreffion  for  z  in  Cafe  L  and  we  have 


n^ -]-  2f'i  X  •  a  X  a  X  ra  —  V  X  r s 


iii~  X  ar 


i — r; —  for  the  fpace   defcribed   after  the   rota- 

tory  motion  ceafes  before  the  motion  of  the  body  becomes 
uniform.  Now  to  determine  the  fpace  defcribed  before  the 
rotatory  motion  was  all  deftroyed,  we  have  (as  the  fpace  from 
the  end  of  a  uniformly  retarded  motion  Varies  as  the  fquare  of 


a  axra  —  vxrs         aXra  —  vX  rs 


the  velocity)  a   :  —p  : : -^ :  — r^gr— -. —  the  fpace  that 

could  have  been    defcribed   from   the    time  that  the   rotatory 
velocity    was    deftroyed,  until   the  progrellive    motion    would 

Have  been  deflroyed  had  the  fri6lon  continued  to  acfl ;  hence 

._ ^4 

«  ax  ra  —  v  xrs         lav  X  raX  rs  —  v^  xri^         ■,        r  i    r     •  i      i       i 

re- HFU — 2 —  — v z =  the  Ipace  deicribed  when 

21'  '^r  X  ra  2.\  x  ra  ^ 

the  rotatory  motion  was  all  deftroyed,  hence 


.1 


rj*+  2' J  X  ra  X  a  X  a-  —  :  x  2av  Xra  Xrs  —  %?"  x  ri 


z^    ^^^L-  + i:^ ■■ -^'whoie  fpace    da- 

ai   xar   X2\:  2.b  x  ra  ^ 

fcribed  by  the  body  before  its  motion  becomes  uniform. 

Vol.  LXXV.  "  B  b  d  ->.- 


3?6  Mt\  ViNCE  on  the  Motion  of 

DEFINITION. 

'The  CENTER  of  FRICTION  IS  that  point  in  the  bafe  of  a  hoiy 

mi  which  it  revolves,  into  which  if  the  whole  furface  of  the  bafe^ 
mid  the  majs  of  the  body  were  collected^  and  made  to  revolve  about 
i'he  center  of  the  bafe  of  the  given  body,  the  angular  velocity  de- 
ft/oyed  by  its  fridiion  would  be  equal  to  the  angular  velocity  df/Iroyed-: 
in  the  given  body  by  itsfriBionin  the  fame  time. 

PROPOSITION      III. 

To  find  the  center  of  frldlion. 

Let  FGIi  (fig.  4.)  be  the  bafe  of  a  body  revolving  about  its 
center  C,  and   fuppofe  about    a,  b,  r,  &c.  to  be   indefinitely 
fmall  parts  of  the  bafe,  and  let  A,  B,  C,  &c.  be  the  correfpond- 
ing  parts  of  the  folid,  or  the  prifmatie  parts  having  a^  b,  c,  &c. 
for  their  bafes  ;  and  P  the  center  of  fri6lion.     Now  it  is  ma- 
nifeft,  that  the  decrement  of  the  angular  velocity  muft  vary 
as  the  whole  diminution  of  the  momentum  of  rotation  caufcd 
by  the  fri<£lion  dirc^ly,  and  as  the  whole  momentum  of  rota- 
tion or  efFe(£l  of  the  inertia  of  all  the  particles  of  the  folid  in- 
verfly  ;  X.\\Q  former  being  employed  in  diminifhing  the  angular 
velocity,  and  the  latter  in  oppofing  that  diminution  by  the  en- 
deavour of  the  particles  to  perfevere  in  their  motion.     Hence,- 
if  the  effe6l  of  the  friction  varies  as  the  effedl  of  the  inertia,, 
the  decrements  of  the  angular  velocity  in  a  given  time  will  be 
equal.     Now  as  the  quantity  of  fri6tion   (as  has  been  proved 
from  experiments)  does  not  depend  on  the  velocity,  the  efFedt 
of  the  fridion  of  the  elementary  parts  of  the  bafe  a,  b,  c,  &c. 
2  will 


iBodies  affedled  hy  FriSlloHk  187 

^Vlll  be  as  ^  X  rtC,  h  x  1>C,  c  x  cC,  &c.  alfo  the  efFc6t  of  the  Inertia 
of  the  correfponding  parts  of  the  body  will  be  as  A  x  aC\ 
B  X  ^C%  C  X  cC',  &c.  Now  when  the  whole  furface  of  the 
bafe  and  mafs  of  the  body  are  concentrated  in  P,  the  effecl:  of 
the  fri(5lion  will  be  as  ^  +  ^  4-  ^  +  &c.  x  CP,  and  of  the  inertia  as 
A  +  B  +  C  +  &c.  X  CP'" ;  confequently  a  x  aC  -{■  b  x  5C  -^r  c  x  cC 
+  &c.  :  T+T+TT &c.  X  CP  ::  Ax^C'"  +B  x  bC+CxcC^- 
+  &C.  :  A  +  B  4-  C  +  &c.  x  CP' ;  and  hence 

CP  =  --^  ■-- - - — — - —  ^       ^^—  ■—   (itS=:tneluni 

a  XaC -\-b  X  l^C  +  c X  cC  i- &:c.  X  A  +  ii  i-  C  -\-&.c. 

of  the  produces  of  each  particle  into  the  fquare  of  its  diftance 
from  the  axis  of  motion,  T:=::the  fiim  of  the  products  of  each 

part  of  the  bafe  into  its  diftance  from  the  center,  s  =  the  area 

s    J  ' 
of  the  bafe,  /  =  the  folid  content  of  the  body)  7^7—^. 

PROPOSITION     ly. 

Given  the  velocity  with  which  a  body  begins  to  revolve  ahotit  the- 
•center  of  its  bafe,  to  determine  the  number  of  revolutions  which  the 
body  will  make  before  all  its  motion  be  dejlroyed^ 

--  [U  hi 

■'Let  the  fridion,  expreffed  by  the  velbcityl.whieh'  it  Is  kbie  to' 
deftroy  in  th6' body  if  it  were  proiefted  in  a  right  line  hoi-i'zbn^ 
tally  in  one  fecolid,-  be  detefmirieid 'by' experiment,  dnd  cail^^F;' 
and  fappofe  th'e  initikl  velocity  *of' the- center  of  -fri^V-ion-  P  t about* 
^  to  be  a[  "Then  'conceiving  the  whole  fu-rfice  of  the  bafe-  ati^i 
m^fsT)f  "the  body  to 'be-  coUsfHed^ntS  the'^l5?iit  P,^  aft-d  §^s  -hks-^ 


B  b  7. 


1 88  Mr,yn;cTS.  on  the  Motion  of 

hence  if  we   put   z— PC,  /)  =  the    circumference   of   a  circle 
whole  radius  is  unity,  then  will  pz  =  circumference  defcribed 

by  the  point  P  ;  confequently  — ^=:  the  number  of  revolutions 

required. 

Cor.  It  the  folid  be  a  cyllnJer  and  r  be  the  radius  of  its  bafe, 

then  2,  =  —  ,  and  therefore  the  number  of  revolutions 


4      '  ""      X.W...WVX       V.X        .V..V.XV..XV...O-^^^p. 


PROPOSITION      V. 

91?  ^*f«£/  //6<?  nature  of  the  curve  defcribed  by  any  point  of  a  body 
qfcdUd  by  friBion,  when  it  defends  down  any  inclined  plane. 

Let  efg  (fig.  5.)  be  the  body,  the  points  ^,  r,  j,  as  in  Prop.  L 
and  conceive  j  /,  r  ;/,  to  be  two  indefinitely  fmall  fpaces  defcribed 
by  the  points  s  and  r  in  the  fame  time,  and  which  therefore 
will  reprelent  the  velocities  of  thofe  points ;  but  from  Prop.  I. 
the  ratio  of  thefe  velocities  is  cxprefled  by  m  x  CB  :  a  x  CA, 
hence  s  t  :  r  n  i:  m  x  CB  :  a  x  CA.  With  the  center  r  let  a 
circle  1;  w  be  defcribed  touching  the  plane  LM  which  is  parallel 
to  AC  at  the  point  b,  and  let  the  radius  of  this  circle  be  fuch. 
that,  conceiving  it  to  defcend  upon  the  plane  LM  along  with 
the  body  defcending  on  CA,  the  point  b  may  be  at  reft,  or  the 
circle  may  roll  without  Aiding.  To  determine  which  radius^ 
produce  r  s  to  ;v,  parallel  to  which  draw  n  dy,  and  produce  n  t 
to  %  ;  now  it  is  manifeft,  that  in  order  to  anfwer  the  conditions 
;4bove-mentioned,  the  velocity  of  the  point  x  mufl  be  to  the 
velocity  of  the  point  r  as  2;  :.i,.  that  is,  %x  :  y  x  ::  2  :  1^ 
hence   zyz:zyx  =  nr.      Now    zy  :  dt  {\:  ny  :  nd)  n  rx  i  r si 

therefore  ^/=:— x%y=:— x  «r,  hence ^j  (=:td+ds  =  fd-^nrzz 
4  ^^ 


ridlrt.  Trruu^  I',,!.  /.A:\TT,i:.,\'I[/..  /iS. 


BoMes  rfff5fcd  by  FridfJon.  iSp 

-i  X  «r  +  /;Or='^^i^X«/',   confequently  "^"^ — ^;  i  ::   is  '.  nr  :: 

(from    what  is    proved     above)    /«xCB:^7xCA;     therefore 
a  X  CA  X  r s  +  a  x  CA  x  r.v  =  f;2  x  CB  x  r  x^  hence  r  v  =» 

..^^  "  ^^{      the    radius   of    the    circle    which    roUina;  down 
mxCH— ^xCa  ^ 

the  inclined  plane  LM,  and  carrying  the  hody  with  it,  will 
give  the  true  ratio  of  its  progreliive  to  its  rotatory  motion, 
and  confequently  that  point  of  the  circle  which  coincides  with 
any  given  point  of  the  body  will,  as  the  circle  revolves  upon 
the  line  LM,  defcribe  the  fame  curve  as  the  correfponding 
point  of  the  body  ;  but  as  the  nature  of  the  curve  defcribed  by 
any  point  of  a  circle  revolving  upon  a  flraight  line  is  already 
very  well  known,  it  feems  unnecelTary  to  give  the  invefligation. 
By  a  method  of  reafoning,  not  very  different,  may  the  nature 
of  the  curve,  which  is  defcribed  by  any  point  of  a  body  moving 
"Upon  an  horizontal  plane,  and  affected  by  fridtion,  be  determined. 


[     '9°    ] 


XI.  Ohjervatlo?2s  and  Experiments  on  the  Light  of  Bodies  In  a 
State  of  Combujlion,  By  the  Rev.  Mr.  Morgan  ;  comviiinicated 
by  the  Rev.  Richard  Price,  LL.D.  F.R.S. 


Read  January  27,   1785.  -        - 

THE  difcuflion  which  I  now  wifh  to  lay  before  the  Royal 
Society  is  nothing  more  than  a  feries  of  facfls,  and  of 
conclafions  which  feem  to  flow  from  thofe  fadls,  and  from  an 
attention  to  the  following  data. 

I.  That  light  is  a  body,  and  like  all  other  bodies  fubjedl  to 
the  laws  of  attraction. 

II.  That  light  is  an  heterogeneous  body,  and  that  the  fame 
attractive  power  operates  with  different  degrees  of  force  on  its 
different  parts. 

III.  That  the  light  which  efcapes  from  combuftibles  when 
decompofed  by  heat,  or  by  any  other  means,  was,  previous  to 
its  efcape,  a  component  part  of  thofe  fubflances. 

It  is  an  obvious  conclufion  from  thefe  data,  that  when 
the  attra«£live  force,  by  which  the  feveral  rays  of  light 
are  attached  to  a  body,  is  weakened,  fome  of  thofe  rays  will 

efcape 


Mr.  Morgan's  Obfervdtions  and Experhnents,  &c.       lot 
efcape  fooner  than  others.  Thofe  which  are  united  with  theleafl 
degree  of  power  will   efcape  firll,  and  thofe  which  adhere  to  it 
mod  ftrongly  will  (if  I  may  be  allowed  the  expre(hon)  be  the 
lall:  to  quit  their  bafis.     We  may  here  have  recourfe  to  a  flimiliar 
fa6l,    which     is    analogous   to    this,     and    will    illuflrate    it. 
If  a    mixture,  confifting    of  equal    parts   of   water,  of  fpirits 
of    wine,    and  of  other  more   fixed    bodies,    be    placed    over 
a  fire ;  the  firft  influence  of  that  heat,   to   which  all  the  in- 
gredients   ar€    alike    expofed,    will    carry    off    the    fpirits    of 
wine   only.       The    next  will   carry   off   the   fpirits   of    wine 
blended   with  particles   of  water.      A  flill  greater   degree  of 
heat    will  blend  with    the    vapour  which    efcapes    a    part    of 
the  more  fixed   bodies,  till  at  length  what  evaporates  will  be  a 
mixture  of  all   the  ingredients  which   were  at  firft  expofed  to 
the  fire.     In  like  manner,  when  the  furface  of  a  combuflible  is 
in  aflate  of  decompofition,  thofe  parts  which  are  the  leafl  fixed, 
or  which  are  united  to  it  with  the  leafl  force,   will  be  feparated 
firfl.     Amongft  thefe  the  indigo  rays  of  light  will  make  the 
earliefl:  appearance.     By  increafing  the  heat  we  fhall  mix  the 
violet  with  the  indigo.     By  increafing  it  flill  more  we  fhall  add 
the  blue  and  the  green  to  the  mixture,  till  at  length  we  reach 
that  intenfity  of  heat  which  will  caufe  all  the  rays  to  efcape 
at   the    fame  inflant,  and  make  the   flame   of  a    combuflible 
perfedlly   white.     It   is  not  my  pre  fen  t    defign    to  fhew  why 
the  mofl   refrangible  rays  are  the   firfl  which   efcape   from  a 
burning  body,  but  to  enumerate  the  feveral  fads  which  feem  to 
fhew,  that  fuch  a  general  law  takes  place  in  combuftion  ;  and 
that  the  various   colours  of  bodies  in   this  flate  are  uniformly 
regulated  by  that  decreafe  of  attradive  force  now  defcribed. 

By 


i(^z       My.  Morgan's  Ohfa'vallons  and Expdr'unents  on 

By  examining  the  flame  of  a  common  candle  we  may  ob- 
fervc,  that  its  iowefl  extremities,  or  the  part  in  which  the  black 
colour  of  the  wick  terminates,  dilcharges  the  lead  heat;  and 
that,  as  the  vertex  of  the  flame  is  approached,  a  fucceffive  order 
ot  parts  is  paflld  through,  in  whicii  the  loweft  is  continually 
adding  to  the  heat  of  what  is  juft  above  it,  till  w^e  come  to 
the  top  of  the  flame,  near  which  all  the  heat  is  collecled  into  a 
focus.  i\t  the  loweil  extremity,  however,  where  the  heat  is 
inconfiderable,  a  blue  colour  may  be  always  obferved ;  and 
from  this  appearance,  amongfi  others,  it  may,  I  think,  be 
fafely  concluded,  that  the  blue  rays  are  fome  of  thofe  which 
efcape  from  combuflibles  in  an  early  period  of  their  decompo- 
fition  ;  and  that  if  the  decompofition  could  be  examined  in  a 
period  flill  more  early,  the  colour  of  their  flame  would  be 
violet.  By  an  a  priori  deduction  of  this  kind,  I  was  led  to 
watch  the  appearances  of  a  candle  more  attentively  ;  whence  I 
found  that  to  the  external  boundary  of  a  common  candle 
is  annexed  a  filament  of  light,  which,  if  proper  care  be 
taken  to  prevent  the  efcape  of  too  much  fmoke,  will  appear 
moft  beautifully  coloured  with  the  violet  and  indigo  rays.  To 
the  preceding  inftance  of  a  common  candle  many  fa£ls  may 
be  added,  which  fpeak  a  fimilar  language.  If  fulphur  or 
asther  is  burned,  or  any  of  thofe  combuflibles  whofe 
vapour  is  kindled  in  a  fmall  degree  of  heat,  a  blue  flame 
will  appear,  which,  if  examined  by  the  prifm,  will  be  found 
to  confrft  of  the  violet,  the  indigo,  the  blue,  and  fometimes  a 
fmall  quantity  of  the  green  rays.  The  beft  mode,  however, 
of  (hewing  the  efcape  of  fome  rays  by  that  degree  of  heat 
which  will  not  feparate  others  till  increafed,  is  the  following. 
Give  a  piece  of  brown  paper  a  fpherical   form,  by  prefling  it 

upon 


■the  Ll^ht  of  Bodies  in  a  State  of  Comhufic-tu  1 93 

npon  any  hard  globular  fubftance,  Gradually  bring  the  paper, 
thus  formed,  to  that  diftance  from  the  candle  at  which  it  will  be- 
gin to  take  fire.  In  this  cafe  a  beautiful  blue  flame  may  be  feen, 
hanging  as  it  were  by  the  paper  till  a  hole  is  made  in  it,  when 
the  flame,  owing  to  the  increafed  a6lion  of  the  air  upon  all. 
parts  of  it,  becomes  white,  though  the  edges  ftill  continue  of 
a  blue  or  violet  colour.  As  a  confirmation  of  what  I  have 
concluded  from  the  preceding  fa£ls,  it  may  be  obferved,  that 
the  very  flame  which,  when  expofed  to  a  certain  degree  of 
heat,  emitted  the  mofl  refrangible  rays  only,  will,  if  expofed 
to  a  greater  degree  of  heat,  emit  fuch  as  are  lefs  refrangible* 
The  flames  of  fulphur,  fpirits  of  wine,  &c.  when  fuddenly 
expofed  to  the  heat  of  a  reverberatory,  change  their  blue  ap- 
pearance for  that  .which  is  perfe6lly  white.  But  to  gain  a 
more  flriking  diverfity  of  this  faft,  I  adopted  Mr.  Melvill*s 
mode  of  examining  bodies  whilfl:  on  fire.  I  darkened  my 
room,  and  placed  between  my  eye  and  the  combuftible  a  (lieet 
of  pafteboard,  in  the  center  of  which  I  made  a  fmall  perfora- 
tion. As  the  light  of  the  burning  body  efcaped  through  this 
perforation,  I  examined  it  with  a  prifm,  and  obferved  the  fol- 
lowing appearances.  When  the  fpirits  of  wine  were  fet  on 
fire,  all  the  rays  appeared  in  the  perforation ;  but  the  violet, 
the  blue,  and  the  green,  in  the  greatefl  abundance.  When 
the  combuflion  of  the  fpirits  was  checked  by  throwing  fome 
fal  ammoniac  into  the  mixture,  the  red  rays  difappeared ;  but 
when,  by  the  long  continuance  of  the  flame,  the  'fal  ammoniac 
was  rendered  fo  hot  as  to  increafe,  rather  than  diralnifh  thci 
combuflion,  the  red  rays  again  appeared  at  the  perforation.  If 
the  fcreen  was  managed  fo  that  the  different  parts  of  the 
fiame  might  be  examined  feparately,  I  always  obferved  that 
Vol.  LXXV.  C  c  -  the 


3  94  ^^^'  Morgah's  Ohfe^vaitons  and  Expenmenis  on 
the  colours  varied  according  to  the  degree  of  heat.  At 
the  bafe  of  the  flame,  or  where  the  heat  was  leaft,  the  in- 
digo, the  violet,  and  a  very  fmall  tinge  of  the  bkie  and 
green  appeared.  As  I  approached  the  vertex  of  the  flame, 
the  rays  which  efcaped  became  mors  and  more  numerous 
till.  I  reached  the  top,  when  all  the  rays  appeared  in  the 
prilra.  It  fhould  be  attended  to,  that  when  the  red  rays  firft 
made  their  appearance,  their  quantity  was  fmall,  and  gradually 
increafed  as  the  eye  in  its  examination  approached  that  part 
where  the  heat  was  greatefl:.  Mr.  Melvill,  w^hen  he  made 
fome  of  the  preceding  experiments,  obferved,  that  the  yellow 
rays  frequently  efcaped  in  the  greateft  abundance ;  but  this  fin> 
gularity  proceeded  from  fome  circumftanccs  which  efcaped  his 
attention.  In  confequence  of  mixing  acids  or  falts  with  the 
burning  fpirits,  a  very  denfe  fume  of  unignited  particles  arifes^ 
and  before  the  rays  of  the  burning  body  arrive  at  the  perfora- 
tion where  the  prifra  catches  them,  they  muft  pafs  through  a 
medium  which  will  abforb  a  great  part  of  the  indigo  and  the 
violet.  On  the  other  hand,  owing  to  the  imperfection  of  tjie 
decompofition,  very  few  of  the  red  rays  are  feparated  from  their 
bafis,  and  confequently  the  yellow  and  the  orange  rays  are 
thofe  alone  which  pafs  through  the  unburn t  fmoke  of  the 
flame. 

1  would  now  proceed  with  obferving,  that,  befides  the  in- 
creafe  or  decreafe  of  heat,  there  are  other  modes  of  retarding 
or  accelerating  the  combuftion  of  bodies,  by  which  alfo  may 
be  examined  fome  of  the  preceding  illuftrations. 

I.  A  candle  burns  moft  rapidly  and  brilliantly  in  dephlo- 
g^ifticated  air. 

z»  The 


the  Light  of  Bodies  in  a  State  of  Combujlion,  j  9 ; 

2.  The  blue  colour  of  a  fulphurcous  flame  in  pure  air  is 
•changed  into  a  dazzling  white. 

3.  The  flame  of  inflammable  air,  when  mixed  with  ni- 
trous air,  is  green.  It  is  white  flrongly  tinged  wjth  the  indigo 
and  violet  when  mixed  with  common  air ;  but  when  mixed 
with  dephlogifticated  air,  or  furrounded  by  it,  the  brilliancy 
of  its  flame  is  moft  Angularly  beautiful. 

If  the  preceding  fa^ls  prove  that  light,  as  an  heterogeneous 
body,  is  gradually  decompofed  during  combuftion ;  if  they 
prove,  likewife,  that  the  indigo  rays  efcape  with  the  leaf!:  hear, 
and  the  red  with  the  greateft ;  I  think  we  may  rationally  ac- 
count for  feveral  Angularities  in  the  colours  of  different  flames. 
If  a  piece  of  paper,  impregnated  with  a  folution  of  copper  in 
the  nitrous  acid,  be  fet  on  fire,  the  bottom  and  fides  of  the 
flame  are  always  tinged  with  green.  Now  this  flame  is  evi- 
dently in  that  weak  flate  of  decompofition,  in  which  the  mofl 
refrangible  rays  efcape  in  the  greatefl  abundance ;  but  of  thefe 
rays  the  green  efcape  moil  plentifully  through  the  unignited 
vapour  and  that  portion  of  the  atmofphere  which  feparates  the 
eye  from  the  flame.  The  peculiarity  which  I  have  now  endea- 
voured to  account  for  may  be  obferved  in  the  greatefl  perfection 
in  brafs  founderies.  The  heat  in  this  inflance,  though  very 
ftrong,  is  fcarcely  adequate  to  the  decompofition  of  the  metallic 
vapour  which  efcapes  from  the  melted  brafs.  A  very  Angular 
flame  therefore  appears  to  the  eye ;  for  while  its  edges  are  green, 
its  body  is  fuch  as  to  give  the  objeds  around  a  very  pallid  or 
ghaflily  appearance,  which  is  the  confequence  of  its  wanting 
that  portion  of  red  rays  which  is  neceflary  to  make  a  perfed 
white* 

C  c  a  The 


i(j6        Mr.  Morgan's  Ohfervatlom  and  Experiments  ort 

The  moH  fingular  phenomenon  attending  a  burning  body 
iS,  perhaps,  the  red  appearance  it  aflumes  in  its  lafl:  ftage  of 
coiribiiiLlon.  The  preceding  fatls  and  obiervations  may,  I 
think,  help  us  to  explain  it. 

1.  After  a  body  has  continued  to  burn  for  fome  time,  its 
external  lurface  is  to  be  regarded  as  having  loft  a  great  portion 
if  not  the  whole  of  thofe  rays  which  the  firfl  application  of 
heat  was  able  to  feparat'e.  Bat  thefe  rays  w^ere  the  indigo,  the 
violet,  the  blue,  and  perhaps  the  green.  Nothing,  therefore,  will 
remain  to  be  fepa rated,  buttbe  yellow,  the  orange,  and  the  red, 
C^onfequently,  the  combuftion  of  the  body,  in  its  lafl:  ftate  of  de- 
compolition,  can  afllime  no  other  than  a  reddifli  appearance.  But 

2.  Let  us  con-fide  r  the  external  fur  face  of  the  combuflible 
as  annexed,  to  an  inner  furfaee,  which  may  be  partly,  but  not  fo 
perfectly  decompoled  as  itfelf :  for  the  violence  of  the  heat  will 
be  found  to  lelien  in  its  effeds  the  nearer  it  approaches  to  the 
center  of  the  fubftance  which  is  expofed  to  it.  Hence  we  are 
to  confider  the  parts  which  are  juft  covered  by  the  external  fur- 
face  as  having  loft  lefs  of  their  component  light  than  the  exter- 
nal furfaee  itfelf.  Or  the  former  may  retain  the  green  rays 
when  the  latter  has  loft  both  indigo,  violet,  blue,  and  green. 

3.  Thofe  parts  which  are  nearer  the  center  of  the  body 
than  either  of  the  preceding  muft,  as  they  are  further  from 
the  greateft  violence  of  the  heat,  have  loft  proportionably 
fewer  of  tlieir  rays.  Or  w^hile  the  more  external  parts  may 
have  loft  all  but  the  red,  thefe  may  have  loft  only  the  indigo 
snd  viokt. 

4»  The  moil  central  parts  may  be  unafFeded  by  the  heat ; 
and  whenever  the  fire  does  reach  thefe  parts,  they  will  imme- 
diately difcharge  their  indigo  rays,  and  be  decompofed  in  the 

gradual 


the  Light  cj  bodies  in  a  State  of  Combufiion,  197 

gradual  manner  which  I  have  already  defcribed.  A  piece  of 
rotten  wood,  whilil:  burning,  will  exemplity  and  confirm  the 
preceding  illuftration.  When  influenced  by  the  external  air 
only,  if  examined  through  a  prifm,  no  rays  will  be  found  to 
efcape  but  the  orange  and  the  red.  By  blowing  upon  the 
burning  wood  with  a  pair  of  bellows,  the  com  bullion, 
being;  increafed,  will  affect  thofe  internal  parts  of  the  body 
which  were  not  adled  upon  before.  Thefe  parts,  therefore, 
will  begin  to  lofe  their  light,  and  a  prifm  will  {hew  the 
green,  the  blue,  the  violet,  and  indlgOy  all  appearing  in  fuc- 
ceffion*  Appearances  hmilar  to  the  preceding  may  be  ob- 
ferved  in  a  common  kitchen  fire.  When  it  is  fainted:,  its 
colour  is  moll:  red,  the  other  rays  having  been  emitted,  and 
the  combuftion  at  a  fland  ;  but  by  blowing  upon  it  in  this 
ftate,  its  brightnefs  will  be  increafed,  and  more  and  more  of 
the  rays  which  are  yielded  by  the  internal  parts  of  the  body 
will  come  to  the  eye,  till  at  length,  by  continuing  to  blow,  the 
combufiion  will  be  made  fo  complete  as  to  yield  all  the  rays, 
or  to  make  it  appear  perfectly  white. 

Many  are  the  varieties  difcoverable  in  the  flanies  and  In  the 
appearances  of  fixed  burning  bodies  to  which  the  preceding 
obfervations  may  be  applied  ;  but,  to  avoid  unnecefl'ary  amplifi- 
cation I  will  take  notice  only  of  what  appears  to  me  an  imper- 
fedion  in  Sir  Isaac  Newton's  definition  of  flams.  He  con- 
je6i:ures,  that  it  may  be  a  vapour  heated  red-hot.  I  think  I 
fliould  rather  fliy,  that  flame  Is  an  inflance  of  combufiion 
whofe  colour  will  be  determined  by  the  degree  of  decon.ipofi- 
tloii  which  takes  place.  If  it  be  very  imperfe^l,  the  molf 
refrangible  rays  only  will  appear.  If  it  be  very  perfe<5l,  all 
the  rays   will   appear,    and    its     flame    will    be   brilliant    in 

proportiof\ 


193  Mr.  Mob. can's  Ohfervations  and  Experiments  on 
proportion  to  this  perfe£tion.  There  are  flames,  however, 
which  confift  of  burning  particles,  whole  rays  have  partly 
efcaped  before  they  afcended  in  the  form  of  vapour.  Such 
would  be  the  flame  of  a  red-hot  coal,  if  expofed  to  fuch  a  heat 
as  would  gradually  difperfe  it  into  vapour.  When  the  fire  is 
very  low  under  the  furnace  of  an  iron  foundery,  at  the  upper 
orifice  of  the  chimney  a  red  flame  of  this  kind  may  be  feen, 
which  is  different  from  the  flame  that  appears  immediately  after 
frefh  coals  have  been  thrown  upon  the  fire ;  for,  in  confe- 
quence  of  adding  fuch  a  fupply  to  the  burning  fuel,  a  vafi: 
column  of  fmoke  afcends,  and  forms  a  medium  fo  thick  as  to 
abforb  mofl  of  the  rays  excepting  the  red, 

"Experiments  on  eleSiric  light. 

If  we  would  wifh  to  procure  any  degree  of  certainty  in  any 
hypothefis  which  we  may  form  concerning  ele£lrical  light, 
perhaps  the  following  general  dedu£lions  may  be  of  fome  fer* 
vice  to  us. 

1.  There  is  no  fluid  or  folid  body  in  its  pafTagc  through 
W'hich  the  eledlric  fluid  may  not  be  made  luminous.  In  water, 
fpirits,  oil,  animal  fluids  of  all  kinds,  the  difcharge  of  a  Ley- 
den  phial  of  almofl  any  fize  will  appear  very  fplendid,  pro- 
vided we  take  care  to  place  them  in  the  circuit,  fo  that  the 
fluid  may  not  pafs  through  too  great  a  quantity  of  them.  My 
general  method  is  to  place  the  fluid,  on  which  I  mean  to  make 
the  experiment,  in  a  tube  three-quarters  of  an  inch  in  diameter, 
and  four  inches  long.  I  flop  up  the  orifices  of  the  tube  with 
two  corks,  through  which  I  pufh  two  pointed  wires,  fo  that  the 
points  may  approach  within  one-eighth  of  an  inch  to  each 
2  other. 


the  Light  of  Bodies  in  a  State  of  Comhiflion,  199 

other.  The  fluid  in  palling  through  the  interval  which  fepa- 
rates  the  wires  is  always  luminous,  if  a  force  be  ufed  fufii- 
ciently  flrong.  1  fhould  obferve,  that  the  glafs  tube,  if  not 
very  thick,  always  breaks  when  this  experiment  fucceeds.  To 
make  the  paflage  of  the  fluid  luminous  in  the  acids,  they  muft 
be  placed  in  capillary  tubes,  and  two  wires  introduced,  as  in 
the  preceding  experiment,  whofe  points  (hall  be  very  near  each. 
other.  It  is  a  well  known  fa6t,  that  the  difcharge  of  a  fmall 
Leyden  phial  in  pafling  over  a  flrip  of  gold,  lilver,  or  Dutch 
^letal  leaf,  will  appear  very  luminous.  By  conveying  the  con- 
tents of  ajar,  mcafurlng two  gallons,  over  a  ftrip  of  gold  leaf 
one-eighth  of  an  inch  in  diameter,  and  a  yard  long,  I  have 
frequently  given  the  whole  a  dazzling  brightnefs.  I  cannot 
fay,  that  a  much  greater  length  might  not  have  been  made 
very  fplendid,  nor  can  I  determine  to  what  length  the 
force  of  a  battery  might  be  made  luminous  in  this  manner. 
We  may  give  this  experiment  a  curious  diverfity,  by  laying 
the  gold  or  filver  leaf  on  a  piece  of  glafs,  and  then  placing  the 
glafs  in  water ;  for  the  whole  gold  leaf  will  appear  molf  bril- 
liantly luminous  in  the  water  by  expofing  it,  thus  circum- 
flanced,  to  the  explofion  of  a  battery. 

2,  The  difficulty  of  making  any  quantity  of  the  eledlrical 
fluid  luminous  in  any  body  increafes  as  the  condudling  power 
of  that  body  increafes. 

EXP.  I.  In  order  to  make  the  contents  of  a  jar  luminous 
in  boiling  water,  a  much  higher  charge  is  neceffary  than  would, 
be  fufficlent  to  make  it  luminous  in  coLd  water,  which  is  uni- 
verfally  allowed  to  be  the  worft  conduftor. 

EXP.  II.  I  have  various  reafons  for  believing  the  acids  to 
be  very  good  conductors.  If  therefore  into  a  tube,  filled  with 
"Water,  and  circumftanced  as  I  have  already  defcribed,  a   few 

drops 


200       Mr,  Morgan's  Obfervaiions  cmd  Experiments  on 

drops  of  either  of  the  mineral  acids  are  poured,  it  will  be 
almoft  impoffible  to  make  the  fluid  luminous  in  its  paflage 
through  the  tube. 

EXP.  III.  If  a  jflring*,  whofe  diameter  is  one-eighth  of  an 
inch  and  whofe  length  is  fix  or  eight  inches,  is  moiftened  with 
water,  the  contents  of  a  jar  will  pafs  through  it  luminoufly, 
but  no  fuch  appearance  can  be  produced  by  any  charge  of  the 
fame  jar,  provided  the  fame  firing  be  moiftened  with  one  of 
the  mineral  acids.  To  the  preceding  inftance  we  may  add 
the  various  inftances  of  metals  which  will  conduct  the  eledtri-' 
cal  fluid  without  any  appearance  of  light,  in  circumftances 
the  fame  with  thofe  in  which  the  fame  force  would  have  ap- 
peared luminous  in  pafling  through  other  bodies  whofe  con- 
ducting power  is  lefs.     But  I  proceed  to  obferve, 

III.  That  the  eafe  with  which  the  eledrical  fluid  is  rendered 
luminous  in  any  particular  body  is  increaled  by  increafing 
tiie  rarity  of  the  body.  The  appearance  of  a  fpark,  or  of 
the  difcharge  of  a  Leyden  phial,  in  rarefied  air  is  well  known. 
But  we  need  not  reft  the  truth  of  the  preceding  obfervation  on 
the  feveral  varieties  of  this  fa6t ;  fimilar  phenomena  attend  the 
rarefaction  of  aether,  of  fplrits  of  wine,  and  of  water. 

EXP.  IV.  Intothe  orifice  of  a  tube,  48  inches  long,  and  two- 
thirds  of  an  inch  in  diameter,  I  cemented  an  iron  ball,  fo  as  to 
bear  the  weight  which  prefled  upon  it  when  I  filled  the  tube 
with  quickfilver,  leaving  only  an  interval  at  the  open  end, 
which  contained  a  few  drops  of  water.  Having  inverted  the 
tube,  and  plunged  the  open  end  of  it  into  a  bafon  of  mercury, 
the  mercury  in  the  tube  flood  nearly  half  an  inch  lower  than  it 

*  The  thicknefs  and  diameter  of  the  ftring  fliould  be  regulated  by  the  force  we 
employ, 

did 


f 

the  hight  of  Badics  ?/?  a  Siate  of  Cornkfrju^  z-^t 

did  In  a  barometer  at  the  fltme  inftant,  owing  to  the  Yapour 
which  was  formed  by  the  water.  But  through  this  rarefied  wa- 
ter the  ele£lrical  fpark  palled  as  luiniiioudy  as  ii;  does  through 
air  equally  rarefied. 

EXP.  V.  If,  inflead  of  water,  a  few  drops  of  fpirits  of  wine  ari 
placed  on  the  furface  of  the  mercury,  phi^enomena  fimilar  to 
thofe  of  the  preceding  experiment  will  be  difcovered,  with 
this  difference  only,  that  as  the  vapour  in  this  cafe  is  more 
denfe,  the  ele6lrical  fpark  in  its  paffage  through  it  is  not  q^uite 
fo  luminous  as  it  is  in  the  vapour  of  water. 

EXP.  VI.  Good  aether  fubftituted  in  the  room  of  the  fpirits 
of  wine  will  prefs  the  mercury  down  fo  low  as  the  height  of 
1 6  or  17  inches.  The  eledrical  fluid  in  pafling  through  this 
vapour  (unlefs  the  force  be  very  great  indeed)  is  fcarcely  lumi- 
,nous.  But  if  the  preffure  on  the  furface  of  the  mercury  in  the 
bafon  be  gradually  leflened  by  the  aid  of  an  air-pump,  the  va- 
pour will  become  more  and  more  rare,  and  the  eledric  fpark  in 
pafling  through  it  more  and  more  luminous. 

EXP.  vii.  I  could  not  difcover  that  any  vapour  efcaped  from 
the  mineral  acids  when  expofed  in  vacuo,  To  give  them, 
therefore,  greater  rarity  or  tenuity,  I  found  different  methods 
neceflary.  With  a  fine  camel-hair  pencil,  dipped  in  the  vi- 
triolic, the  nitrous,  or  the  marine  acid,  I  drew  upon  a  piece  of 
glafs  a  line  about  one-eighth  of  an  inch  broad.  In  fome  in- 
ftances  I  extended  this  line  to  the  length  of  27  inches,  and 
found  that  the  contents  of  an  elecShric  battery,  confifliing  of  la 
pint  phials  coated,  would  pafs  over  the  whole  length  of  this 
line  with  the  greatefl  brilliancy.  If  by  widening  the  line,  or 
by  laying  on  a  drop  of  the  acid,  its  quantity  was  increafed 
in  any  particular  part,  the  charge,  in  paffing  through  that  part, 
never  appeared  luminous.  Water,  fpirits  of  wine,  circum- 
Vol.  LXXV.  D  d  flanced 


202  Mr.  Morgan's  Ohjeivailons  and  Experiments  on 
flauced  fimilai'ly  to  the  acids  in  the  preceding  experiment, 
were  attended  with  iiiiiilar,  hut  not  equal  effects,  hecaule,  in 
confequence  of  the  inferiority  of  their  condu6ling  power,  it  was 
necefiary  to  naake  the  line  through  which  the  charge  palled 
confiderably  fliorter. 

4.  The  brilliancy  or  fplendor  of  the  ele^lric  fluid  in  its 
pafiage  through  any  body  is  always  increafed  by  leilenlng  the 
dimeniions  of  that  body.  I  would  explain  my  meaning  by  fay- 
ing, that  a  fpark,  or  the  difcharge  of  a  battery  which  we  might 
fuppofe  equal  to  a  fphere  one  quarter  of  an  inch  in  diameter, 
would  appear  much  more  brilliant  if  the  fame  quantity  of  fluid 
is  compreffcd  into  a  fphere  one-eighth  of  an  inch  in  diameter.. 
Thisobfervation  is  the  obvious  ccnfequenceof  many  known  facls. 
If  the  machine  be  large  enough  to  afford  a  fpark  whofe  length 
is  nine  or  ten  inches,  this  fpark  may  be  {tzw  fometlmes  forming 
itfelf  into  a  brufli,  in  which  flate  it  occupies  more  room,  but  ap- 
pears very  faintly  luminous.  At  other  times  the  fame  fpark  may 
be  feen  dividing  itfelf  into  a  variety  of  rr.mifications  which  fhoot 
into  the  furnmndliig  air.  In  this  cafe,  likewlfe,  the  fluid  is 
diffufed  over  a  large  luiface,  and  in  proportion  to  the  extent  of 
that  furface,  fo  is  the  faintnefs  of  the  appearance.  A  fpark, 
which  in  the  open  air  cannot  exceed  one  quarter  of  an  inch  in 
diameter,  will  appear  to  fill  the  whole  of  an  exhaufted  receiver 
four  inches  Vv'lde  and  eight  inches  long.  But  in  the  former 
cafe  it  is  brilliant,  and  in  the  latter  it  grows  fainter  and  fainter 
as  the  (ize  of  the  receiver  increafes.  To  prove  the  obfervation, 
which  I  think  m.ay  be  juftined  by  the  preceding  fads,  I  made 
the  following  experim.ents. 

EXP.  VIII.  To  an   Infulated   ball,   four  inches  in  diameter,  I 

fixed   a  filver  thread,   about  four  yards  long.     This  thread,   at 

the  end  which  was  remotefl  from  the  ball,  was  fixed  to  another 

^  infulated 


the  Light  of  Bodies  in  a  State  of  Comhujlion,  203 

infulated  fubftance.  I  brought  the  ball  withui  the  ftrlking 
diftance  of  my  condu^lor,  and  the  fpark  in  pading  from  the  cou- 
du^lorto  the  ball  appeared  v^ery  brilliant ;  but  the  whole  length 
of  the  filver  thread  appeared  faintly  luminous  at  the  fame  in- 
ilant.  In  other  words,  when  the  fpark  was  confined  within 
the  dimenfions  of  a  fphere  one-eighth  of  an  inch  in  diameter, 
it  was  bright,  but,  when  difriifed  over  the  furface  of  c^ir  which 
received  it  from  the  thread,  its  light  became  fo  faint  as  to  be 
{&t\\  only  in  a  dark  room.  If  I  leflened  the  furface  of  air 
which  received  the  fpark  by  ihortening  the  thread,  I  never 
failed  to  increafe  the  brightnefs  of  the  appearance. 

EXP.  IX.  To  prove  that  the  faintnefs  of  the  eledtric  light  in 
'vacuo  depends  on  the  enlarged  dimeniions  of  the  fpace  through 
which  it  is  difFufed,  we  have  nothing  more  to  do  than  to  in- 
troduce two  pointed  wires  into  the  vacuum,  fo  that  the  fluid 
may  pafs  from  the  point  of  the  one  to  the  point  of  the  other, 
when  the  diftance  between  them  is  not  more  than  the  one-tenth 
of  an  inch.  In  this  cafe  we  ihali  find  a  brilliancy  as  great  as 
in  the  open  air. 

EXP.  X.  Into  a  Torricellian  vacuum,  36  inches  in  length,  I 
conveyed  as  much  air  as  would  have  filled  two  inches  only  of  the 
exhaufted  tube,  if  it  were  inverted  in  water.  This  quantity  of 
air  afforded  refiftance  enough  to  condenfe  the  fluid  as  it  pafled 
through  the  tube  into  a  fpark  38  inches  in  length.  The  bril- 
liancy of  the  fpark  in  condenfed  air,  in  water,  and  in  all  fub- 
flances  through  which  it  paiTes  with  difficulty,  depends  on 
principles  iimilar  to  thofe  which  account  for  the  preceding  fa(^s. 
I  would  now  proceed  to  fhew, 

5.  That  in  the  appearances  of  ele£lriclty,  as  well  as  in  thofe 
of  burning  bodies,  there  are  cafes  in  which  all  the  rays  of  light 
do  not  efcape ;  and  that  the  mofl  refrangible  rays  are  thofe 

D  d  2  which 


2^4        Mr.  MoRGAN^s  Obfervat'wtu  and  Experiments  on 

which  efcape  firft  or  moft  eafily.  The  ele£lrical  brufli  Is 
always  of  a  purple  or  bluiOi  hue.  If  you  convey  a  fpark 
through  a  Torricellian  vacuum,  made  *  withGiit  boiling  the 
mercury  in  the  tube,  the  brufh  will  difplay  the  indigo  ra\^s. 
The  fpark,  however,  may  be  divided  and  weakened  even  in 
the  open  air,  fo  as  to  yield  the  moil  refrangible  rays  only. 

EXP.  XI.  To  an  infulated  metallic  ball,  four  inches  in  dia- 
meter, I  fixed  a  wire  a  foot  and  a  half  long.  This  wire  termi- 
nated in  four  ramifications,  each  of  which  was  fixed  to  a 
metallic  ball  half  an  inch  in  diameter,  and  placed  at  an 
equal  diftance  from  a  metallic  plate,  which  communicated  by 
metallic  condu6lors  with  the  ground.  A  powerful  fpark,  after 
falling  on  the  large  ball  at  one  extremity  of  the  wire,  was 
divided  in  its  paffage  from  the  four  fmall  balls  to  the  metallic 
plate.  When  I  examined  this  divifion  of  the  fluid  in  a  dark 
room,  I  difcovered  fome  little  ramifications  which  yielded  the 
indigo  rays  only :  indeed,  at  the  edges  of  all  weak  fparks  the 
fame  purple  appearance  may  be  difcovered.  We  may  likewife 
obferve,  that  the  nearer  we  approach  the  center  of  the  fpark,. 
the  greater  is  the  brilliancy  of  its  colour.  But  I  would  now 
wifh  to  (hew 

6.  That  the  influence  of  different  media  on  electrical  light 
is  analogous  to  their  influence  on  folar  light,  and  will  help  us 
to  account  for  fome  very  Angular  appearances. 

EXP. XII.  Let  a  pointed  wire,  having  a  metallic  ball  fixed  to  one 
of  its  extremities,  be  forced  obliquely  into  a  piece  of  wood,  fo  as 
to  make  a  fmall  angle  with  the  furface  of  the  wood,  and  to  make 

*  If  the  Torricellian  vacuum  is  made  with  mercury  perfeftly  purged  of  air,  it 
becomes  a  perfect  non-condu6lor.  This,  I  believe,  will  be  proved  decifively  by 
iftme  experiments  whicli  I  hope  will  be  foon  communicated  to  the  Royal  Society. 

Dr.  Price. 

I  the 


the  Light  of  Bodies  in  a  State  of  Combufion,  2© 5 

the  point  He  about  onc-elghth  of  an  inch  below  the  furfac;-. 
Let  another  pointed  wire,  which  communicates  with  the  ground^ 
be  forced  in  the  fame  manner  into  the  lame  wood,  fo  that 
its  point  likewife  may  He  about  one-eighth  of  an  inch  below 
the  furface,  and  about  two  inches  dlfiant  from  the  point  of 
the  firft  wire.  Let  the  wood  be  infulated,  and  a  ftrong  Ipark 
which  il:rikes  on  the  metaUic  ball  will  force  its  paliage  through 
the  interval  of  wood  which  lies  between  the  points,  and  appear 
as  red  as  blood.  To  prove  that  this  appearance  depends  on  the: 
wood's  abforption  of  all  the  rays  hut  the  red,  I  would  obferve, 
that  the  greater  the  depth  of  the  points  is  below  the  furface,  the 
lefs  mixed  are  the  red  rays.  I  have  been  able  fometimes,  by  in- 
creafnig  or  diminifliing  the  depth  of  the  points,  to  give  the 
fpark  the  following  fucceflion  of  colours.  When  they  were 
deepeft  below  the  lurface,  the  red  only  came  to  the  eye  through 
a  prifm.  When  they  were  raifed  a  little  nearer  the  furface, 
the  red  and  orange  appeared.  When  nearer  ftill,  the  yellow  ; 
and  fo  on  till,  by  making  the  fpark  pafs  through  the  wood  very 
near  its  furface,  all  the  rays  were  at  length  able  to  reach  the 
eye.  If  the  points  be  only  one-eighth  of  an  inch  below  the 
fiarface  of  foft  deal  wood^  the  red,  the  orange,  and  the  yel- 
low rays  will  appear  as  the  fpark  pafles  through  it.  But  whea 
the  points  are  at  an  equal  depth  in  a  harder  piece  of  wood  (fuch. 
as  box)  the  yellow,  and  perhaps  the  orange,  will  difappear.  Aa. 
a  farther  proof  that  the  phifinomena  I  am  defcribing  are  owing  to 
the  interpofition  of  the  wood,  as  a  medium  which  abforbs  fome 
of  the  rays  and  fufFers  others  to  efcape,  it  may  be  obferved,  that 
when  the  fpark  ftrikes  very  brilliantly  on  one  fide  of  the  piece 
of  deal,  on  the  other  fide  it  will  appear  very  red.  In  like  man- 
ner a  red  appearance  may  be  given  to  a  fpark  which  ftrikes, 

hrilUaiitly 


2o6       Mr.  Morgan's  ObfervatJons  and  Experiments  on 

brilliantly  over  the  infide  of  a  tube,  merely  by  fpreading  fome. 
pitch  VQvy  thinly  over  the  outfide  of  the  fame  tube. 

EXP.  XIII.  I  would  now  give  another  fa6l,  whofe  Angulari- 
ties depend  very  much  on  the  influence  Oi  the  medium  through 
which  the  eletftrical  light  is  made  to  pafs.  If  into  a  Torricel- 
lian vacuum,  of  any  length,  a  few  drops  of  aether  are  conveyed, 
and  both  ends  of  the  vacuum  are  (lopped  up  with  metallic  con- 
dudlors,  fo  that  a  fpark  may  pafs  through  it,  the  fpark  in  its 
paflage  will  affume  the  following  appearances.  When  the  eye 
is  placed  clofe  to  the  tube,  the  Ipark  will  appear  perfe6lly 
white.  If  the  eye  is  removed  to  the  diftance  of  two  yards,  it 
will  appear  green  ;  but  at  the  diftance  of  fix  or  feven  yards, 
the  colour  of  the  fpark  will  be  reddifli.  Thefe  changes  evi- 
dently depend  on  the  quantity  of  medium  through  which  the 
the  light  paiies ;  and  the  red  light  mxore  particularly,  which 
we  fee  at  the  greatefl:  diftance  from  the  tube,  is  accounted  for 
on  the  fame  principle  as  the  red  light  of  a  didant  candle  or  a 
beclouded  fun. 

EXP.  XIV.  Dr.  Priestley  long  ago  obferved  the  red  ap- 
pearance of  the  fpark  when  paffing  through  inflammable  air. 
But  this  appearance  is  very  much  diverfified  by  the  quantity  of 
medium,  through  which  you  look  at  the  fpark.  When  at  a 
very  confiderable  diftance,  the  red  comes  to  the  eye  unmixed  j 
but,  if  the  eye  is  placed  clofe  to  the  tube,  the  fpark  appears 
white  and  brilliant.  In  confirmation,  however,  of  fome  of 
my  conclufions,  I  Vv^ould  obferve,  that  by  increafing  *the 
quantity  of  fluid  which  is  conveyed  through  any  portion 
of  inflammable  air,  or  by  condenfing  that  air,  the  fpark  may 
be  entirely  deprived  of  its  red  appearance,  and  made  perfedly 
brilliant.     I  have  only  to  add,  that  all  weak  explofions  and 

fparks, 


ihe  Light  of  Bodies  in  a  State  of  Combufiion,  207 

fpnrks,  when  viewed  at  a  didance,  bear  a  rcddifh  hue.  Such 
arc  tlie  explofioiis  which  have  pailed  through  water,  I'piiits  of 
wine,  or  T.ny  bad  condudor,  when  confined  in  a  tube  whofe 
diameter  is  not  more  than  an  inch.  The  reafon  of  tlicfe 
appearances  Teems  to  be,  that  the  weaker  the  fpark  or  explofioii 
is,  the  lefs  is  the  iiglit  which  efcapes ;  and  the  more  vifible 
the  effe6t  of  any  medium  which  has  a  powder  to  abforb  fomc  of 
that  light. 

The  preceding  obfervations  concerning  ele(5lrical  h!ght  were 
the  refult  of  my  attempts  to  arrange,  under  general  heads, 
the  principal  fingularities  attending  it.  They  may,  perhaps, 
affifl  others  in  determining  how  far  they  may  have  led  my  mind 
aftray  in  giving  birth  to  a  theory  wiiich  I  would  now  briefly 
defcribe  in  a  few  queries. 

I.  If  we  confider  all  bodies  as  compounds,  whofe  confrituent 
parts  are  kept  together  by  attracting  one  another  with  different 
forces,  can  we  avoid  concluding,  that  the  operations  of  that 
attradive  force  are  regulated,  not  only  by  the  quality,  but  the 
quantity likewife  of  thofe  component  parts?  If  an  union  of  a 
certain  number  of  one  kind  ot  particles,  with  a  certain  num- 
ber of  a  fecond  and  third  kind  of  particles,  forms  a  particular 
body,  mufi:  not  the  bond  which  keeps  that  body  together  be 
weakened  or  ftrengthened  by  Incrcafmg  or  diminiiliing  any  one 
of  the  different  kinds  of  particles  which  enter  into  its  confti- 
tution  ? 

II.  When,  to  the  natural  fhare  of  the  eledric  fluid  al- 
ready exifting  in  the  body,  a  frefli  quantity  of  the  fame 
fluid  is  added,  muft  not  fome  of  the  component  parts  of  that 
body  efcape  ;  or  muf!:  not  that  attractive  force  which  kept  all 
toaether  be  fo  far  weakened  as  to  let  loofe  fome  conllituent 

part5p. 


20 S       Mi'\  MogGAN*s  QS/erva^ms  and  Experiments  an 

parts,    and   amongft  thefe    the    paiticlea  of  light    in    parti* 
cilia r  ? 

III.  Mufl;  not  this  feparation  of  parts  be  great  ia  proportion 
to  the  quantity  of  extraneous  particles  which  are  added  to  the 
body  ?  Or  (agreeable  to  the  4th  obfervation)  muil:  not  the 
fpark  be  more  fplendid  and  brilliant,  the  more  the  ele6;rical 
fluid  is  concentered  in  any  given  fpace  ? 

IV.  In  the  diminution  or  alteration  of  that  attradive  force  ors 
which  depends  the  conftitution  of  bodies,  may  there  not  be  a 
gradation  which,  in  the  prefent  cafe,  as  well  as  in  that  of 
burning  bodies,  will  caufe  the  efcape  of  fome  rays  fooncr  than 
others  ? 

Ohfervations  on  pJoofphoj-ic  light. 

It  is  obvious,  from  Mr.  B.  Wilson's  experiments,  that 
there  are  many  curious  diverfities  in  the  appearances  of  phof- 
phori.  Some  (hells,  prepared  ngrccably  to  his  diredlons,  after 
expbfure  to  the  fun  or  to  the  flafh  of  a  battery,  emit  a  purple, 
others  a  green,  and  others  a  reddifh  light.  If  wdth  Mr.  Wil- 
son we  fuppofe,  that  thefe  fliells  are  in  a  ftate  of  flow  com- 
buflion,  may  we  not  conclude,  that  fome  arejull;  beginning  to 
burn,  and  therefore,  agreeably  to  what  I  haveobferved  on  com- 
buftlble  bodies,  emitting  the  mod:  refrangible  rays;  whilft  others 
are  in  a  more  advanced  flate  of  combuftion,  and  therefore 
emitting  the  leaft  refrangiible.  If  this  conclufion  be  right, 
the  fhells  which  are  emitting  the  purple,  or  the  green,  mufl 
ftill  retain  the  yellow,  the  orange,  and  the  red,  which  will 
alfo  make  their  appearance  as  foon  as  the  combuftion  is  fuffi- 
dently  increafed. 

EXP. 


ibe  "Ltght  of  Eodks  in  u  State  of  Comb ujl ton,  ■20.9 

e:XP.  XV.  Place  a  fliell  vvhllfl  emitting  its  green  rays  on  a 

warm    fhovel,  and  the  appearance   of  the  fhell  will  be  foou 

cl^anfred  into  that  of  a  veilow  mixed  with  red.     To  Mr.  Wil- 

-son's  theory,  hou^ever,  of  (low  combuftion  the  following  ob- 

j-e6lions  may  be  oppoled. 

i''.  If  phofphoric  (hells  owe  their  light  to  this  caufe,  wc 
muft  confider  the  word  combuftion  when  applied  to  them  as 
implying  in  its  iignilication  all  thofe  circumftances  which  are 
the  ufual  attendants  of  a  body  whilft  on  fire.  Amongfl:  other 
iieceirary  confequences  in  fuch  a  cafe,  the  increafe  of  heat  muft 
increalc  the  decompofition  of  the  combuftible ;  whereas  we 
•difcover  an  etl^^t  the  very  oppolite  to  this  in  the  appearance  of 
a  phofphoric  body,  which  never  fails  to  lofe  its  light  entirely 
in  a  certain  degree  of  heat,  without  lohng  the  power  of  be- 
^coming  phofphoric  again  when  it  has  been  fufficiently  cooled. 
Befides,  when  a  phofphoric  ihell  has  been  made  very  hot,  and 
while  it  has  continued  fo,  I  have  conveyed  the  moft  brilliant 
difcharge  of  a  battery  over  it  without  efFe(^.  In  other  words, 
heat,  or  the  very  caufe  which  promotes  combuftion  in  all  other 
inftances,  in  this  particular  cafe  puts  an  end  to  it.  Mr.  Wil- 
son, in  his  Treatife  on  Phofphori,  has  defcribed  an  experiment 
fimilar  to  the  preceding.  But  the  refulthe  mentions  is  different 
from  that  here  mentioned.  However,  from  a  regard  to  his 
authority,  I  have  fo  frequently  repeated  my  trials  that  I  cannot 
juftly  fufpe<5l  myfelf  of  any  inaccuracy.  2\  When  bodies 
are  wafled  by  combuftion,  they  can  never  be  made  to  re-affume 
the  appearances  which  they  previoufly  difplayed.  No  power 
can  give  to  alhes  the  phenomena  of  a  burning  coal.  But 
phofphoric  bodies  are  very  different  in  this  refpe<5t ;  for  a  fhell 
may  be  made  to  lofe  all  its  light  by  expofure  to  heat,  and  again 
.  Vol.  LXXV.  E  e  may 


210        Mr.  Morgan's  Ohfefuat'.ons  and  Experiments  on 

may  be  made  as  Inminous  as  ever  by  expofure  to  the  fun.  But 
2^.  It  is  obfervable,  that  fome  bodies,  which  are  moO:  beau- 
tifully phofphoric,  or  which,  according  to  Mr.  Wilson*s 
theory,  are  in  the  bed  Aate  of  flow  combuftion  ;  it  is  obfervable, 
I  fay,  that  the  fame  bodies  are  the  moftobftinate  in  refifting  the 
fire.  The  diamond,  which  to  be  decompofed  requires  the 
force  of  a  mofi:  powerful  furnace,  is,  according  to  this 
theory,  wailing  away,  owing  to  a  feparation  of  parts  which 
is  promoted  by  the  weakeft  influence  of  the  fun's  rays. — With- 
out determining  whether  the  p>recedmg  obje6lions  be  valid,  let  us 
now  fee  the  confequence  of  admitting  the  common  hypothecs, 
that  the  detention  of  tbofe  rays  which  fall  upon  phofphori  is 
owing  to  fome  force  which  prevents  their  immediate  reflection, 
but  is  not  adequate  to  their  entire  abforption.  This  force, 
whatever  it  be,  cannot  well  be  fuppofed  to  operate  with  equal 
power  on  all  the  rays.  And  if  this  be  not  the  cafe,  I  think 
we  cannot  avoid  concluding,  that  phofphoric  fhells  will  afliime 
-r  different  colours,  owing  to  the  earlier  and  later  efcape  of  the 
different  rays  of  light.  This  conclufion  is  juftified  by  an  expe- 
riment which  I  have  already  appealed  to.  When  the  force  is 
f  ich  as  to  admit  of  the  efcape  of  the  purple,  the  blue,  and.  the 
green,  we  have  only  to  leffen  that  force  by  warming  the  bodv, 
and  the  yellow,  the  orange,  and  red  efcape.  It  is  proved  by 
Beccaria's  extenfive  experience  on  this  fubj.ft,  that  there  is 
fjarcely  any  body  which  is  not  phofphoric,  or  which  may.  not 
be  made  fo  by  heat.  But  as  the  phofphoric  force  is  moft 
powerful  when  the  purple  rays  only  efcape,  fo  we  are  to- con- 
clude, that  it  is  weakeft  when  it  is  able  to  retain  the  red  rays  only. 
This  conclufion  is  agreeable  to  fevcral  faCls.  Chalk,  oyfter- 
thells,  together  w^ith  thofe  phofphoric  bodies  whofe  goodnefs 
7  has 


the  Light  of  Bodies  in  a  State  of  Conibufion*  2 1 1 

has  been  very  mucli  impaired  bv  long  keeping;  when 
finely  powdered  and  placed  within  the  circuit  of  an  elcdrical 
batter}',  will  exhibit  by  their  fcattered  particles  a  fliowTr 
of  light;  but  tliefe  particles  will  appear  reddilh,  or  their 
phofphoric  power  will  be  fufficient  only  to  detain  the 
yellow,  orange,  and  red  ravs.  When  fpirits  of  wine  are  in  a 
iimilar  manner  brought  within  the  circuit  of  a  battery,  a 
fimilar  efte6l  may  he  difcovered  ;  its  particles  diverge  in  feveral 
direftions,  dilplaying  a  moft  beautiful  golden  appearance.  The 
metallic  calces  are,  of  all  bodies,  thofe  which  are  rendered 
phofphoric  with  the  greateft  difficulty.  But  even  thefe  may 
be  fcattered  into  a  fhower  of  red  luminous  particles  by  the 
electric  ftroke. 

JC'orwich,  Oct.  7,   1784, 


POSTSCRIPT    by  the  Rev.  Dr.  Price. 

BY  the  phofphoric  force  mentioned  in  the  laft  paragraph  of 
this  paper,  Mr.  Morgan  appears  to  mean,  not  the  force  with 
which  a  phofphoric  body  emits,  but  the  force  with  which  it 
abforbs  and  retains  light.  This  laft  force  is  proportioned 
to  the  degree  of  attra6tion  between  the  phofphoric  body  and 
light ;  and  therefore  muft  (as  Mr.  Morgan  obferves)  be 
iveakefi  when  it  emits  fo  freely  the  light  it  has  imbibed  as  not 
to  retain  thofe  rays  which  adhere  to  it  moft  ftrongly.  Ac- 
cording to  Mr.  Morgan's  theory,  thefe  rays  ^re  thofe  which 

E  e  2  arc 


ii2     Mr>  Morgan's  Obfervatlons  and  Experiments,  Sec, 
am  leafl   refrangible.     The  obfervatlons  and  experiments   hir 
this  paper  feem  to  render  this  theory  probable.     It  is,  how- 
ever, an    objeaion    to    it,  that  the  lefs   refrangibility  of  rays- 
feems  to  imply  a  lefs  force  of  attradion  between  them  and  the. 
fubftances .  which  refrad  them  ;  but  it  fnould   be   confidered-, 
that,    polTibly,  the   force  of  cohefion,,  which    unites  the  rays 
of  light  to  bodies,  may  be  a  different  power  from  that,  wluch.. 
refra£is  thera^. 


[    213    ] 


Xir.  0;;  the  ConJlruBlon  cf  the  Heave tn. 
By  VVilllam  Ilerichcl,  Efq.  F.  R.  S. 


Read  February  3,   i/^i'* 

Tn  E  fubje£l  of  the  Coiifrriicllon  of  the  Heavens,  on 
which  I  have  fo  lately  ventured  to  deliver  my  thoughts 
to  this  Society,  is  of  fo  extenllve  and  important  a  nature,  that 
we  cannot  exert  too  much  attention  in  our  endeavours  to  throw 
all  poffible  light  upon  it;  I  fhall,  therefore,  now  attempt 
to  pi.rfue  the  delineations  of  wliich  a  faint  outline  was  begun 
iu  my  former  paper. 

By  continuing  to.  oblerve  the  heavens  with  my  laft  con- 
ftruvfled,  and  fmce  that  time  much  improved  inftrument,  I  aai 
now  enabled  to  bring  more  confirmation  to  feveral  parts  that 
were  before  but  weakly  fupported,  and  alfo  to  offer  a  few  {k.[\l 
further  extended  hints,  fuch  as  they  prefent  themfelves  to  my 
prefent  view.  But  firft  let  me  mention  that,  if  we  would 
hope  to  make  any  progrefs  in  an  invefligation  of  this  delicate 
nature,  we  ought  to  avoid  two  oppofite  extremes,  of  which  I 
can  hardly  fay  which  is  the  moft  dangerous.  If  we  indulge  a 
fanciful  imagination  and  build  worlds  of  our  own,  we  muft 
not  wonder  at  our  going  wide;  from  the  path  of  truth  and 
nature ;  but  thefe  will  vanifh  like  the  Cartefian  vortices,  that 
foon  gave  way  when  better  theories  were  offered.  On  the  other 
hand,  if  we  add  obfervation  to  obfervation,  without  attempt- 
ing to  draw  not  only  certain  conclufions;  but  alfo  conjedural 

views 


2 14  Mr.  Herschel  on  the 

views  from  them,  we  offend  again il:  the  verj  end  for  which 
only  obfervations  ought  to  be  made.  I  will  endeavour  to  keep 
a  proper  medium  ;  but  if  I  fhould  deviate  from  that,  I  could 
wilh  not  to  fall  into  the  latter  error. 

That  the  milky  way  is  a  mofl:  extenfive  (Iratum  of  flars  of 
various  fizes  admits  no  longer  of  the  lead:  doubt ;  and  that  our 
fun  is  actually  one  of  the  heavenly  bodies  belonging  to  it  is  as 
evident.  I  have  now  viewed  and  gaged  thl«  Ihining  zone  in 
almoft  every  direction,  and  find  it  compofed  of  flars  whofe 
number,  by  the  account  of  thefe  gages,  conftantly  increafes 
and  decreafes  in  proportion  to  its  apparent  brightnefs  to  the 
naked  eye.  But  in  order  to  develop  the  ideas  of  the  univerfe, 
that  have  been  fuggefled  by  my  late  obfervations,  it  will  be  beft 
to  take  the  fubjecl  from  a  point  of  view  at  a  confidcrable 
diflance  both  of  fpace  and  of  time. 

Theoretical  view. 

Let  us  then  fuppofe  numbcrlefs  ftars  of  various  fizes,  feat- 
tered  over  an  indefinite  portion  of  fpace  in  fuch  a  rrianner  as  to 
be  almoft  equally  diftributed  throughout  the  whole.  The  laws 
of  attra6lion,  which  no  doubt  extend  to  the  rcmoteft  regions  of 
the  fixed  ftars,  will  operate  in  fuch  a  manner  as  moft  probably  to 
produce  the  following  remarkable  effedts. 

^''  Formation  of  nebiilce. 

Form  I.        In  the  firft  place,  ftnce  we  havcfuppofed  the  ftars 

to  be  of  various  fizes,  it  will  frequently  happen  that  a  ftar, 

being    confiderably    larger   than    its    neighbouring  ones,    will 

attract  them  more  than  they  will  be  attra«fted  by  others  that  are 

-■sj.;^:.;  immediately 


Ojfrflruclion  of  the  Heavens.  2 1  ^ 

immediately  around  them  ;  by  which  means  they  will  be,  in 
time,  as  it  were,  condenfed  about  a  center  ;  or,  in  other  words, 
form  themfelves  into  a  cluftcr  of  ftars  of  almoft  a  globular 
figure,  more  or  lefs  regularly  fo,  according  to  the  fize  and 
original  diftancc  of  the  furrounding  ftars.  The  perturbations 
of  thefe  mutual  attractions  mufl  undoubtedly  be  very  intricate, 
as -"we  may  eafily  comprehend  by  confidering  what  Sir  Isaac 
Newton  lays  in  the  firft  book  of  his  Principia,  in  the  38th 
and  folio vving  problems;  but  in  order  to  apply  this  great 
author's  reafoning  of  bodies  moving  in  ellipfes  to  fuch  as  are 
here,  for  a  while,  fuppofed  to  have  no  other  motion  than  what 
their  mutual  gravity  has  imparted  to  them,  we  mufl:  fuppofe 
the  conjugate  axes  of  thefe  elliples  indefinitely  diminiflied, 
whereby  the  ellipfes  will  become  ftraight  lines. 

Form  IL  The  n^xt  cafe,  which  will  alfo  happen  aimoft  as 
frequently  as  the  former,  is  where  a  few  fl-ars,  though  not 
fuperior  in  fize  to  the  reft,  may  chance  to  be  rather  nearer  each 
other  than  the  furrounding  ones  j  for  here  alfo  will  be  formed  a 
prevailing  attraction  in  the  combined  center  of  gravity  of  them 
all,  which  will  occafion  the  neighbouring  flars  to  draw  toge- 
ther ;  net  indeed  fo  as  to  form  a  regular  or  globular  figure,  but 
however  in  fuch  a  manner  as  to  be  condenfed  towards  tlie 
common  center  of  gravity  of  the  Vv^iole  irregular  elufler.  And 
this  conflruClion  admits  of  the  utmofl:  variety  of  Ihapes,  ac- 
cording; to  the  number  and  fiJuation  of  the  ftars  which  firfi: 
gave  rife  to  the  condenfation  of  the  refl. 

Form  111.  From  the  compofition  and  repeated  conjuniTcion 
of  both  the  foreooin":  forms,  a  third  may  be  derived,  w^henmanv 
large  flars,  or  combined  fmall  ones,  are  fituated  in-  long  ex- 
tended, regular,  or  crooked  rows,  hooks,  or  branches  ;  for  they 
will  alfa  draw  the  furrounding  ones,  fo  as  to  produce  figurejy 

of 


21 6  Mr.  Herschel  on  the 

of  condenfed  ftars  coarfely  fimilar  to  the  former  which   gave 
rife  to  thcfe  condenflitioiis. 

•Form  IV.  We  may  Hkevvife  admit  of  ftill  more  extenfive^ 
combinations;  when,  at  the  fame  time  that  a  chafter  of  fiars 
is  forming  in  one  part  of  fpace,  there  may  be  another  coUecl- 
}X\^  in  a  different,  but  perhaps  not  far  diftant  quarter,  which 
may  occafion  a  mutual  approach  towards  their  common  center 
of  gravity, 

V.  In  the    laft  place,  as  a  natural  confequence  of  th« 

former  cafes,  there  will  be  formed  great  cavities  or  vacancies 
by  the  retreat  of  the  ftars  towards  the  various  centers  which 
attrad:  them  ;  fo  that  upon  the  whole  there  is  evidently  a  field 
of  the  greateft  variety  for  the  mutual  and  combined  attractions 
of  the  heavenly  bodies  to  exert  themfelves  in.  -I  ihall,  there- 
tore,  without  extending  myfelf  farther  upon  this  fubjed:,  pro- 
ceed to  a  few  coiifidcrddons,  that  will  naturally  occur  to  every 
'OWQ  who  may  view  this  fubject  in  the  light  I  have  here  done. 

Ohjedliom  cojijiderea. 

'Atfirfl:  f3ght  then  it  will  feem  as  if  a  fyilem,  fuch  as  it  has 
been  difplayed  in  the  foregoing  paragraphs,  would  evidently 
tend  to  a  general  deftrudion,  by  the  fhock  of  one  flar's 
falling  upon  another.  It  would  here  be  a  fufficient  anfwer  to 
fay,  that  if  obfervation  fliould  prove  this  really  to  be  the 
fyftem  of  the  univerfe,  there  is  no  doubt  but  that  the  great 
Author  of  it  has  amply  provided  for  the  prefervation  of  the 
whole,  though  it  fhould  not  appear  to  us  in  what  manner  this 
is  effetSled.  But  I  (hall  moreover  point  out  feveral  circum- 
;Ilances  that  do  manifeftly  tend  to  a  general  prefervation  ;  as,  in 
ithe  firft  place,  the  indefinite  extent  of  the  iidereal  heavens, 

6  which 


Conjiruditon  of  the  Heavens.  217 

which  miift  produce  a  balance  that  will  effedually  fecure  all 
the  great  parts  of  the  whole  from  approaching  to  each  other. 
There  remains  then  only  to  fee  how  the  particular  ftars  be- 
longing to  feparate  clufters  will  be  preferved  from  rufliing  on 
to  their  centers  of  attraction.     And  here  I  muft  obferve,  that 
thougli  I  have  before,  by  way  of  rendering  the  cafe  more  fim- 
ple,  confidered  the  ftars  as  being  originally  at  reft,  I  intended 
not  to  exclude  projectile  forces ;  and  the  admiffion  of  then* 
will  prove  fuch  a  barrier  againft  the  feeming  deftruClive  power 
of  attraction  as  to  fecure  from  it  all  the  flars  belonging  to  a 
clufter,  if  not  for  ever,  at  leafl  for  millions  of  ages      Befides, 
we  ought  perhaps  to  look  upon  fuch  clufters,  and  the  deftruc- 
tion  of  now   and  then  a  (tar,  in  fome  thoufands  of  ages,  as 
perhaps  the  very  means  by  which  the  whole  is  preferved  and 
renewed.  Thefe  clufters  may  be  the  L^^^^r^/or/Vjoftheuniverfe^ 
if  I  may  fo  exprefs  myfelf,  wherein  the  mofl  falutary  remedies 
for  the  decay  of  the  whole  are  prepared. 

Optical  appearances. 

From  this  theoretical  view  of  the  heavens,  which  has  been 
taken,  as  we  obferved,  from  a  point  not  lefs  diftant  in  time 
than  in  fpace,  we  will  now  retreat  to  our  own  retired  flation, 
in  one  of  the  planets  attending  a  ftar  in  its  great  combination 
with  numberlefs  others ;  and  in  order  to  inveftigate  what  will 
be  the  appearances  from  this  contracted  fituation,  let  us  begin 
with  the  naked  eye.  The  ftars  of  the  firft  magnitude  being 
in  all  probability  the  neareft,  will  furnilh  us  with  a  ftep  to 
begin  our  fcale ;  fetting  off,  therefore,  with  the  diftance  of 
Sirius  or  ArCturus,  for  inftance,  as  unity,  we  will  at  prefent 
fuppofe,  that  thofe  of  the  fecond  magnitude  are  at  double,  and 

Vol.  LXXV.  F  f  thofc 


2.8  Mr,  Herschel  on  the 

thofe  of  the  third  at  treble  the  diftnnce,  and  fo  forth.  It  is  not 
neceffary  critically  to  examine  what  quantity  of  light  or  mag- 
nitude of  a  ftar  intltles  it  to  be  eftimated  of  fuch  or  fuch  a  pro- 
portional diftance,  as  the  common  coarfe  eftimation  will  anfwer 
our  prefent  purpofe  as  well;  taking  it  then  for  granted,  that  a 
flar  of  the  feventh  magnitude  is  about  fcven  times  as  far  as 
one  of  the  hrft,  it  follows,  that  an  obferver,  who  is  inclofed 
an  a  globular  cl after  of  ftars,  and  not  far  from  the  center,  will 
never  be  able,  with  the  naked  eye,  to  fee  to  the  end  of  it :  for,, 
iince,  according  to  the  above  eftimations,  he  can  only  extend  his 
view  to  about  feven  tunes  the  diftance  of  Sirius,  it  cannot  be 
expelled  that  his  eyes  fhould  r?ach  the  borders  of  a  clufter 
which  has  perhaps  not  lefs  than  fifty  flars  in  depth  every  where 
around  him.  The  whole  univerfe,  therefore,  to  him  will  be 
comprifed  in  a  fet  of  conftellations,  richly  ornamented  with 
fcattered  ftars  of  all  fizes.  Or  if  the  united  brightnefs  of  a 
neighbouring  clufter  of  ftars  fliould,  in  a  remarkable  clear 
night,  reach  his  fight,  it  will  put  on  the  appearance  of  a  fmall, 
faint,  whitifti,  nebulous  cloud,  not  to  be  perceived  without 
the  greateft  attention.  To  pafs  by  other  lituations,  let  him 
be  placed  in  a  much  extended  ftratum,  or  branching  clufter  of 
millions  of  ftars,  fuch  as  may  fall  under  the  IIF  form  of  ne- 
bulae conftdered  in  a  foregoing  paragraph.  Here  alfo  the  hea- 
vens will  not  only  be  richly  fcattered  over  with  brilliant  con- 
ftellations, but  a  ftiinlng  zone  or  milky  way  will  be  perceived 
to  furround  the  whole  fphere  of  the  heavens,  owing  to  the 
combined  light  of  thofe  ftars  which  are  too  fmall,  that  is,  too 
remote  to  be  feen.  Our  obferver's  fight  will  be  fo  confined, 
that  he  will  imagine  this  fingle  colleftion  of  ftars,  of  which  he 
does  not  even  perceive  the  thoufandth  part,  to  be  the  whole 
contents  of  the  heavens.  Allowing  him  now  the  ufe  of  a 
4  common 


Conjlrudlion  of  the  Heavens >  219 

common  telefcope,  he  begins  to  fufpeft  that  all  the  milkuiefs 
of  the  bright  path  which  furrounds  the  fphere  may  be  owing 
to  ftars.  He  perceives  a  few  cluflers  of  them  in  various  parts 
of  the  heavens,  and  finds  alfo  that  there  are  a  kind  of  nebu- 
lous patches  ;  but  ftill  his  views  are  not  extended  fo  far  as  to 
reach  to  the  end  of  the  ftratum  in  which  he  is  fituated,  fo  that 
he  looks  upon  thefe  patches  as  belonging  to  that  fyflem  which 
to  him  feems  to  comprehend  every  celeftial  objed:.  He  now 
increafes  his  power  of  vifion,  and,  applying  himfelf  to  a  clofe 
obfervation,  finds  that  the  milky  way  is  indeed  no  other  than  a 
collection  of  very  fmall  ftars.  He  perceives  that  thofe  objects 
which  had  been  called  nebulae  are  evidently  nothing  but  cluflers 
of  ftars.  He  finds  their  number  increafe  upon  him-,  and  when 
he  refolves  one  nebula  into  ftars  he  difcovers  ten  new  ones 
which  he  cannot  refolve,  He  then  forms  the  idea  of  immenfe 
flrata  of  fixed  ftars,  of  cluftersof  ftars  and  of  nebulas  {a)  ;  till, 
going  on  with  fuch  interefting  obfervation s,  he  now  perceives 
that  all  thefe  appearances  muft  naturally  arife  from  the  con- 
fined fituation  in  which  we  are  placed.  Confined  it  may  juitly 
be  called,  though  in  no  lefs  a  fpace  than  what  before  appeared 
to  be  the  whole  region  of  the  fixed  ftars ;  but  which  now  has 
affumed  the  ihape  of  a  crookedly  branching  nebula ;  not,  in- 
deed, one  of  the  leafl,  but  perhaps  very  far  from'  being  the 
mofl  confiderable  of  thofe  numberlefs  clufters  that  enter  into 
the  conftrudtion  of  the  heavens. 

Refuit  of  ObfervationSi 

1  (hall  now  endeavour  to  fhew,  that  the  theoretical  view  of 
the  fyftem  of  the  univerfe,  which   has  been  expofed  in   the 
{a)  See  a  former  paper  on  the  Conftruftion  of  the  Heavens. 

F  f  2  fore- 


220  Mr.  Herschel  on  the 

foregoing  part  of  this  paper,  is  perfectly  confiftent  with  h€t% 
and  feems  to  be  confirmed  and  eflabUfhed  by  a  feries  of  obfer- 
vations.  It  will  appear,  that  many  hundreds  of  nebulae  of  the 
firft  and  fecond  forms  are  actually  to  be  ittw  in  the  heavens, 
and  their  places  will  hereafter  be  pointed  out.  Many  of  the 
thtid  form  will  be  defcribed,  and  inftances  of  the  fourth  re- 
lated. A  few  of  the  cavities  mentioned  in  the  fifth  will  be 
particularifed,  though  many  more  have  already  been  obfcrved ; 
fo  that,  upon  the  w^holc,  I  believe,  it  will  be  found,  that  the 
foregoing  theoretical  view,  with  all  its  confequential  appear- 
ances, as  feen  by  an  eye  inclofed  in  one  of  the  nebulae,  is  no 
other  than  a  drawing  from  nature,  wherein  the  features  of  the 
original  have  been  clofely  copied  ;  and  1  hope  the  refemblance 
will  not  be  called  a  bad  one,  when  it  fliall  be  confidcred  how" 
very  limited  mufl:  be  the  pencil  of  an  inhabitant  of  fo  fmall 
and  retired  a  portion  of  an  Indefinite  fyftem  in  attempting  the 
picture  of  fo  unbounded  an  extent. 

But  to  proceed  to  particulars  :  I  fhall  begin  by  giving  the 
following  table  of  gages  that  have  been  taken.  In  the  firft 
column  is  the  right  afcenfion,  and  in  the  fecond  the  north 
polar  diflance,  both  reduced  to  the  time  of  Flamsteed's 
Catalogue.  In  the  third  are  the  contents  of  the  heavens,  being 
the  refult  of  the  gages.  The  fourth  fhews  from  how  many 
fields  of  view  the  gages  w^ere  deduced,  which  have  been  ten  or 
more  where  the  number  of  the  ftars  was  not  very  confiderable ; 
but,  as  it  would  have  taken  too  much  time,  in  high  numbers, 
to  count  fo  many  fields,  the  gages  are  generally  fingle.  Where 
the  ftars  happened  to  be  uncommonly  crouded,  no  more  than 
half  a  field  was  counted,  and  even  fometimes  only  a  quadrant ; 
but  then  it  was  always  done  with  the  precaution  of  fixing  on 
fome  row  of  ftars  that  would  point  out  the  divifion  of  the  field, 

fo 


Conjlrudlion  of  the  Heavens.  221 

fo  as  to  prevent  any  conlidcrable  miftake.  When  five,  ten,  or 
more  fields  are  gaged,  the  polar  diftance  in  the  fecond  column 
of  the  table  is  that  of  the  middle  of  the  fvveep,  which  was 
generally  from  2  to  2t  degrees  in  breadth;  and,  in  gaging,  a 
regular  diftribution  of  the  fields,  from  the  bottom  of  the  fweep 
to  the  top,  was  always  ftridly  attended  to.  The  fifth  column 
contains  occafional  remarks  relating  to  the  gages. 

I.  Table  of  Star-Gages. 


R.A. 

P.D.          Stars. 

Fields. 

Memorandums, 

H.  M.  S 

D.  M. 

0     I  41 

78  47 

9.9 

10 

0    4  55 

65  36 

20,0 

10 

0     7  54 

74  13 

ii'3 

10 

Moft  of  the  ftars  extremely  fmall. 

0     8  24 

49     7 

60 

I 

0     9  52 

113  17 

4,1 

10 

%  The   gages  marked  with    an  afterilk 

0  12  52 

113  17 

3.2 

10 

;f               are  thofe  by  which  fig.  4.  tab. 

0  16  48 

67  44 

11,9 

10 

Vlll.  has  been  delineated. 

0  21  52 

113  17 

3.9 

10 

^ 

0  22  21 

87  10 

5,9 

10 

0  28  26 

46  54 

60 

I 

0  31  38 

46  54 

40 

1 

0  Z3  33 

65  32 

20,4 

10 

0  34  22 

56  38 

20 

I 

0  35  22 

55  38 

24 

I 

0  36  39 

76  32 

"»3 

10 

0  39  56 

78  43 

8,1 

10 

0  40  29 

48  43 

60 

1 

0  44  21 

87   10 

7,6 

10 

0  46  22 

69  51 

II 

10 

0  46  33 

65  32 

13 

10 

0  48  42 

58  47 

40 

I 

0  48  50 

58  13 

17 

I 

P  53  18 

67  41 

9,8 

10 

A  little  hazy. 

0  53  40 

45  37 

73 

I 

0  54  10 

75.16      13      1 

I 

xvoA.. 


"222 


Mr\  Hesschel  on  the 


R.A.             P.D. 

Stars. 

Fields, 

Memorandums. 

H.   M.   S. 
o  55   10 

o  5^     4 

o  57  52 

0  59   10 

1  0  16 

D.  M. 

73  16 

74  0 
iM  17 

74  25 
74  1^ 

15 

3.8 

14 
11,1 

I 
I 

10 
I 

10 

^ 

I      I    10 
I      I    18 
I     2  52 
I     3  52 
I     4  15 

74     5 
III     0 

52     0 

IJ3   17 
94  52 

11,2 
5,2 

28,1 
2,8 

7'5 

10 
10 

10 

10 

10 

Very  clear  for  this  altitude. 
Moft  of  the  ftars  very  finall. 

I     4  33 

I     5  55 
I     7  27 

112     0 

I   12  48 

65  32 
7S  31 

45  23 
58  37 
60  19 

1 1,0 
9»2 
58 
20 

10 
10 

I 
I 
I 

I    13     4 
I    15  51 
I   iB  21 
I  23  21 
I  27  30 

94  50 
48  40 

48  40 
48  40 
65  42 

6.3 
30 
58 
44 
12,9 

10 

I 

I 

I 

10 

I   31  21 

I  32     4 

I  33  10 

I  33  32 

•    I  34  52 

87     7 

94  50 

100     8 

92  35 
60     8 

5,8 

7,3 

6,4 

7,1 
17 

10 
10 
10 

10 

I 

- 

I  43  30 
1  45  24 

I  48     4 

I  54  24 
I  58  55 

65  42 

69  43- 
100  12 

76  28 
61  55 

14,4 

7,1 

4,9 
12,1 

i5>o 

10 
10 

10 
10 
10 

2    4  28 
2    4  36 
2    7  12 
280 

2  10    4 

87    5 
78  38 

94  56 

83     3 

100  12 

6,4 

9,3 
7,8 

7,3 

4,3 

10 
10 
10 
10 

10 

R.A. 


Corjlru5ilon  cf  the  Heavens* 


22 


R.A. 

P.D. 

Stars. 

Fields. 

Memorandums. 

H.  M.   S. 

D.  M. 

2    II    30 

65  45 

14,8 

10 

2    16    27 

no  54 

4,2 

10 

^ 

2     19    27 

76  24 

9^9 

10 

2    22    17 

45  31 

82 

I 

2  23    6 

60  16 

14 

I 

2    23    19 

113     8 

4,2 

10 

^ 

2  24     6 

5«  30 

15 

I 

2    27    40 

1 15  21 

3'0 

10 

•^  The  fituationtoo  low  for  great  accu- 

2   30      0 

94  56 

6 

10 

racy. 

2    31    23 

76  22 

i3>8 

10 

2  35   14 

87     2 

5,6 

10 

2    38      0 

94  56 

6,6 

10 

:          2      42           7 

61  50 

14,8 

10 

2  47  32 

74     3 

II, I 

10 

Moll  of  the  ftars  exceedingly  fmall. 

2  49  22 

92  55 

9,0 

10 

2  49  30 

no  55 

6,1 

10 

# 

2  50     0 

94  56 

6,8 

10 

2  54  53 

76  22 

9,2 

10 

2  59  56 

81   10 

6,1 

10 

■ 

3     I  53 

78  37 

4,1 

10 

3     I  56 

81   10 

5.1 

10 

3    4  53 

78  37 

3,5 

10 

3  10  20 

lOO      2 

6,8 

10 

3  II     6 

59  29 

7'0 

5 

1  In  a  part  of  the  heavens  which  looks 

3  13    6 

59  29 

6,1 

10 

1       pretty   full  of  liars  to    the    naked 

3  15     6 

59  29 

9'4 

10 

J      eye. 

3  22  57 

83     I 

10,3 

10 

3  23  21 

92  49 

10,1 

10 

3  29  41 

46  35 

55 

I 

3  35    0 

62     I 

15 

I 

About  15  liars  generally  in  the  field. 

3  35  12 

100     3 

7.4 

10 

3  36     I 

113     3 

4,9 

10 

* 

3  42  49 

46  10 

54 

I 

3  48  16 

99  59 

8,1 

10 

3  55  II 

74     2 

11,0 

10 

1 

lvtA» 


224 


Mr,  Her  SO  H  EL  on  the 


R.A 

I'.D. 

Stars. 

Fields. 

Memorandums. 

H.  M.  S. 

D.  M. 

4     I   24 

92  48 

13,8 

10 

4    6   iB 

82  57 

i3'4 

10 

4    8  31 

114  55 

4>2 

10 

% 

4  12  41 

69  33 

i5»3 

10 

And    many    more,     extremely    fmall, 

4  16  34. 

111  45 

6,2 

10 

•^      fufpefted. 

4  26  34 

112  45 

8,8 

lO 

■5f 

4  27   II 

70  41 

25 

I 

4  28  41 

70     I 

17 

I 

4  29     5 

69  24 

30 

I 

4  30  H 

99  50 

9'7 

10 

4  31   ^9 

67  33 

i5»6 

10 

4  32  29 

6()     2 

36 

I 

4  33  31 

114  55 

8,1 

10 

■)(■ 

4  42  14 

86  27 

19,9 

10 

4  S3  22 

72  59 

56 

I 

4  57  45  ' 

83  22 

38 

I 

4  58  45 

84  36 

35 

I 

5     I   16 

69  23 

34 

I 

S     3  45 

83  29 

17.7 

6 

5  10  52 

69  22 

74 

I 

5  II  22 

96  37 

24 

I 

5  17  22 

96  15 

8,9 

8 

5  18    0 

80  46 

30 

I 

About   30  ftars   in  the  field,  not  very 

5  21     7 

92  52 

i9»i 

10 

exadly  gaged. 

5  24  12 

66     5 

36 

I 

5  27     3 

68  52 

58 

I 

5  27  48 

no  40 

17.7 

10 

# 

5  33    4 

76  10 

65 

1 

5  33  12 

66  26 

86 

I 

5  33  17 

iH  59 

i3'5 

lO 

^ 

5  34  45 

70  33 

50 

I 

5  36  30 

62     I 

20 — 30 

From  20  to  30  ftars  in  the  fields,  not 

5  37     4 

74  26 

140 

i 

very  exactly  gaged. 

5  38  45 

70     8 

73 

I 

5  41   12 

66  43 

60 

I 

i\.*ifi.* 


ConJlruBion  of  the  Heave?is, 


225 


R.A. 

P.D. 

Stars. 

Fields. 

Memorandums. 

H.  M.  S. 

D    M. 

5  44     0 

n6  43 

11,5 

10 

^ 

5  45  3^^ 

83  30 

50 

5  47  34 

112  34 

^9'3 

10 

^ 

5  48  30 

62     I 

30 

About  30  liars  in  the  field ;   not  very 

5  48  44 

92  51 

22,4 



CKadlly  gaged. 

5  49     0 

80     5 

50 

' 

5  52   14 

Q3  14 

44 

5  5^  30 

83  30 

60 

S  S3     "^ 

80     5 

no 

5  55     4 

92  56 

57 

5  56  40 

70  27 

73 

5  57     0 

80     5 

60 

5  57  37 

1 10  33 

19,6 

10 

# 

5  58  51 

88  36 

90 

5  59  30 

83  30 

80 

I 

6     0  23 

86  38 

24,1 

10 

6     r     0 

80     5 

70 

. 

640 

80     5 

90 

654 

67  17 

120 

4 

Very  unequally  fcattered. 

6     b  14 

96  16 

52 

6     6  30 

83  30 

80 

6     6  30 

80     5 

70 

< 

6     6  38 

91  45 

54 

Like  the  rell:,  or  many  fuch  fields. 

6     6  40 

68  24 

56 

690 

80     5 

74 

^ 

6     9  34 

113  35 

26 

# 

6   II     0 

62     I 

30—40 

Between. 

6  II     0 

80     5 

63 

The  lead:  number  of  ftars  in  the  field  I 

6  II  34 

H2     5 

2>Z 

%    could  find  in  this  neighbourhood. 

6   II  37 

90  15 

About  60  or  70  generally. 

6   14.    4 

68   II 

178 

6  14  38 

90  15 

77 

6  17  45 

62     I 

50 

6  18   14 

96  12 

38 

Very  unequally  fcattered. 

6  19  14 

93  59      72 

VcL.  LXXV. 


S 


IvtAi 


^"6 


il<fr.  Herschel  on  the 


R.A. 

1 

F,D. 

Siars. 

Fields. 

Memorandums, 

H.  M.   S. 

D.    M. 

6  26   17 

iH  59 

15.9 

10 

6    27    14 

94  3^ 

132 

2 

* 

6   27   32 

70  23 

5^ 

6  3-1  48 

115  40 

40 

^   34-  44 

9^  25 

94 

6  34  55 

79     5 

50 

Generally  about  50  ftars. 

6   56     0 

94  5^^ 

62 

Twilight. 

6  37   ^5 

75     5 

70 

Geaerally  about  70  flars. 

6  39     8 

99     7 

50 

* 

0  40     0 

116  43 

31.3 

10 

6  43  25 

79     5 

67 

6  44  28 

IGO    30 

^7 

# 

6  49     5 

87     21 

120 

^ 

6  49  30 

77   3^ 

S^ 

Many  fields  like  this. 

6  49  44 

9^   'iZ. 

iiO 

« 

6  51     8 

98  33 

78 

^ 

6   52     0 

116  21 

4.8 

!    ^  52  ^5 

79     5 

60 

A,bou:  60  ft.irs. 

6  52  44 

9-  59 

98 

1 

6  54     9 

111    11 

45 

vf 

6  57     8 

J  00     I 

34 

# 

6   57  3S 

9b  50 

^^ 

!% 

6  58  39 

112  48 

81 

% 

7     0  25 

79     5 

70 

7     4    0 

92     3 

102 

^ 

7     4  38 

98  59 

70 

■^ 

7     5     9 

III   II 

70 

■^ 

7     S.    9 

112   15 

b2 

:Sf 

7   12     8 

100     5. 

iiS 

:)f 

7   15  3S 

98  12 

112 

:Jf 

7   19    0 

91  51 

53 

^ 

7  20    0 

78  59 

48 

7  25     9 

III  21 

168 

#  One  of  the  richeft  fields. 

7  28     9 

112  34 

2C4. 

g 

7f  A  field  like  the  reft. 

7  3^     3 

115  28 

86 

i\i..>.  i* 


ConfrnSlbn  of  the  Ueavms* 


227 


R.A. 

P.D. 

Stars. 

Fields. 

Memorandums. 

H.  xM.  S. 

D.  iM. 

i 

7  41  9 

1 13  26 

loS 

^-                       i 

7  53  4 

80  39 

28,3 

10 

# 

8  I  4 

III  15 

yo 

■^ 

8  3  4 

113  31 

66 

8  b   3« 

ICO  5 

43 



\ 

8  7  3^ 

99  3 

45 

* 

b  II  8 

99  25 

2  4.,  2 

10 

% 

8  12  34 

I J2  ii; 

52 

:Jf 

8  22  4 

J 11  30 

35 

^ 

8  31  4 

112   I 

^l 

8  32  24 

1 12  7 

30 

8  35  4 

112  17 

24 

8  35  14 

III  19 

20 

8  40  4 

III  II 

22 

:^ 

8  45  4 

113  22 

13 

8  46  39 

91  26 

20,3 

10 

% 

8  48  4 

112  23 

16,2 

10 

8  57  25 

66  20 

8,3 

10 

^ 

9  5  38 

91  22 

13,8 

10 

% 

9  10  4 

115  17 

14,0 

10 

9  20  4 

112  23 

15.8 

10 

9  20  40 

99  12 

II, I 

10 

9  20  58 

88  7 

11.5 

10 

^ 

9  35  4 

1 12  23 

13,0 

10 

9  38  4 

115  17 

10,1 

10 

9  38  8 

90  23 

7'9 

10 

^ 

9  42  16 

86  16 

7,7 

10 

#                       ,^ 

9  45  49 

112  21 

13' 2 

10 

Strong  twilight. 

10  0  4 

1^5  17 

■9,1 

10 

10  16  8 

88  8 

7'2 

10 

# 

10  19  32 

91  14. 

6,5 

10 

10  25  8 

b8  8 

4,9 

10 

# 

10  26  0 

81  41 

5,6 

7 

^ 

II  4  4 

81  38 

s-,z 

6 

:)f 

II  7  36 

91  14 

5-6 

10 

G  ^ 


R,A. 


28 


Mr.  Herschel  on  the 


RA. 

P.D. 

Sr;u-s. 

l""lflt'S. 

Memorandums. 

H.  M.  S. 

D.   M. 

- 

1 1    1  o     6 

115  23 

6,5 

10 

Twilight, 

II    i6  52 

81   38 

8 

■H- 

II    .0  37 

91    17 

4.9 

10 

, 

II   53  43 

81  3'. 

6,0 

5 

^ 

12     5     6 

78  57 

2,2 

13 

% 

12  30  40 

79     3 

3'4 

II 

% 

' 

12  46  51 

81  40 

4,6 

13 

^ 

12  4b   19 

79     4 

3>9 

13 

^ 

1 

12  53  45 

loi  45 

9'3 

10 

Twilight. 

i 

12  57     8 

99  5^ 

8,1 

10 

Pretty  itrong  day-light. 

i 

13     I   19 

79     4 

3,8 

12 

H- 

• 

13  17  27 

101  45 

8,6 

10 

Twili;:;ht. 

13  22  49 

ICO       I 

8,4 

10 

Some  day-light. 

13  27  57 

loi  45 

11,3 

10 

13    31     lO 

75  55 

5-6 

I 

^f  Generally  about  5  or  6  ftars  in 

the  field. 

13  38  53 

104  27 

8,5 

10 

13  48  49 

100     I 

9,2 

10 

Strong  twilight. 

13  51   27 

101  45 

10,0 

10 

13  55  44 

58   II 

7,4 

lO 

■)f  Twilight. 

13  57  53 

104  27 

12,3 

10 

Moft  very  fmall. 

-  14     9  49 

100     I 

11,2 

10 

Twilight. 

14  13  52 

113     4 

9i7 

10 

14  14  57 

lOI    45 

8,8 

10 

14  24  49 

81  53 

2,7 

6 

14  29  45 

100     5 

^3^3 
8,8 

10 
10 

14  30     7 

66     3 

■^  All  fizes. 

14  30     8 

80  38 

3'5 

13 

14  33  22 

58     7 

8,9 

10 

%  Chiefly  fmall. 

14  33  52 

113     4 

10,3 

10 

14  39  57 

lOl   45 

14,0 

10 

All  fizes. 

14  40  36 

64  47 

6,4 

10 

14  44  II 

114  54 

10,3 

10, 

14  49  52 

113     4 

12,8 

10 

H  51    H 

58   10 

9,2 

10 

%  Twilight. 

H  52   58 

60  41 

4,4 

10 

9f  Strong  Aurora^borealis, 

— - 

R.A- 


Conjlruti'ion  bf  the  Heavens, 


Zig 


R.A. 

r.D. 

Stars. 

Fields. 

.\]emor.in(iiinis. 

H.  iM.  S. 

D.  M 



H  53     7 

65  }5 

9.0 

10 

Chiefly  lar<:^e. 

'4  SS  36 

64  47 

6,6 

10 

Moil  very  Imall, 

'4  59   11 

114  54 

b,8 

lO 

15     2  42 

62  48 

8,3 

10 

15     3     7 

66   15 

9v5 

]0 

^5    4  36 

64  47 

5,0 

10 

1 

15     8  37 

113     0 

14,1 

10 

^5     8  45 

93     5 

9'4 

12 

Very  fmal!. 

15   13  \~ 

62  48 

8,9 

10 

15   J5  44 

58   17 

10,0 

10 

7f  Twilight, 

15   19  48 

60  40 

4.9 

10 

9f  Strong  Aurora  boreaiis,  fo  as 

to  aftcd 

15  20     0 

75  52 

9,5 

4 

the  gages. 

15.  21     0 

93     5 

10,9 

12 

15  26     7 

^^  SI 

11,0 

5 

IS  28  48 

99  51 

»3'i 

10 

15  29     7 

66  15 

10,6 

10 

All  fizes. 

15  29  44 

58  17 

8,9 

10 

■^  Twilight. 

15  32     0 

75  51 

6 

6 

15  33  52 

III  32 

12,8 

10 

15  35    0 

75  51 

6,5 

6 

15  42     2 

58  14 

^3'! 

10 

^  Twilight, 

15  42     3 

116  56 

18,6 

10 

15  42  sz 

^^3  47 

32,5 

2 

The  ffcars  too  fmall  for  the  gage, 

p 

15  46  30 

93     5 

10,8 

12 

15  48  37 

113    0 

17,1 

10 

'        * 

15  48  46 

63     4 

12,4 

JO 

15  49  52 

111  32 

18,1 

10 

The   fitxiation  fo  low   that  it 

requires 

15  50  20 

114  55 

9,2 

10 

attention  to  fee  the  liars. 

15  57     3 

116    q6 

10 

16     0     2 

58    14 

12,2 

10 

■^  Twilight. 

160     c; 

116   56 

6,1 

lO 

16     0  12 

214  57 

1,6 

10 

16     3  12 

114  57 

2,0 

10 

16     4    0 

75  43 

13 

6 

All  fizes. 

16     4  19 

1 13     6 

'5 

10 

Perfeaiy  clear.     See  p.  256. 

iv»A, 


2p 


Mr,  PlEnsciiEL  on  the 


R.A. 

P.D. 

Stars. 

Fields. 

Memor'.indums. 

H.  M.   S. 

D.  M. 

1 6     4  46 

63     4 

12,0 

10 

Moll:  iVnall. 

16     4  52 

99  57 

14,6 

10 

Moon  and  twilight. 

16     6   28 

113     4 

,7 

10 

Pcrfedly  clenr. 

16     712 

6(^   15 

i3>3 

10 

16     8     6 

ii5      1 

3,8 

6 

16     8   II 

93     9 

12,2 

12 

16     8   16 

116  48 

1 1,6 

10 

16     9  28 

^^3     4 

1,1 

10 

Perfeftly  clear.      See  p.  256. 

16   II   28 

113     4 

1.4- 

10 

The  iaaie. 

16  13  28 

113     4 

1,8 

10 

g  Serpentarii   and  19   Scorpii 

vifible  to 

16  1.3  52 

58  24 

14,2 

10 

#  Moil:  fniall.                     [the 

naked  eye. 

16   14  42 

t>3     7 

155I 

10 

Moll  vervfmali. 

16   15  37 

80  40 

9'7 

12 

All  fizes. 

16  17  28 

"3     4 

4,7 

10 

16  20  51 

81  57 

13,8 

6 

16  23     0 

73  43 

24 

I 

16  23  28 

"3     4 

13,6 

10 

16  24  II 

93     9 

i3'6 

12 

Require  attention  to  be  feen. 

16  25     7 

bo  40 

14.6 

li 

16  27  32 

68  23 

21,6 

10 

Twilicrht. 

0 

16  29  16 

116  48 

50,4 

10 

16  30  31 

80  4.0 

34 

I 

16  31   12 

66   15 

18,4 

10 

Strong  twilight. 

16  32  28 

113     4 

20,3 

10 

Moft extremely  fmall. 

16  32  52 

58   24 

i5»^ 

10 

■^  Moll  fmall. 

16  35  42 

63     7 

16,5 

10 

^ 

16  35  48 

93   15 

18,6 

12 

All  fizes. 

16  38  12 

66   15 

20,1 

10 

Strong  twilight. 

16  38  45 

107  57 

i9'9 

10 

Strong  twilight. 

16  40  51 

113   14 

41,1 

8 

16  45  32 

68  23 

i9'0 

4 

Hazy. 

16  51  45 

107  57 

29,8 

10 

16  52  22 

66  26 

16,6 

10 

Day-light  pretty  flrong. 

16  55  42 

63     7 

26,6 

10 

-jf  Strong  twilight. 

17     I   34 

58   11 

18,8 

10 

•9f    Strong  day  light. 

T:  "v 


R.A. 


1". 


Cofijlriiclion  of  the  Heave /ts. 


231 


R.A. 

P.D. 

Stiirf. 

Fit  Ids 

Memorandums. 

H.   M.  S. 

D.  M. 

17     3  22 

66  26 

35 

f 

■X-  Day-]ig!it  too  ilrcng  for  gaging. 

17     6   3(3 

98  38 

i3>7 

10 

Moft;  finall,  a;id  more  lulpected. 

17     9  30 

11^  SS 

7,6 

10 

^'7     9  32 

68  23 

32'3 

10 

17    11    10 

66  26 

3« 

1 

■^  D.-3j/-tight  pretty  flrong. 

17   13  24 

63  21 

32,8 

10 

■)(-  Strong  day-light. 

17   17   3b 

III   47 

15,3 

10 

Moon  and  day-lighc. 

17  25     7 

108     s 

23 

10 

17  27   29 

lib  48 

25 

I 

17  28  32 

68  23 

42,2 

5 

I 

■^  Twilight. 

17  30  29 

116  48 

42 

17  33  29 

1 16  48 

52 

I 

Day-light  very  ftrong. 

17  34  36 

98  38 

18,5 

10 

Very  ftrong  twilight. 

17  39  3+ 

120     0 

84 

I 

Moft  large. 

17  40  41 

114  52 

77 

I 

Day-light  very  ftrong. 

17  41  29 

116  48 

82 

I 

Day-light  very  ftrong. 

17  43  45 

105     3 

80 

I 

Flying  clouds. 

17  48     0 

61    18 

25,6 

5 

Moft  large. 

17  50     4 

56   16 

27,2 

10 

Twilight. 

17  50     7 

108     5 

59 

I 

Like  the  reft  in  this  part  of  the  heaven. 

17  52     7 

108     5 

118 

I 

Many  fuch  fields  juft  by. 

17  52  17 

98  43 

7,6 

10 

.  17  52  30 

62   12 

40 

I 

Moft  large. 

17  52  32 

68  19 

54 

I 

■X-  Strong  day-light. 

17  55     7 

108     5 

232 

I 
2 

17  55   15 

106     6 

112 

I 

Many  fuch  fields. 

17  55  3« 

112  54 

1 12 

I 
2 

17  57  30 

60  28 

38 

I 

Moft  large. 

17  58  37 

103  24 

35 

I 

17  58  41 

118  57 

64 

I 
I 

17  58  49 

122  17 

17 

17  59     I 

108     8 

320 

i 
2 

^7  59  19 

104  24 

68 

I 

18     0  13 

122   1 1 

27 

I 

18     3  49 

120  42 

19 

I 

JKo  A» 


*>^  \f*i 


5- 


Mr.  Herschel  on  the 


R.A. 

P.D. 

Stars. 

t-ields. 

Memorandums. 

H.  xM.  S 
i8     5   17 
18     6  37 

18     7     4 
18     7     4 

18     7  37 

D.  M. 
98  47 
go  36 
62    14 
56    16 
10^   25 

65 

9'4 

40 

38,2 
88,0 

I 

10 

I 
5 
3 

Too  fbon  for  gaging,  not  having  been 
MoC;  large.                    J  long  enough  out 

lin  the  dark. 

18   10     7 
18  10  52 

!    18    II    49 
18    13    37 
18    13    52 

120  58 
61     8 

104     6 
104  16 

93  " 

20 

78 
170 
238 
2,0 

I 
1 

r 
2. 

7 

Chiefly  large. 

18    14   46 
18    15    28 

18   i6  52 
18  18  40 
18   19  37 

56  20 
92  42 
92  42 
92  42 

102  34 

48 

3.4 

8,9 
13,8 

9^5 

I 

7 
7 
7 
2 

18  20     7 
18  20  46 

18    21        I 
18    21     12 
18    21    31 

103  18 
92  42 

103  55 
90  41 

103  36 

19 
25,8 
22 
8,6 

24 

6 
10 

18    22       4 
18    22       4 
18    22    19 
18    22    37 
18    24       3 

62     7 

56   16 
1 04     6 

lOj  45 
115   10 

48 

39.6 

14 

30 

35 

3S 

30 

88 

25 
39 

Large  and  fmall. 

18    24      4 
18    24       7 
18    24    10 
18    24   43 
18    25    37 

109  35 

102  31 

92  59 

103  39 
102  34 



Twilight. 

18    26    17 

18    26    25 
18    26    47 
18    27       I 

'8  27  55 

98     3 

103  57 

97  43 
120  58 

120  44 

\  1 1 

60 

250 

30 
32 

1 

R.A. 


Conftrudlion  of  the  He  an)  em. 


22 


^Z 


R.A. 

P.D. 

Stars. 

Fields. 

Memor.  ndums. 

H.  M.  S 

D.  M. 

i8  28     7 
18  28     8 
18  28  25 

102  51 
91   44 

103  9 

^3 

39 

20 

I 
I 
I 

Extremely  fnnall. 
Moll:  Iniall. 
Extremely  fmall. 

18  28  37 
18  29  25 

122  25 

103  24 

12 

20 

I 
I 

Extremely  fmall. 

18  29  47 
18  29  49 
18  30  34 
18  31   10 
18  31    10 

97  50 
121  39 

57  18 

92  42 

108  53 

'50 

24 

62 

i3»7 
74 

I 

I 
I     ' 

7 

I 

Tvvilieht. 

18  31    13 
18  31   17 
18  31   34 

103  19 

97  53 
62  34 

112 
188 

76 

I 

I 
2 

I 

All  fizes. 

Many  more  fnfpe6led. 
#  Large  and  Imall. 

18  31  49 

18  r,  4 

121  39 

108  43 

19.3 

88 

10 

I 

Twilight. 

i 

18  33    7 
18  34   5 
18  34  47 
18  34  58 

18  36  34 

103  53 

98  34 

71  53 

60  41 

1 10  12 

146 

130 

78 

So 

83 

I 
2 

I 
I 
I 
I 

■Jf 

Large  and  fmaU. 
Twilight. 

18  36  34 
18  36  47 
18  37  34 
18  38    I 
18  39  40 

91  37 

72  28 

93  29 

104  14 

93  52 

176 

224 

5 

118 

116 

I 

4- 

I 
2 

: 

2 
I 

^ 

18  40  28 
18  40  47 

18    41    22 
18   42    49 
18    43    17 

92  47 

71  48 

91   37 
121  39 

72  8 

10 

236 
156 
15,2 
368 

I 

I 
4 

4- 
10 

4 

Very  clear  for  this  altitude. 

- 

18  43  33 

18  44  34 
j8  44  34 
18  47  32 
18  48     4 

1 19  21 

112  43 

60  34 

91   14 

1 10  12 

21 

^Z 

84 
328 

83 

I 
I 

I 

I 
4 

All  fizes. 

VcL.  L 

XXV. 

Hh 

R.A. 

254 


Mf\  Herschel  on  the 


R.A. 

P.D. 

Stars. 

Fields. 

Memorandums.                           1 

H.  M.  S. 

D.  M. 

1 8  50  16 

60  55 

136 

I 
2 

Many  of  them  fmall. 

18  51     4 

57  20 

84 

I 

1 

1 

18  51   32 

10^6  26 

3^,8 

5      . 

Strong  twilight. 

18  52  49 

115  30 

2^,2 

5 

18  54     4 

57   18 

93 

I 

iS  54     8 

91    14 

328 

4- 

18  54  55 

104  23 

180 

I 

18  55     4 

108  41 

80 

I 

18  55   16 

62  31 

206 

i 
-> 

18  59     8 

91    14 

328 

I 

4- 

18  59  26 

72  37 

40 

I 

Too  looa  for  gaging. 

19     I     2 

71  40 

75 

I 

19     I   34 

56  47 

127 

I 

Moonlight. 

19     2  29 

74  53 

204 

I 
4 

^  Twilight. 

19     2  37 

103   16 

160 

I 
2 

19     2  49 

121   39 

14,1 

10 

19     3  34 

55  56 

14b 

-> 

D 

19     6  34 

61     8 

196 

I 

2 

And  manv  fmall  befides. 

19     7  34 

56  56 

130 

I 
2 

D 

19     7  52 

57  59 

116 

I 
2 

19     8  38 

92     8 

120 

T 
2 

19     9  37 

109     I 

60 

1 

19     9  40 

5(5  51 

130 

I 

D 

19  12  59 

75  21 

58 

I 

^ 

19  13  50 

59  59 

256 

I 
4- 

19  »3  52 

59  29 

158 

I 
2 

19  14     2 

72   15 

60 

I 

^ 

19   14    4 

61   21 

279 

I 
3 

Too  crowded  for  accuracy. 

19  H  55 

103  36 

64 

I 

Changeable  focus^ 

19  15  40 

55  26 

160 

I 

D   bright. 

19  16  50 

60  43 

.96 

1 
4- 

19  16  59 

7S  23 

5^ 

I 

•^ 

19  17  44 

108  12 

50 

1 

19   18  2^ 

78     9 

196 

I 

4- 

^ 

19  18  28 

61  21 

279 

I 

R,A>. 


I 

^oPjirUi 

jtion  oj 

IDS  neavens,                       23  j 

R.A. 

IM). 

Stars. 

Fields. 

1                       Memorandums. 

1 

H.  M.  S. 
19   19  52 
19   19  55 
19  20  51 
19  21      I 
19  21   34 

D.  M. 

57   t4 

108    J2 

<>o  55 

78  47 
55  ^7 

180 

55 

3^4 

472 
208 

t 

I 
I 
4 
1 
4- 
r 
2 

1)   bright. 

19  22  27 
19  24  36 

19  24  49 
19  24  50 

19  24  53 

62  29 

56  49 

104  24 
60  43 

"3  51 

320 
224 

3^ 
296 

18,3 

i 

T 
A- 

I 
I 
4- 

10 

Ciiangeable  focus. 

19  25     4 
19  25  16 
19  25  22 
19  25  -^■] 
19  27  36 

57     9 
64  18 

59  36 
^03  50 

72  34 

190 

280 
340 

55 
424 

r 
2 
I 

I 

4 

I      1 

I 
4 

D   bright. 

Changeable  focus. 
•^  Toofmall  and  too  crowded  to  be  cer- 

19  27  44 
19  28     I 
19  28     6 
19  28  52 
19  28  52 

61     8 

103  30 

55  49 

59  26 

5^  47 

240 

45 
288 

344 
186 

T 

I 
I 

f 

1 

2 

[tain  of  the  number. 
Changeable  focus. 

])  very  bright. 

19  29  46 
19  30  36 
19  30  36 

19  3^  33 
19  32     9 

65  10 

74  33 

54  53 

92  34 

109  44 

34 
588 

312 

62,2 

23,8 

I 

I 
4- 
I 
4 

5 

10 

Mr 

19  32  15 

19  33    4 

19  33     7 

19  33  14 
19  33  20 

62  3S 

55  34 

103  12 

61     8 
5B  59 

296 
212 

50 

240 

232 

I 
4 
I 
2 

I 

I 
3 
I 
4 

" *      ' 

r 
J 

> 

Changeable  focus. 

19  34  51 

19  35  34 
19  36     6 

19  36  37 
19  36  50 

"5  44 
63   19 

54  57 
102  31 

60  35 

14,1 
256 

384 

68 

296 

10 

I 

4 
I 

4 

I 

I 
4 

Changeable  focus. 

Hh 


K.»A 


■7  -^n 


Mr.  Herschel  o?2  the 


R.A. 

P.D. 

Stars. 

Fields, 

Memorandums. 

H.  M.   S. 

D.  M. 

1 

19  40  33 

63     0 

2q6 

I 

4 

19  40  46 

59   ^2 

192 

1 

4- 

19  40  48 

74  33 

^88 

1 
4 

"^ 

19  42  33 

73   H 

352 

I 

4- 

# 

19  43  30 

57  23 

130 

I 

2 

D 

19  43  56 

64  27 

124 

I 
2 

Molt  lar^e. 

19  45  36 

77  5^ 

140 

I 
2 

^  Fault    li  . 

'^9  45  37 

103     3 

50 

1 

19  46  21 

73  14 

^52 

I 

4 

^ 

19  46  51 

115  44 

12,8 

10 

Strong  twilight. 

....               .  .  1 

19  47     8 

^0  3S 

312 

1 

4 

19  47   18 

109  46 

20,9 

10 

' 

19  47  22 

57  38 

312 

1 

4 

Very  unequally  fcattcred,. 

19  49     6 

57   13 

268 

J 
4 

19  49  48 

56  51 

120 

I 
2 

D 

19  SO     5 

92  39 

39.2 

5 

%  Moft  fmall. 

19  51   37 

62  37 

51 

I 

'    19  5^     0 

57   15 

220 

I 
2 

D 

19  53     I 

60  35 

80 

I 

19  53  28 

63  40 

52 

I 
2 

19  53  40 

54  59 

306 

I 

4 

19  53  49 

121   39 

7J 

10 

i    19  54    0 

55   12 

160 

I 
2 

5 

19  54  12 

78     3 

120 

I 
2 

•^  Faint  D  . 

19    54    22 

59  58 

136 

I 
4 

19  55     7 

62  41 

48 

I 

19  56  19 

60  44 

112 

T 

2 

19  56  22 

57   17 

192 

1 
4 

^9  57   19 

62  34 

45 

I 

19  57  40 

58  29 

104 

I 
2 

19  59  49 

62  37 

41 

I 

20    0  21 

79     3 

S^ 

I 

9f  Strong   ])  .. 

20    0  24 

55  12 

184 

I 
2 

5 

20     0  25 

<^o  33 

80 

I 

Moft  of  the  ftars  extremely  fmall. 

20    051 

ijc;  44 

12,2 

10 

Twilight. 

J^oXA* 


Conjlriidllon  of  the  Hea'-oens, 


R.A, 

P.D. 

Stars. 

Fields. 

Memorandums. 

H.  M.    S. 

D.   INI. 

20     I   39 

79  34 

68 

I 

■^  Strong  D  . 

20     5   26 

56  34 

46 

I 

1) 

20     5  27 

72  56 

2S0 

T 

_ 

20     6  23 

J07  27 

22,6 

10 

20     6  43 

62  32 

75 

I 

Many  fmall. 

20    8  26 

56  27 

^7»4 

5 

]) 

20     8  27 

72  56 

280 

I 

4 

20     8  58 

103  37 

3« 

I 

20     9     6 

log  40 

24,2 

5 

20     9  52 

102  48 

3' 

I 

20  12  22 

58    14 

76 

1 

20  17  20 

76    12 

184 

1 

4 

Some  t\viIio;ht. 

0 

20  1 8  51 

1^5  44 

10,6 

10 

Twilight. 

20  20  58 

61   27 

88 

I 

20  21   36 

71   28 

104 

1 
2 

Hazy. 

20  22  56 

56  27 

66 

I 

D 

20  22  58 

103  26 

20 

I 

20  24  51 

115  44 

9o 

10 

T-^rllight. 

20  25  58 

103  26 

22,8 

10 

Changeable  focus. 

20  25  59 

07   27 

248 

J 

A' 

5 

20  26     I 

92  44 

30,8 

"^ 

20  26  46 

109  37 

16,7 

10 

Not  clear. 

20  26  49 

121   39 

7'7 

10 

A  little  hazy. 

20  27  33 

96     7 

39 

I 

Moil  fmall. 

20  34  51 

115  44 

9'5 

10 

5 

20  35  53 

61   20 

142 

I 
2 

20  37   1 8 

58  28 

loS 

I 
2 

20  37  34 

97     6 

26,6 

10 

% 

20  38     I 

92  44 

28,2 

5 

% 

20  39  42 

66  37 

78 

r 
2 

20  40  22 

56  21 

192 

I 

4 

, 20  41   II 

67  54 

105 

I 
2 

20  41  56 

74  33 

116 

I 

20  42  59 

62   14 

112 

I 
-1 

1  20  43     I 

70  29 

76 

I 

Sk,aAx 


23 


3 


Mr,  Herschel  on  the 


R.A. 

P.D. 

Stars. 

Fields. 

Memorandums.                           \ 

H.  M.   S. 

D.    M. 

20  43  30 

54  47 

260 

I 

4- 

Moil  of  the  ftars  of  the  fame  fize. 

20  44  59 

70     6 

80 

I 

20  47   13 

60  46 

120 

I 
2 

20  49     I 

92  44 

27,0 

5 

# 

20  49  10 

57   II 

248 

I 

4- 

* 

Mofl  of  a  fize. 

20  50  59 

10-^    26 

I7>2 

3 

20  51   23 

68  30 

70 

I 

20  53  29 

103  26 

17,4 

5 

20  54     1 

107  47 

10,3 

10 

20  56  59 

103  26 

14,9 

10 

Moil:  extremely  fmall. 

20  57  55 

61  25 

64 

I 

Twilight, 

20  59     I 

92  44 

21,4 

5 

^ 

21     I     6 

96  43 

40 

I 

^  Moft  fmall. 

21     3  29 

66  39 

80 

T 
2 

21     3  53 

73     9 

55 

I 

21     6  13 

69  23 

40 

I 

A  little  hazv. 

21     6  55 

103  32 

II, I 

10 

21     7  49 

109  45 

12,8 

10 

21     7  59 

64  58 

no 

r 

21     9  25 

61  36 

75 

I 

Strong  twilight. 

21   10  13 

60  39 

70 

I 

Strong  twilight. 

21   II   17 

73  18 

50 

I 

21   II  42 

96  13 

25 

I 

:)f 

21    12     I 

92  44 

16,4 

5 

21   IS     3 

109  56 

15.3 

10 

21  16  43 

59     7 

76 

I 

21   18  54 

57  20 

50 

I 

21  20  18 

96  43 

24 

I 

* 

21  21     0 

107  49 

8,1 

10 

21  22  14 

76  33 

3°'° 

5 

21  25  31 

92  44 

8,0 

5 

^ 

21  29  12 

83  II 

21,6 

5 

21  30  58 

78  57 

18,9 

10 

21  32  10 

57   H 

25 

I 

1  21  33     I 

92  44 

15.4 

5 

Strong  txvilight. 

R.A, 


ConJiruBion  of  the  Heavens. 


22 


39 


R.A. 

P.D. 

Stars.  Fields. 

Memorandums. 

H.  M.  S. 

D.  M. 

21  34  55 

97  17 

I3'6 

10 

^ 

21  36  38 

65  55 

42 

1 

21  38  20 

65  38 

60 

I 

21  39  55 

96  17 

18 

I 

■^ 

21  41  52 

58  42 

44 

I 

21  43  22 

109  5S 

J^5 

10 

^ 

21  45  4 

59  39 

52 

I 

21  48  22 

59  30 

29 

I 

21  51  52 

58  5& 

61 

I 

21  51  55 

97  17 

II. 5 

10 

21  54  22 

109  55 

12,8 

10 

^- 

21  57  49 

59  37 

60 

I 
2 

- 

21  5§  4 

75  7 

33 

I 

21  58  19 

59  6 

40 

1 
2. 

21  58  43 

58  34 

32,6 

5 

D 

21  58  49 

58  20 

34 

I 

22  2  25 

60  9 

42,6 

5 

22  2  52 

109  55 

7,4 

10 

^ 

22  3  56 

71  48 

25,1 

10 

22  7  22 

109  55 

8,9 

10 

:Jf 

22  10  28 

75  2 

26 

I 

22  II  32 

97  H 

10,7 

10 

-}f  Twilight. 

22  II  35 

65  48 

26,6 

5 

22  18  32 

97  H 

9,1 

10 

if.    Twilight. 

22  20  35 

109  58 

8,3 

10 

•>f 

22  20  55 

78  54 

11,7 

10 

Blight  ])  . 

22  27  41 

95  4 

8,1 

10 

22  30  35 

109  58 

5'0 

10 

i(- 

22  31  28 

73  59 

17,3 

10 

22  33  6 

76  52 

16,5, 

10 

22  34  40 

61  56 

20,1 

10 

22  35  35 

109  58 

7' I 

10 

^ 

22  36  49 

71  57 

18,5 

10 

22  39  41 
22  40  5 

82  5 

19 

I 

65  48 

21,3 

10 

K.>As 


240 


Mr,  Herschel  on  the 


R.A. 

P.D. 

Stars. 

Fk^1c:s. 

Memorandunis. 

H.  M.  S. 

D,  M. 

22  43  SS 

60  9 

26,7 

10 

Faiat  J 

22  45  3 

80  47 

13,2 

10 

2  2  45  30 

58  38 

17,2 

10 

5 

22  48  49 

71  57 

13.4 

lO 

22  52   9 

78  43 

8,2 

10 

I> 

22  52  41 

95  4 

8,9 

10 

22  55  40 

7i  54 

11,6 

10 

22  56  55 

67  53 

12,1 

10 

22  58  19 

78  42 

9,2 

10 

D 

23   0  27 

113  12 

4,4 

10 

23   0  30 

58  38 

18,7 

10 

> 

23   2  59 

65  50 

21,3 

10 

23   5  35 

109  58 

7'3 

10 

D 

23   8  52 

95  I 

7,5 

10 

Mofl  extremely  fmall. 

23  10   4 

^4  SS 

26 

1 

23  II  40 

61  48 

21,1 

10 

23  12  40 

71  54 

11,9 

JO 

23  17  50 

81  0 

9,7 

10 

23  23  5S 

69  48 

12,1 

10 

23  25  32 

113  12 

3' I 

10 

% 

23  32   2 

69  Si 

9,5 

10 

23  33  20 

79  45 

10 

1 

23  43  2 

69  51 

10,9 

10 

I 

23  44  47 

45  24 

50 

I 

23  46  52 

113  17 

4,2 

10 

^ 

23  46  55 

65  36 

15,3 

10 

^ 

23  59  21 

87  10 

5,t> 

10 

123  59  56 

95  4 

7,8 

10 

P  R  O- 


ConJlruBlon  of  the  Heavens*  241 


PROBLEM. 

Thejiars  being  fuppofed  to  he  nearly  equally  fcaitercd^  and  their 
number,  in  a  field  oj  view  of  a  known  angular  diameter ^  being 
given,  to  determine  the  length  of  the  vfual  ^ay. 

Here,  the  arrangement  of  the  flars  not  being  fixed  upon,  we 
muft  endeavour  to  find  which  way  they  may  be  pLiced  io  as  to 
fill  a  given  fpace  moft  equally.  Suppofe  a  redangular  cone 
cut  Into  fruftula  by  many  equidiftant  planes  perpendicular  to 
the  axis  ;  then,  if  one  fliar  be  placed  at  the  vertex,  and  another 
in  the  axis  at  the  firft  interfedion,  fix  ftars  may  be  fet  around  it 
fo  as  to  be  equally  diftant  from  one  another  and  from  the  cen- 
tral ftar.  Thefe  pofitions  being  carried  on  in  the  fame  manner, 
we  fiiall  have  every  ftar  within  the  cone  furrounded  by  eight 
others,  at  an  equal  diflance  from  that  ftar  taken  as  a  center. 
Fig.  I.  (tab.  VIII.)  contains  four  fedions  of  fuch  a  cone  diftin- 
guilhed  by  alternate  (hades,  which  will  be  fufficient  to  explain 
what  fort  of  arrangement  I  would  point  out. 

The  feries  of  the  number  of  flars  contained  in  the  fe- 
veral  fe£lions  will  be  1.7.  19.  37. 61.  91.  &c.  which 
continued  to  n  terms,  the  fum  of  it,  by  the  differential  method, 

will  ht  na-\-n  ,  "——  d'  •\-n  .  ^—  •  ——   d'\  &c.  :   where  a  is 

2*23 

the  firft  term  d\  d'\  d"\  &c.  the  ift,  2d,  and  3d  differences. 
Then,  fince  tf=i,  ^'rz6,  d''-6,  d'" —  o,  the  fum  of  the 
feries  will  be  «\  Let  S  be  the  given  number  of  ftars;  i,  the 
diameter  of  the  bafe  of  the  field  of  view ;  and  B,  the 
diameter  of  the  bafe   of  the  great  re(5l:angular  cone ;    and,  by 

trigonometry,  we   (hall  have  Brn^^^^  1  field'     -^^^j  fince  the 
Vol.  LXXV.  I  i  '  field 


242  ■^'■^^''  Herschel  o?2  the 

field  of  view  of  a  telefcope  is  a  cone,  we  fliall  have  its  So- 
lidity to  that  of  the  great  cone  of  ftars,  formed  by  the  above 
conftrudion  as  the  fquare  of  the  diameter  of  the  bafc  of  the 
field  of  view,  to  the  fquare  of  the  diameter  of  the  bafe  of  the- 
great  cone,  the  height  of  both  being  the  fame  ;  and  the  ftars  in 
each  cone  being  in  the  ratio  of  the  lolidlty,  as  being  equally  fcat- 

tered  (/^),  we  have«=  a^B^S.  And  the  length  of  the  viiual 
ray  =  «  -  i,  which  was  to  be  determined. 


(I)  We  ought  to  remark,  that  the  periphery  ?5nd  bafe  of  the  cone  of  the  field 
of  view,  in  g.^ging,  would  in  all  probability  feldom  fall  exactly  on  fuch  ftars  as 
would  produce  a  perfed  equality  of  fituation  between  the  liars  contained  in  the 
fmalJ  and  the  great  cone;  and  that,  confequently,  the  folution  of  this  problem, 
where  we  fuppoie  the  ftars  of  one  cone  to  be  to  thofe  of  the  other  in  the  ratio 
of  the  folidity  on  account  of  their  being  equally  fcattered,  wili  not  be  ilricdy 
true.  But  it  fliould  be  remembered,  that  in  fmall  numbers,  where  the  different 
terminations  of  the  fields  would  moft  affeft  this  folution,  the  ftars  in  view  have 
always  been  afcertained  from  gages  that  were  often  repeated,  and  each  of  which 
confiftcd  of  no  lefs  than  tc-n  fields  fiiccellively  taken,  [o  that  the  different  deviations 
at  the  periphery  and  bafe  of  the  cone  vv^ould  certainly  compenfate  each  other 
fufficiently  for  the  purpofe  of  this  calculation.  And  that,  on  the  other  hand,  in 
higli  g^iges,  which  could  not  have  the  advantage  of  being  fo  often  repeated,  thefe 
deviations  would  bear  a  much  fmaller  proportion  to  the  great  number  of  ftars  in 
a  field  of  view  j  and  therefore,  on  this  account,  fuch  gages  may  very  juftly  be 
admitted  in  a  folution  where  pradical  truth  rather  than  mathematical  precifion 
is  the  end  we  have  in  view.  It  is  moreover  not  to  be  fuppofed  that  we  imagine 
the  ftars  to  be  aftually  arranged  in  this  regular  manner,  and,  returning  therefore 
to  our  general  hypothefis  of  their  being  equally  fcattered,  any  one  field  of  view 
promifcuoufly  taken  may,  in  this  general  fenfe,  be  fuppofed  to  contain  a  due 
proportion  of  them;  fo  that  the  principle  on  which  this  folution  is  founded  may 
therefore  be  faid  to  be  even  more  rigoroufiy  true  than  we  have  occafion  to  infill 
iipon  in  an  argument  of  this  kind. 


n^ 


ConJlru^iUn  of  the  liecivem,     '  243 


T^he  fame  other wfe. 

If  a  different  arrangement  of  the  flars  flioulc!  be  felc'6tecL 
fuch  as  that  in  fig.  2.  where  one  ftar  is  at  the  vertex  of  a  cone^; 
three  in  the  cuxu inference  of  the  fuft  feclion,  at  an  equal  dif- 
tance  from  the  vertex  and  from  each  other  •,  lix  in  the  circum- 
ference of  the  next  fe£llon,  with  one  in  the  axis  or  center; 
and  fo  on,  always  placing  three  ftars  in  a  lower  iecllon  in  fuch  a 
manner  as  to  form  an  equilateral  pyramid  with  one  above  them: 
then  we  fhall  have  every  ftar,  which  is  fufRciently  within 
the  cone,  furrounded  by  twelve  others  at  an  equal  dlflance  from 
the  central  ftar  and  from  each  other.  And  by  the  ditFerentlal 
method,  the  fum  of  the  two  feries  equally  continued,  into 
which  this  cone  may  be  refolved,  will  be  2/2^+ 1  i  «^  +  |«; 
where  n  flands  for  the  number  of  terms  in  each  feries.  To 
find  the  angle  which  a  line  vx^  paffing  from  the  vertex  v  over 
the  flars  t;,  n^  b^  /,  &c,  to  x,  at  the  outhde  of  the  cone,  makes 
with  the  axis ;  we  have,  by  conftrudion,  v  i  in  fig.  j. 
reprefenting  the  planes  of  the  firft  and  fecond  fedlions  = 
2  X  cof.30°  =  (p,  to  the  radius  p  j,  of  the  firfl  fe£lion  =;  i .   Hence 

it  will  be  ^^'  —  1  =vf  =  ivm  ;  or  vm=  2  n/(P^  -  i  :  and,  by 
trigonometry,   — ^rr=L=:T.     Where  T  is  the  tangent   of  the 

required  angle  to  the  radius  R  (c)  ;  and  putting  /  =:  tangent  of 

(c)  In  finding  this  angle  we  have  fuppofed  the  cone  to  be  generated  by  a 
revolving  reftangvilar  triangle  of  which  the  line  vx^  fig.  2.  is  the  hypotenufe ; 
but  the  ftars  in  the  fecond  feries  will  occafion  the  cone  to  be  contained  under  a 
waving  furface,  wherefore  the  above  fuppofition  of  the  generation  of  the  cone  is 
not  ftricftly  true ;  but  then  thefe  waves  are  fo  inconfiderable,  that,  for  the  pre- 
fent  piirpofe,  they  may  fafely  be  neglefted  in  this  calculation. 

I  i  2  half 


24^  Mr,  Herschel  ou  the 

T 
half  the  given  field  of  view,  it  will  be  —=:  B,  the  bafe  of  the 


\/~i 

cone.     And  — —^—d,  will  bean  expreflion  for  vp,  in  terms 

of  «yj-,    which  is  the  mutual  diftance  of  the  fcattered  flars. 

Then  having  —  —  n^  j^  I  n^  ■\- 1  ;?,    we  may    find    n  ;    whence 

idn  -  ^,  the  vifual  ray,  will  be  obtained. 

The  refult  of  this  arrangement  gives  a  fhorter  ray  than  that 
of  the  former ;  but  fince  the  difference  is  not  {o  confiderable  as 
very  materially  to  affe^Sl  the  conclufions,  I  (hall,  on  account  of 
the  greater  convenience,  make  ufe  of  the  firft. 


We  inhabit  the  -planet  of  a  Jlar  belonging  to  a  Compound  'Nebula 

of  the  third  for  tn, 

I  fhall  now  proceed  to  fliew  that  the  flupendous  fidereal  lyiLem 
we  inhabit,  this  extenlive  ftratum  and  its  fecondary  branch, 
confifthig  of  many  millions  of  ftars,  is,  in  all  probability,  a 
detached  Nebula.  In  order  to  go  upon  grounds  that  feem  to  me 
to  be  capable  of  great  certainty,  they  being  no  lefs  than  an 
ii£lual  furvey  of  the  boundaries  of  our  iidereal  fyflem,  which 
I  have  plainly  perceived,  as  far  as  I  have  yet  gone  round  it, 
every  where  terminated,  and  in  mofl  places  very  narrowly  too, 
it  will  be  proper  to  fhew  the  length  of  my  founding  line,  if  I 
may  fo  call  it,  that  it  may  appear  whether  it  was  fufticiently 
long  for  the  purpofe. 

In  the  moft  crowded  part  of  the  milky  way  I  have  had  fields 
of  view  that  contained  no  lefs  than  588  ftars  (^),  and  thefe  were 
continued  for  many  minutes,  fo  that  in  one  quarter  of  an  hour's 
time  there  pafled  no  lefs  than  1 16000  ftars  thiough  the  field  of 

(-V)   See  the  table  of  Gages,  p.  235. 

view 


ConJlni5lion  of  the  Heavens.  24^ 

view  of  my  telefcope  (t').  Now,  if  we  compute  the  length  of 
the  vKlial  ray  by  putting  S^jSS,  and  the  dlnmtter  of  the 

field  of  view  fifteen  minutes,  we  fhall  find  ?i  —  s/B'S  =  498  ;  fo 
that  it  appears  the  length  of  what  I  have  called  my  IbundingHne, 
or  ;/-  I,  was  probably  not  lefs  than  49^  times  the  diftance  of 
Sirius  from  the  fun.     The  lame  gage  calculated  by  the  fecond 

arrangement    of    ftars    gives  %/(??'— i  =  i. 41 421  ; 


Var  — 


tangent  of  31°  28'  SS" yll ''^  "^  =B=  280,69;   ~\-^  ^  d  - 

,81649;  —  r=23i63409,7=i/2'4- I  «'+ ?  «  ;  where   «  =  284,8 

nearly;  and  zdn-  1  —464,  the  vifual  ray. 

It  may  feem  inaccurate  that  we  fhould  found  an  argum.enton 
the  ftars  being  equally  fcattered,  when  in  all  probability  there 
mav  not  be  two  of  them  In  the  heavens,  whole  mutual  didance 
fhall  be  equal  to  that  of  any  other  two  given  ftars ;  but  it  fhould 
be  confidered,  that  when  we  take  all  the  flars  colledlively  there 
will  be  a  mean  diftance  which  may  be  afl'umed  as  the  general 
one;  and  an  argument  founded  on  fuch  a  fuppofition  will  have 
in  its  favour  the  greateft  probability  of  not  being  far  fliort  of 
truth.  What  will  render  the  fuppofition  of  an  equal  diftribu- 
tion  of  the  flars,  with  regard  to  the  gages,  ftill  lefs  expofed  to 
objedions  is,  that  whenever  the  flars  happened  either  to  be 
uncommonly  crowded  or  deficient  in  number,  fo  as  very  fud- 

{e)  The   breadth  of  my  fweep  was  2°  26',  to  which  muil  be  adtkd  15'  for  tvvo 

femi-diameters   of  the   field.      Then,  putting    161  r:^,    the    number  of  fields   in 

I  5  minutes  of  time  ;   ,7854  =  ^,   the  proportion  of  a  circle  to  i,   its  ciicumfcribed 

fquare;  (frrfine  of  74""  22',  the  polar  diftance  of  the  middle  of  the  fweep  reduced 

to  the  prefent  time  ;  and  588  =:S,  the  number  of  ftars  in  a  field  of  view,,  v/ehave 

«(pS  ,      .  . 

- — z:  110076  ftars, 
b 


^^4-6  ^^^'  Herschel  on  the 

denly  to  pafs  over  from  one  extreme  to  the  other,  the  gages 
were  redoced  to  other  forms,  fuch  as  tiie  border  gage,  the 
diftaiice-gage,  &c.  which  terms,  and  the  ule  of  fuch  gages, 
I  (hall  hereafter  find  an  opportunity  of  explaining.  And  none 
of  thoie  kinds  of  gages  have  been  admitted  in  this  table,  which 
contifts  only  of  fuch  as  have  been  taken  in  places  v/here  the 
liars  a|)parently  leemed  to  be,  in  general,  pretty  evenly  fcat- 
tercd  ;  and  to  increafe  and  decreafe  in  number  by  a  certain  gra- 
dual piogreffion.  Nor  has  any  part  of  the  heavens  containing 
a  clufter  of  ftars  been  put  in  the  gages  ;  and  here  I  mufi:  ob- 
lerve,  that  the  difference  between  a  crowded  place  and  a  clufter 
may  eaiily  be  perceived  by  the  arrangement  as  well  as  the  fize 
and  mutual  diilance  of  the  fears  ;  for  in  a  clufter  they  are 
generally  not  only  refembling  each  other  pretty  nearly  in  fize, 
but  a  certain  uniformity  of  diilance  alfo  takes  place  ;  they  are 
more  and  more  accumulated  towards  the  center,  and  put  on  all 
the  appearances  which  we  fhould  naturally  expevfl  from  a  num- 
ber of  them  colle6led  into  a  group  at  a  certain  diiliance  from 
VIS.  On  the  other  hand,  the  rich  parts  of  the  milky  way,  as 
well  as  thofe  in  the  diftant  broad  part  of  the  ftratum,  confifh 
of  a  mixture  of  ffars  of  all  poifible  fizes,  that  are  feemingly 
placed  without  any  particular  apparent  order.  Perhaps  we  might 
recolle6l,  that  a  greater  condenfation  towards  the  center  of  our 
fyftem  than  towards  the  borders  of  it  fhould  be  taken  into  con- 
fideration;  but,  with  a  nebula  of  the  third  form,  containing 
fuch  various  and  extenfive  combinations,  as  I  have  found  to 
take  place  in  ours,  this  circumftance,  which  in  one  of  the  firfl: 
form  would  be  of  coniiderable  moment,  may,  I  think,  be 
fafely  negledted.  However,  I  would  not  be  underftood  to  lay 
a  greater  ftrefs  on  thcfe  and  the  following  calculations  than  the 
principles  on  which  they  are  founded  wdll  permit ;  and  if  here- 
after 


Conjiruclion  cf  the  Heavens^  i\  j 

after  we  fliall  find  rcafoii,  from  experience  and  obfervation,  to 
believe  that  there  are  parts  of  our  {y{k&m:  where  the  ftars  are 
not  fcattered  in  the  manner  here  fuppofed,  we  ought  then  to 
make  proper  exceptions. 

But  to  return  :  if  Ibme  other  high  gage  be  fele6led  from  the 
table,  inch  as  472  or  34^,  the  length  of  the  vifual  ray  will  be 
found  461  and  415.  And  although,  in  confequence  of  what 
has  been  faid,  a  certain  degree  of  doubt  may  be  left  about  the 
arrangement  and  fcattering  of  the  flats,  yet  when  I  recolle£l, 
that  in  thofe  parts  of  the  milky  way  where  thefe  high  gages 
were  taken,  the  flars  were  neither  fo  fmall,  nor  fo  crowded, 
as  they  mufl:  have  been  on  a  fuppolirion  of  a  much  far- 
ther continuance  of  them,  wdien  certainly  a  milky  or  ne- 
bulous appearance  muft  have  come  on,  1  need  not  fear  to  have 
over-rated  the  extent  of  my  vifual  ray.  And  indeed  every 
thins:  that  can  be  faid  to  fliorten  it  will  onlv  contnicl  the  limits 
of  our  nebula,  as  it  has  in  moft  places  been  of  fufficieut  length 
to  go  far  beyond  the  bounds  of  it.  Thus,  in  the  fides  of  the 
ftratum  oppofite  to  our  fituatlon  in  it,  where  the  gages  often 
run  below  5,  our  nebula  cannot  extend  to  100  times  the  dif- 
tance  cf  Sirius ;  and  the  fame  telefcopc,  which  could  fhew  588 
ftars  in  a  field  of  view  of  15  minutes,  muft  certainly  have  pre- 
fented  me  alfo  with  the  flars  in  thefe  fituations  as  well  as  the 
former,  had  the}^  been  there.  If  we  fhould  anfwer  this  by  ob- 
ferving  that  they  might  be  at  too  great  a  diftance  to  be  per- 
ceived, it  will  be  allowing  that  there  mufl  at  leafl  be  a  vacancy 
amounting  to  the  length  of  a  vifual  ray  not  fhort  of  400  tlmiCS 
the  dlflance  of  Sirius  ;  and  this  is  amply  fuflicient  to  make  our 
nebula  a  detached  one.  It  is  true,  that  it  would  not  be  con- 
fiftent  confidently  to  affirm  that  we  were  on  an  iOand  unlefs 
we  had  adually  found  ourfelves  every  where  bounded  by  the 

ocean. 


248  Mr,  Herschel  on  the 

ocean,  and  therefore  I  fhall  go  no  farther  than  the  gages  will 
authorlfe ;  but  confideruig  the  little  depth  of  the  ftratum  in 
all  thofe  places  which  have  been  aftually  gaged,  to  which  muft 
be  added  all  the  intermediate  parts  that  have  been  viewed  and 
tonud  to  be  much  like  the  reft,  there  is  but  little  room  toexpedt 
a  connection  between  our  nebula  and  any  of  the  neighbouring 
ones.  I  ouglit  alio  to  add,  that  a  telefcope  with  a  much  larger 
aperture  than  my  preient  one,  grafping  together  a  greater  quan- 
tity of  light,  and  thereby  enabling  us  to  fee  farther  into  fpace, 
will  be  the  lureft  means  of  compleating  and  eftablifliing  the 
arguments  that  have  been  ufcd  :  for  if  our  nebula  is  not  abfo- 
lutely  a  detached  one,  I  am  firmly  periuaded,  that  an  inftru- 
rnent  may  be  made  large  enough  to  difcover  the  places  where 
the  ftars  continue  onwards.  A  \txy  bright  milky  nebulofity 
niufl  there  undoubtedly  come  on,  fuice  the  ftars  in  a  field  of  view 
will  increafe  in  the  ratio  of  n\  greater  than  that  of  the  cube 
of  the  vifual  ray.  Thus,  if  588  frars  in  a  given  field  of  viev/ 
are  to  be  Icen  by  a  ray  of  497  times  the  diftance  of  Sirius  ; 
when  this  is  lengthened  to  1000,  which  is  but  little  more 
than  double  the  former,  the  number  of  flars  in  the  fame  field 
of  view  will  be  no  iels  than  4774  :  for  when  the  vifual  ray  r 

is  given,   the  number  S  of  flars  will  be::=^;  where  72  — r+  i ; 

and  a  telefcope  with  a  three-fold  power  of  extending  into  fpace, 
or  with  a  ray  of,  1500,  which,  I  think,  may  eafily  be  con- 
flrufted,  will  give  us  16096  ftars.  Now,  thefe  would  not  be 
fo  clofe  but  that  a  good  power  applied  to  fuch  an  inftrument 
might  eafily  dlftinguifh  them  ;  for  they  need  not,  if  arranged 
in  regular  Spares,  approach  nearer  to  each  other  than  6^^,27; 
but  what  would  produce  the  milky  nebulofity  which  I  have 
■mentioned  is  the  numberlefs  flars  beyond  them,  which  in  one 

refpedl 


Confirudtlon  of  the  Heavens*  249 

refpe£t  the  vifual  ray  might  alfo  be  faid  to  reach.  To  make 
this  appear  we  muft  return  to  the  naked  eye,  which,  as  wc 
have  before  eftimated,  can  only  fee  the  flars  of  the  feventh 
magnitude  fo  as  to  diftlnguifh  them  ;  but  It  is  neverthelels  very 
evident  that  the  united  luftre  of  millions  of  flars,  iuch  as  [ 
fuppofe  the  nebula  in  Aiidromedato  be,  will  reach  our  fight  in 
the  fhape  of  a  very  fmall,  faint  nebuloiity  ;  fmce  the  nebula  of 
which  I  fpeak  may  eafiiy  be  ittw  in  a  line  evening.  In  the 
■fame  manner  my  prefent  telefcope,  as  I  have  argued,  has  not 
only  a  vifual  ray  that  will  reach  the  flars  at  497  times  the  dif- 
tance  of  Sirius  fo  as  to  diftinguifh  them  (and  probably  much 
farther),  but  alfo  a  power  of  iliewing  the  united  luilre  of  the 
accumulated  flars  that  compofe  a  milky  nebulofity,  at  a  diilance 
far  exceeding  the  former  limits ;  fo  that  from  thelc  conildera- 
tions  it  appears  again  highly  probable,  that  my  prefent  telefcope, 
not  fhewing  fuch  a  nebulofity  in  the  milky  way,  goes  already  far 
beyond  its  extent :  and  conlequently,  much  more  would  an 
inftrument,  fuch  as  I  have  mentioned,  remove  all  doubt  on 
the  fubje£t,  both  by  fhewing  the  flars  in  the  continuation  of 
the  flratum,  and  by  expofing  a  very  flrong  milky  nebuMty 
beyond  them,  that  could  no  longer  be  miflaken  for  the  dark 
ground  of  the  heavens. 

To  thefe  arguments,  which  refl  on  tlie  firm  bafis  of  a  feries 
of  obfervation,  we  may  add  the  following  confiderations  drawn 
from  analogy.  Among  the  great  number  of  nebuliE  which  I 
have  now  already  feen,  amounting  to  more  than  900,  there 
are  many  which  in  all  probability  are  equally  extenfive  with 
that  which  we  inhabit ;  and  yet  they  are  all  feparated  from  each 
ether  by  very  confiderable  intervals.  Some  indeed  there  are 
that  feem  to  be  double  and  treble.;  and  though  with  moll  of 
thefe  it  may  be,  that  they  are  at  a  very  great  diilance  from  each 

Vol.  LXXV.  K  k   '  other. 


2^o  Mr.  Herschel  on  the 

other,  yet  we  allow  that  fome  fuch  conjun<£lions  really  arc  to 
bs  found ;  nor  is  this  what  we  mean  to  exclude.  But  then 
thefe  .compound  or  double  nebulae,  which  are  thofe  of  the  third 
and  fourth  forms,  flill  make  a  detached  link  in  the  great  chain. 
It  is  alfo  to  he  fuppofed,  that  there  may  fti!l  be  fome  thinly 
fcattered  folitarv  flars  between  the  lar^e  interftlces  of  nebulse, 
which,  beuig  fituated  fo  as  to  be  nearly  equally  2ttYd.0:ed.  by  the 
feverai  clufters  when  they  were  forming,  remain  unaffociated. 
And  though  we  cannot  expect-  to  fee  thele  ftars,  on  account  of 
their  vaft  diftance,  yet  we  may  well  prefum.e,  that  their  num- 
ber cannot  be  very  contiderable  in  com-parifon  to  thofe  that  are 
already  drawn  into  fyflems ;  which  conjetlure  is  alfo  abun- 
dantly confirmed  in  fituatlons  where  the  nebulas  are  near  enough 
to  have  their  flars  vifible  ;  for  they  are  all  infulated,  and  gene- 
rally to  be  i'een  upon  a  very  clear  and  pure  ground,  without 
any  ftar  near  them  that  might  be  fuppofed  to  belong  to  them. 
And  though  I  have  often  feen  them  in  beds  of  flars,  yet  from 
the  fize  of  thefe  latter  we  may  be  certain,  that  they  were 
much  nearer  to  us  than  thofe  nebulae,  and  belonged  undoubtedly 
to  our  own  fyftem. 


A  delineation  of  our  nebula,  by  an  application  of  the  gages 
in  the  manner  which  has  been  propofed  to  be  done  In  my  for- 
mer paper,  may  now  be  attempted,  and  the  following  table  is 
calculated  for  this  purpofe.  It  gives  us  the  length  of  the  vifual 
ray  for  any  number  of  ftars  in  the  field  of  view  contained  in 
the  third  column  of  the  foregoing  table  of  gages  from  _V  to 
100000.  If  tlie  number  required  is  not  to  be  found  in  the  iirft 
4  column 


ConJlru6lion  of  the  Heavens,  251 

column  of  this  table,  a  proportional  mean  may  be  taken  be- 
tween the  two  neareft  rays  in  the  fecond  column,  without  any 
material  error,  except  in  the  few  laft  numbers.  The  calcula- 
tions of  refolvable  and  milky  nebulofity,  at  the  end  of  the 
table,  are  founded,  the  firft,  on  a  fuppofition  of  the  ftars 
being  fo  crowded  as  to  have  only  a  fquare  fecond  of  fpace 
allowed  them;  the  next  afligning  them  only  half  a  fecond 
fquare.  However,  we  (hould  confider  that  in  all  probability  a 
very  different  accumulation  of  flars  may  take  place  in  different 
nebulae  ;  by  which  means  fome  of  them  may  aflume  the  milky 
appearance,  though  not  near  fo  far  removed  from  us ;  while 
clufters  of  ffars  alfo  may  become  refolvable  nebulas  from  the 
fame  caufe.  The  diflindnefs  of  the  inflrument  is  here  alfo 
concerned  ;  and  as  telefcopes  with  large  apertures  are  not  eafily 
brought  to  a  good  figure,  nebulous  appearances  of  both  forts 
may  probably  come  on  much  before  the  diflance  annexed  to 
them  in  the  table. 


K  k    2  TABLE 


252 


Mr,  Herschel  on  the 


TABLE       11. 


Stars  in 

Vifu;il 

Stars 

Rav. 

Stars. 

Rav. 

Stars. 

Ray. 

Stars. 

Ray.  • 

the  field 

T-'l  «' 

VAj. 

''  T 

t86 

71 
72 

245 
246 

210 

3S^ 
358 

700 

551  . 

o,i 

27 

0^ 

32 

188 

220 

800 

1   o,2 

34 

33 

190 

73 

247 

230 

363 

coo 

57  3  i 

0.3 

39 

34 

192 

74 

249 

240 

363 

1000 

593 

•  o,4 

43 

35 

193 

75 

250 

2.50 

374 

1 0000 

1280 

0.5 

4^ 

3'^ 

195 

76 

251 

260 

378 

I 00000 

2758 

o,6 

49 

37 

197 

77 

252 

270 

3'^?> 

o,7 

52 

38 

199 

78 

253 

280 

388 

o,8 

54 

39 

201 

79 

254 

290 

393 

0,9 

5^ 

40 

202 

80 

255 

300 

397 

1 

I 

S8 

41 

204 

81 

256 

310 

401 

2 

74 

42 

206 

82 

257 

320 

406 

636175 

[5112 

3 

8,S 

43 

207 

83 

258 

330 

410 

or 

4 

93 

44 

209 

84 

259 

340 

414 

refolvable 

5 

lOI 

4^; 

280 

85 

260 

350 

418 

nebulofity 

6 

107 

46 

212 

86 

261 

360 

422 

7 

113 

47 

214 

■87 

262 

370 

426 

8 

118 

48 

215 

88 

263 

380 

430 

9 

123 

49 

217 

89 

264 

390 

433 

10 

127 

50 
51 

218 

90 

265 

400 

437 

II 

131 

219 

91 

266 

410 

441 

12 

135 

52 

221 

92 

267 

420 

444 

2544700 

•\ 

13 

14 

139 

142 

53 

54 

222 
224 

93^ 

94 

268 
269 

430 
440 

448 

451 

or 

milky 

[siis 

IS 

ia6 

55 

225 

95 

270 

450 

455 

nebulofity 

J 

16 

149 

56 

226 

96 

271 

460 

458 

17 

152 

S7 

228 

97 

272 

470 

461 

18 

15s 

58 

229 

98 

273 

480 

464 

19 

158 

59 

230 

99 

274 

490 

468 

20 

160 

60 

232 

100 

275 

500 

471 

21 

163 

61 

233 

110 

284 

510 

474 

22 

166 

62 

234 

120 

291 

520 

477 

j   03 

168 

63 

236 

130 

300 

530 

480 

24 

170 

64 

237 

140 

308 

540 

483 

♦   25 

173 

65 

238 

150 

315 

550 

486 

26 

175 

66 

239 

160 

322 

560 

489 

27 

177 

67 

240 

170 

328 

570 

492 

28 

180 

68 

242 

180 

335 

580 

495 

29 

182 

69 

243 

190 

3+1 

590 

498 

30 

184 

70 

244 

200 

347 

600 

500 

Scdiion 


ConftniLt'iGn  of  the  Heavens.  253 

SeSlJon  of  our  fidereal  fyjienu 

By  taking  out  of  this  table  the  vlfnal  rays  which  anfwcr  to 
the  gages,  and  applying  lines  proportional   to  them  around  a 
point,  according   to  their  refpeclive  right  afcenfions  and  north 
polar  diftances,  we  may  delineate  a  folid  by  means  of  the  ends 
of  thefe  lines,  which   will  give  us   fo  many  points  in  its  fur- 
face ;  1  Ihall,  however,  content  myfelf  at  prefent  with  a  fec- 
tion  only.     I  have  taken  one  which  paflcs  through  the  poles  of 
our  fyftem,  and  is   at   re6tangles   to   the   conjunction    of   the 
branches  which  I  have  called  its  length.     The  name  of  poles 
feemed  to  me  not  improperly  applied  to  thofe  points  which  are 
90  degrees  diftant  from  a  circle  pafling  along  the  rnilky  way, 
and  the  north  pole  is  here  affumed  to  be  lituated  in  R,A.  186^ 
and  P.D.  58°.     The  fe6tion  reprefented   in  fig.  4.  is  one  which 
makes  an  angle  of  ^^S  degrees  with  our  equator,   c roiling  it  in 
124I  and  3041  degrees.     A  celeftial  globe, .  adj ufted  to  the  lati- 
tude of  55°   north,  and  having  a-  Ceti  near  the  meridian,  will 
have  the  plane  of  this  fedlion  pointed  out  by  the  horizon,  and 
the  gages  which  have  been   ufed   in  this  delineation  are   thofe 
which  in  table  I.,  are  marked   by.  afleriiks.     When  the  vifual 
rays  anfwering  to  them  are  taken  out  of  the  fecond  table,  they 
mufl:'  be  proje6led  on  the   plane  of  the  horizon  of  the  latitude 
which   has  been  pointed  out ;  and  this  may  be  done  accurately 
enough  for  the  prefent  purpofe  by  a  globe  adjufted  as  above  di^ 
reeled;  for  as  gages,  exadlly  in  the  plane  of  the  feclion,  were 
often  wanting,  1  have  ufed  many  at  lome  fmall  dllfance  above 
and  below  the  fame,  for  the  fake  of  obtalninf7  more  delineatino; 
points ;  and  in   the  figure  the  flars  at   the  borders  which  are 
larger  than  the  reft  are  thofe  pointed- out  by  the  gages.     1  hi 
2  ,  inter- 


2  cd  Mr.  Herschel  on  the 

intermediate  parts  are  filled  up  by  fmaller  fiars  arranged  in 
iT:raiglit  lines  between  the  gaged  ones.  The  delineating  points, 
though  pretty  nuinerous,  are  not  fo  clofe  as  wc  might  wifh ; 
it  is  however  to  be  hoped  that  in  fome  future  time  this 
branch  of  aftronomy  will  become  more  cultivated,  fo  that  we 
may  have  gages  for  every  quarter  of  a  degree  of  the  heavens  at 
lead,  and  thefe  often  repeated  in  the  moft  favourable  circum- 
ftances.  And  whenever  that  fhall  be  the  cafe,  the  delineations 
may  then  be  repeated  with  all  the  accuracy  that  long  experience 
may  enable  us  to  Introduce ;  for,  this  fubjed  being  fo  new,  I 
look  upon  what  is  here  given  partly  as  only  an  example  to 
illuftrate  the  fpirit  of  the  method.  From  this  figure  how- 
ever, which  I  hope  is  not  a  very  inaccurate  one,  we  may  fee 
that  our  nebula,  as  we  obferved  before,  is  of  the  third  form  ; 
that  is :  A  very  extenjive,  branchings  compound  Congenes  of 
many  millions  of  Jiars  \  which  moft  probably  owes  its  origin  to 
many  remarkably  large  as  well  as  pretty  ciofely  fcattered  fmali 
liars,  that  may  have  drawn  together  the  reft.  Now,  to  have 
fome  idea  of  the  wonderful  extent  of  this  fyftem,  I  mufl  ob- 
ferve  that  this  fe£Hon  of  it  is  drawn  upon  a  fcale  where  the 
diflance  of  Sirius  is  no  more  than  the  8oth  part  of  an  inch  ;  fo 
that  probably  all  the  ftars,  which  in  the  fineft  nights  we  are 
able  to  diftinguifh  with  the  naked  eye,  may  be  comprehended 
within  a  fphere,  drawn  round  the  large  ftar  near  the  middle, 
reprefenting  our  fituation  in  the  nebula,  of  lefs  than  half  a 
quarter  of  an  inch  radius. 

The  Origin  of  nebulous  Strata. 

If  it   wete  poflible  to  diftingulfh  between  the  parts   of  an 
indefinitely  extended  whole,  the  nebula  we  inhabit  might  be 

faid 


ConJlruSlion  of  the  Heavens.  .  255 

faid  to  be  one  that  has  fewer  marks  of  profound  antiquity  upon 
it  than  the  reft.  To  explain  this  idea  perhaps  more  clearly,  we 
fhould  recoiled  that  the  condenlation  of  clufters  of  ftars  has 
been  afcribed  to  a  gradual  approach  ;  and  whoever  refle6ls  on 
the  numbers  of  nges  that  muft  have  paft  before  fome  of  the 
clufters,  that  will  be  found  in  my  intended  catalogue  of  them, 
could  be  fo  far  condenfed  as  we  find  them  at  prcfent,  will  not 
wonder  if  I  afcribe  a  certain  air  of  youth  and  vigour  to  many 
very  regularly  fcattered  regions  of  our  fidereal  ftratum.  There 
are  moreover  many  places  in  it  where  there  is  the  greateft 
reafon  to  believe  that  the  ftars,  if  we  may  judge  from  ap- 
pearances, are  now  drawing  towards  various  fecondary  centers, 
and  will  in  time  feparate  into  different  clufters,  fo  as  to  occa- 
fion  many  fub-divifions.  Hence  we  may  furmife  that  when  a 
nebulous  ftratum  confifts  chiefly  of  nebuliE  of  the  firft  and  fe* 
cond  form,  it  probably  owes  its  origin  to  what  may  be  called 
the  decay  of  a  great  compound  nebula  of  the  third  form  ;  and 
that  the  fub-divifions,  which  happened  to  It  in  length  of  time, 
cccafioned  all  the  fmall  nebulae  which  Iprung  from  it  to  lie  in  a 
certain  range,  according  as  they  were  detached  from  the  pri- 
mary one.  In  like  manner  our  fyftem,  after  numbers  of  ages, 
may  very  poflibly  become  divided  fo  as  to  give  rife  to  a  ftratum 
of  two  or  three  hundred  nebula ;  for  it  would  not  be  difficult 
to  point  out  fo  many  beginning  or  gathering  clufters  in  It  (/). 
This  view  of  the  prefent  fubje^l  throws  a  confiderable  light 
upon   the  appearance  of  that   remarkable  coUedlion  of  many 

(y)  Mr.  MicHELL  has  alfo  confidered  the  ftars  as  gathered  together  info 
groups  (Phil.  Tranf.  voU  LVII.  p.  249.)  j  which  idea  agrees  with  the  fub-diviCcn 
of  our  great  fyftem  here  pointed  out.  He  founds  an  elegant  proof  of  this  on 
the  computation  of  probabilities,  and  mentions  the  Pleiades,  the  Pra*fepc  Cancri, 
and  the  nebula  (or  chifter  of  ftars)  in  the  hilt  of  Perfeus's  fuord,  as  inftanccr. 

hundreds 


256  Mr,  Herscviel  on  the 

hundreds  of  nebulae  which  are  to  be  feen  in  what  I  hn.ve  called 
:  the  nebulous  flratum  of  Coma  Berenices.     It  appears  from  the 
extended  and  branching  figure  of  our  nebula,  that  there  is  room 
for  the  decompofed  fmail  nebula  of  a  large,  reduced,  former 
great  one  to  approach  nearer  to  us  in  the  fides  than  in  other 
parts.     Nay,  pofiibly,  there   might  originally  be  another  very- 
large  joining  branch,  which  in  time  became  feparated  by  the 
condenfation  of  the  ftars ;  and  this  may  be  the  reafon  of  the 
! little  remaining  breadth  of  our  fyftem  in  that  very  place:  for 
.  the  nebulae  of  the  ftratum  of  the  Coma  are  brightcfh  and  mofi: 
crowded  juft  oppofite  our  fituation,  or  in  the  pole  of  our  fyflem. 
As  foon  as  this  idea  was  fuggefted,  I  tried  alfo  the  oppofite  pole, 
where  accordingly  I  have  met  with  a  great  number  of  nebula, 
1  though  under  a  much  more  fcattered  form. 

* 

jtin'Opening  in  the  heavens, 

^  Some,  parts  of  our  fyftem  indeed  feem  already  to  have  fuf- 

"tained  greater  ravages  of  time  than  others,  if  this  way  of  ex- 

prefling  myfelf  may  be  allowed  ;  for  inftance,  in  the  body  of 

the  Scorpion  is  an  opening,  or  hole,  which  is  probably  owing  to 

this  caufe.     1  found  it  while  I  was  gaging  in  the  parallel  from 

112  to  114  degrees  of  north  polar  diftance.     As  I  approached 

the  milky  way,  the  gages  had  been  gradually  running  up  from 

9,7  to  17,1  ;  when,  all  of  a  fudden,  they  fell  down  to  nothing, 

a  very  few  pretty  large  ftars  excepted,  which  made  them  Ihew 

0,5,  0,7,    1,1,   1,4,    1,8;  after   which   they  again  rofe  to  4,7, 

13,5,  20,3,  and  foon  after  to  41,'T.      This  opening  is  at  leaft 

4  degrees  broad,  but   its  height  I  have  not  yet  afcertained.     It 

.is  remarkable,  that   the   80  Nebuleufe  fans  eto'iks  of  the  Con^ 

mo'ijance  des  Tewps,  which  is  one  of  the  richeft  and  mofl  com- 

prefTed 


ConfiruSlwn  of  the  Heavens,  2^j 

prefled  cluHers  of  fmall  ftars  I  remember  to  have  feen,  is 
{ituated  juft  on  the  weftern  border  of  it,  and  would  ahnoft  au- 
thorife  a  fufpiclon  that  the  liars,  of  which  it  is  compofed,  were 
collected  from  that  place,  and  had  left  the  vacancy.  What  adds 
not  a  little  to  this  furmife  is,  that  the  fame  pha?nomcnon  is 
once  more  repeated  \vith  the  fourth  clufter  of  ftars  of  the 
Connoijfance  dcs  Temps ;  which  is  alfo  on  the  weftern  border  of 
another  vacancy,  and  has  moreover  a  fmall,  miniature  clufter, 
or  eafily  refolvable  nebula  of  about  2|  minutes  in  diameter, 
north  following  it,  at  no  very  great  diftance. 


Phenomena  at  the  Poles  of  our  Nebula, 

* 

I  ought  to  obferve,  that  there  is  a  remarkable  purity  or  clear- 
nefs  in  the  heavens  when  we  look  out  of  our  flratum  at  the 
fides;  that  is,  towards  Leo,  Virgo,  and  Coma  Berenices,  on  one 
hand,  and  towards  Cetus  on  the  other ;  whereas  the  ground 
of  the  heavens  becomes  troubled  as  we  approach  towards  the 
length  or  height  of  it.  It  was  a  good  while  before  I  could 
trace  the  caufe  of  thefe  ph^enomena ;  but  (ince  I  have  beeii 
acquainted  with  the  fhape  of  our  fyftem,  it  is  plain  that  thefe 
troubled  appearances,  when  vv^e  approach  to  the  fides,  are  eafily 
to  be  explained  by  afcribing  them  to  fome  of  the  diilant,  flrag- 
gling  ftars,  that  yield  hardly  light  enough  to  be  difl:inguiOied. 
And  1  have,  indeed,  often  experienced  this  to  be  a£lually  the 
caufe,  by  examining  thefe  troubled  fpots  for  a  long  w^iile  toge- 
ther, when,  at  laft,  I  generally  perceived  the  flars  which  occa- 
fioned  them.  But  when  we  look  towards  the  poles  of  our 
fyflem,  where  the  vifual  ray  does  not  graze  along  the  fide,  the 

Vol.  LXXV.  L  i  flragglin 


g 


2c^S  Mr.  Herschel  on  iht 

ftraggling  ftars  of  coiirfe  will  be  very  few  in  number ;  ancl^ 
therefore  the  giound  of  the  heavens  will  aflume  that  purity 
which  1  have  always  obferved  to  take  place  in  thofe  regions. 

Enumeration  of  very  compowid  Nebula  or  Milky^Ways, 

As  we  are  ufed  to  call  the  appearance  of  the  heavens,  whers- 
it  is  furrounded  Vv'ith  a  bright  zone,  the  Milky-V/ay,  it  may 
not  be  amifs  to  point  out  fome  other  very  remarkable  Nebulas- 
which  cannot  well  be  lefs,  but  are  probably  much  larger  thaiv 
our  own  fyftem  ;  and,  being  alfo  extended,  the  inhabitants  oF 
the  planets  tliat  attend  the  ftars  which  compofe  them  muft 
likewife  perceive  the  fame  phenomena.  For  which  reafon  they 
may  alfo  be  called  milky-ways  by  way  of  difiindlion. 

My  opinion  of  their  fize  is  grounded  on  the  following  ob- 
fervations.  There  are  many  round  nebulae,  of  the  firil:  form,. 
of  about  five  or  fix  minutes  in  diameter,  the  flars  of  which  I^ 
can  lee  very  diftindlly ;  and  on  comparing  them  with  the  vifual 
yay  calculated  from  fome  of  my  long  gages,  I  fuppofe,  by  the  ap- 
pearanceof  the  fmall  ftars  in  thofe  gages,  that  the  centers  of  thefe 
round  nebulae  may  be  600  times  the  diflance  of  Sirius  from  us. 

In  eftimatins;  the  diflance  of  luch  cluflers  I  confulted- 
rather  the  comparatively  apparent  fize  of  the  fl-ars  than 
their  mutual  diftance;  for  the  condenfation  in  thefe  cluifers- 
being  probably  much  greater  than  in  our  own  fyftem,  if  we 
"were  to  overlook  this  circumfi:auce  and  calculate  b}^  their  appa- 
rent compreffion,  where,  in  about  fix  minutes  diameter,  there 
are  perhaps  ten  or  more  ftars  in  the  line  of  meafures,  we  fhould 
find,  that  on  the  fuppofition  of  an  equal  fcattering  of  the  flars- 
throughout  all  nebulae,  the  diflance  of  the  center  of  fuch  a 
clufter  from  us  could  not  be  lefs  than  6000  times  the  diflance 

/ 


Conflrii^llon  of  the  Ihavehs,  i^p' 

of  Sirius.  And,  perhaps,  in  putting  it,  by  the  apparent  iize 
of  the  flars,  at  600  only,  I  may  have  conliderably  under-rated 
it ;  but  my  argument,  if  that  ihould  be  the  cafe,  will  be  fo 
much  the  ftronger.     Now  to  proceed, 

Some  of  thefe  round  nebulae  have  others  near  them,  perfeiflly 
fuiiilar  in  form,  colour,  and  the  diftribut'ioii  of  flars,  but  of  only 
half  the  diameter:  andthe  flars  in  them  fecm  to  be  doubly  crowded, 
and  only  at  about  half  the  diilance  from  each  other  :  they  arc 
indeed  lb  fmall  as  not  to  be  vifible  without  the  utmoft  attention, 
I  fuppofe  thefe  miniature  nebulae  to  be  at  double  the  diftance  of 
the  tirft.     An  inifance,  equally  remarkable   and  inflruclive,  is 
a  cafe  where,  in  the  neighbourhood  of  two  fuch  nebulas  as 
have  been  mentioned,  I  met  with  a  third,  fimllar,  refolvable, 
but  much  fmaller  and  feiinter  nebula.     The  flars  of  it  are  no 
longer  to  be  perceived  ;  but  a  refemblance  of  colour  with  the 
former  two,  and  its  diminished  fize  and  light,  may  well  per- 
mit us  to  place  it  at  full  twice  the  diiliance  of  the  fecond,  or 
about  four  or  five  times  that  of  the  lirfl:.     And  yet  the  nebil- 
lofity  is  not  of  the  milky  kind ;  nor  is  it  {o  much  as  difficultly 
refolvable,  or  colourlefs.     Now,  in  a  few  of  the  extended  ne- 
bulae, the  light  changes  gradually  fo  as  from  the  refolvable  to 
approach  to  the  milky   kind ;  which  appears   to  me  an  indica- 
tion that  the  milky  light  of  nebulae  is  owing  to  their  much 
greater  diflance.     A  nebula,  therefore,  whofe  light  Is  perfedlly 
milky,  cannot  well  be  fuppofed  to  be  at  lefs  than  fix  or  eight 
thoufand  times  the  diflanCe  of  Sirius ;  and  though  the  numbers 
here  afiumed  are  not  to  be  taken  otherwife  than  as  very  coarfe 
eftimates,  yet  an  extended  nebula,  which  in  an  oblique  fitua- 
tiofl,  where  it  is  poffibly  fore-fhortened  by  one-half,  two-thirds, 
or  Hiree- fourths  of  its  length,  fubtends  a  degree  or  more  in 
♦  L  1  i;  diameter, 


i6o  Mr.  Herschel  on  the 

diameter,  cannot  be  otherwife  than  of  a  wonderful  magnitude, 
and  may  well  outvie  our  milky-way  in  grandeur. 

The  firft  I  (hall  mention  is  a  milky  Ray  of  more  than  a  de- 
gree in  length.  It  takes  k  (Fl.  52.)  Cygni  into  its  extent,  to 
the  north  of  which  it  is  crookedly  bent  fo  as  to  be  convex 
towards  t'le  following  fide  ;  and  the  light  of  it  is  pretty  intenfe. 
To  the  fouth  of  k  it  is  more  diffufed,  lefs  bright,  and  lofes 
itfelf  with  iome  extenfion  in  two  branches,  I  believe ;  but  for 
want  of  light  I  could  not  determine  this  circumftance.  The 
northern  half  is  near  two  minutes  broad,  but  the  fouthern  is 
not  fufficiently  defined  to  afcertain  its  breadth. 

The  next  is  an  extremely  faint  milky  Ray,  above  |  degree 
long,  and  8  or  io^  broad;  extended  from  north  preceding  to 
fouth  following.  It  makes  an  angle  of  about  30  or  40  degrees 
with  the  meridian,  and  contains  three  or  four  places  that  are 
brighter  than  the  reft.  The  flars  of  the  Galaxy  are  fcattered 
over  it  in  the  fame  manner  as  over  the  reft  of  the  heavens.  It 
follows  £  Cygni  1 1,5  minutes  in  time,  and  is  2°  19^  more  fouth. 

The  third  is  a  branching  Nebulofity  of  about  a  degree  and  a 
half  in  right  afcenlion,  and  about  48^  extent  in  polar  diftance. 
The  following  part  of  it  is  divided  into  feveral  ftreams  and 
windings,  which,  after  feparating,  meet  each  other  again 
towards  the  fouth.  It  precedes  f  Cygni  i6'  in  time,  and  is 
1°  16^  more  north.  I  fuppofe  this  to  be  joined  to  the  preceding 
one ;  but  having  obferved  them  in  different  fweeps,  there  was 
no  opportunity  of  tracing  their  conne£llon. 

The  fourth  is  a  faint,  extended  milky  Ray  of  about  i^^'In 
length,  and  12'  in  breadth.  It  is  brighteft  and  broadeft  in  the 
middle,  and  the  ends  lofe  themfelves.  It  has  a  fmall,  round, 
very  faint  nebula juft  north  of  it;  and  alfo,  in  another  place, 
a  fpot,  brighter  than  the  reft,  almoft  detached  enough  to  form 

a  different 


Conjlruciton  of  the  Heavens,  261 

a  different  nebula,  but  probably  belonging  to  the  great  one. 
The  Ray  precedes  a  Trlanguli  18', 8   in  time,  and  is  55'  more 
north.     Another  obfervation  of  the  fame,  in  a  finer  evening, 
mentions  its  extending   much   farther  towards  the  fouth,  and' 
that  the  breadth  of  it  probably  is  not  lefs  than  half  a  degree  ; . 
but  being  (liaded  away  by  imperceptible  gradations,  it  is  ditii-- 
cult  exactly  to  affign  its  limits. 

The  fifth  is  a  Streak  of  light  about  27''  long,,  and  in  the 
brlghteft  part  3  or  4^  broad.  The  extent  is  nearly  in  the  meri- 
dian, or  a  little  from  fouth  preceding  to  north  following.  It 
follows  jS  Ceti  5^,9  in  time,  and  is  2°  43'' more  fouth.  The 
fituation  is  {q  low,  that  it  would  probably  appear  of  a  much 
greater  extent  in  a  higher  altitude. 

The  lixth  is  an  extenfive  milky  Nebulofity  divided  into  two 
parts;  the  moil  north  being  the  ftrongeft.  Its  extent  exceeds 
15';  the  fouthern  part  is  followed  by  a  parcel  of  ftars  which 
1  fuppofe  to  be  the  8th  of  the  Cunnoijfance  des  Temps,, 

The  feventh  is  a  wonderful,  extenlive  Nebulofity  of  the  milky 
kind.  There  are  feveral  ftars  vifible  in  it,  but  they  can  have 
no  connection  with  that  nebulofity,  and  are,  doubtlefs,  belong- 
ing to  our  own  fyflem  fcattered  before  it.  It  is  the  17th  of 
the  Connoijfance  des  Temps, 

In  the  lift  of  thefe  muft  alfo  be  reckoned  the  beautiful  Ne- 
bula of  Orion.  Its  extent  is  much  above  one  degree  ;  the 
eaftern  branch  paffes  between  two  very  fmall  ftars,  and  runs  on 
till  it  meets  a  very  bright  one.  Clofe  to  the  four  fmall  itars, 
which  can  have  no  connection  with  the  nebula,  is  a  total  black-  - 
nefs ;  and  within  the  open  part,  towards  the  north-eaftj  is  a 
diftind,  fmall,  faint  nebula,  of  an  extended  (hape,  at  a  diftance 
from  the  border  of  the  great  one,  to  which  it  runs  in  a.  parallel 
4  ^  direction,, 


'2%i  Mr.  Herschel  on  the 

direction,  refembling  the  (hoals  that  are  feen  near  the  coafts  of 

fome  iflands. 

The  nhith  is  that  hi  the  girdle  of  Andromeda,  which  is  un- 
doubtedly the  nearefl:  of  all  the  great  nebulse ;  its  extent  is 
above  a  degree  and  a  half  in  length,  and,  in  even  one  of  the 
narrowed  places,  not  lefs  than  i6^  in  breadth.  The  brighteft 
part  of  it  approaches  to  the  refolvable  nebuloiity,  and  beghis 
to  fliew  a  faint  red  colour  ;  which,  from  many  obfervations  on 
the  colour  and  magnitude  of  nebuliE,  J  believe  to  be  an  indica- 
tion that  its  diflance  in  this  Coloured  part  does  not  exceed  2000 
times  the  diflance  of  Sirius.  There  is  a  very  confiderable, 
broad,  pretty  faint,  fmali  nebula  near  it ;  my  Sifter  difcovered 
it  Augufl:  27,  178  ;,  with  a  Newtonian  2-feet  fweeper.  It  flicws 
the  fame  faint  colour  with  the  great  one,  and  is,  no  doubt,  in 
the  neighbourhood  of  it.  It  is  not  the  3 2d  of  the  Connoiffance' 
des  Temps  ;  which  is  a  pretty  large  round'  nebula,  much  con- 
denfed  in  the  middle,  and  fouth  following  the  great  one  ;  but 
this  is  about  two-thirds  of  a  degree  north  preceding  it,  in  a 
line  parallel  to  /3  and  v  Andromedie. 

To  thefe  may  be  added  the  nebula  in  Vulpecula :  for,  though 
its  appearance  is  not  large,  it  is  probably  a  double  flratum  of 
ftars  of  a  very  great  extent,  one  end  whereof  is  turned  towards 
us.  That  it  is  thus  fituated  may  be  furmifed  from  its  contain- 
ing, in  diiferent  parts,  nearly  all  the  three  nebulofities ;  viz. 
the  refolvable,  the  coloured  but  irrefolvable,  and  a  tin6lure  of 
the  milky  kind.  Now,  what  great  length  muft  be  required  to 
produce  thefe  effects  may  eafily  be  conceived  when,  in  all  pro- 
bability, our  whole  fyftem,  of  about  8co  ftars  in  diameter,  if 
it  were  feen  at  fuch  a  diftance  that  one  end  of  it  might  aliume- 
the  refolvable  nebulofity,  would  not,  at  the  other  end,  prefent 

\3S 


ConJiruBlm  of  the  Heavens.  2^7 

lis  with  the  irrefolvable,    much  lefs  with  the   colourlefs  and 
ir.ilky  fort  of  nebuJofities. 

ud  Perforated  Nebula,  or  Ring  of  Stars., 
Among  the  curiofities  of  the  heavens  (hould  be  placed  a 
nebula,  that  lias  a  regular,  concentric,  dark  Ipot  in  tiie  middle, 
and  is  probably  a  Ring  of  liars.  It  is  of  an  oval  {hape,  the 
iliorter  axis  being  to  the  longer  as  about  83  to  100  ;  fo  that,  if 
the  ftars  form  a  circle,  its  inclination  to  a  line  drawn  from  the 
lun  to  the  center  of  this  nebula  mufl  be  about  ^6  degrees.  The 
light  is  of  the  refolvable  kind,  and  in  the  northern  fide  three 
very  faint  ftars  may  be  feen,  as  alfo^  one  or  two  in  the  fouthern 
part.  The  vertices  of  the  longer  axis  feem  lefs  bright  and  not 
fo  well  defined  as  the  reft.  There  are  feveral  fmall  ftars  verv 
near,  but  none  that  feem  to  belong  to  it.  It  is  the  57th  of 
the  CQfinoiJjance  des  Temps,     Fig.  5.  is  a  reprefentation  of  it.. 

Planetary  Nebula. 

I  fhall  conclude  this  paper  with  an  account  of  a  few  hea- 
venly bodies,  that  from  their  lingular  appearance  leave  me  almofl; 
in  doubt  where  to  clafs  them. 

The  tirft  precedes  v  Aquarii  k^' ^^  in  time,  and  is  i^  more 
Horth.  Its  place,,  with  regard  to  a  fmall  ftar  Sept.  7,  1782, 
was,  Diftance  8^  j  3^^  S^^^'  '•>  ^^^  °"  account  of  the  low  iituation, 
and  other  unfavourable  circumftances,  the  meafure  cannot  be 
very  exaft.  Auguft  25,  1783,  Diftance  7'  5'^  ii-^\  veryexa^l^, 
and  to  my  fatisfatlion  ;  the  light  being  thrown  in  by  an  opaque- 
microicoplc-illumination  (^).     Sept.  20,  1783,    Pofition  41°  24' 

foutli 

{g)  It  may  be  of  ufe  to  explain  this  kin^  of  illumination  for  which  the  New- 
tonian refleftor  is  admirably  conftrudtetl.  On  the  fide  oppofite  the  eye-piece  an 
©pening  is  to  be  made  in  the  tube,  through  which  the  light  may  be  thrown  in,  fo 
a*  to  fall  on  fome  refleding  body,  or  concave  perforated  mirror,  within  the  eye- 

piece;,^ 


264  Mr ,  H  r,  R  scH  E  L  m  the 

fouth  preceding  the  fame  flar ;  very  exad,  and  by  the  fiime 
kind  of  illumination.  Od.,  17,  i7^'3,  Diftance  6' 55^'' 7'''^ ; 
a  iecond  mealure  6^  56^^  11'''''',  ns  exact  as  poflible.  Od.  23, 
i  783,  l^ofjtion  42^  57^ ;  a  fecond  meafure  42°  45^  ;  fingle  lens  ; 
power  71  ;  opaque  microfcopic-illumination.  Nov.  14,  1783, 
Diflance  7' 4'' 35""  Nov.  12,  1784,  Diflance  7^  22'^  35"^^ ; 
Pofition  38''  39^  Its  diameter  is  about  loor  15^''.  I  haveexa- 
miiicd  it  with  the  powers  of  71,  227,  278,  460,  and  932  ; 
nnd  it  follows  the  law^s  of  magnifying,  fo  that  its  body  is  no 
illuf  on  of  light.  It  is  a  little  oval,  and  in  the  7-feet  reflector 
pretty  well  defined,  but  not  fharp  on  the  edges.  In  the  20-feet, 
of  18,7  inch  aperture,  it  is  much  better  defined,  and  has  much 
of  a  planetary  appearance,  being  all  over  of  an  uniform  bright- 
nefs,  in  which  it  differs  from  nebulae  :  its  light  feems  however 
to  be  of  the  ftarry  nature,  which  fuffers  not  nearly  fo  much  as 
the  planetary  difks  are  known  to  do,  when  much  magnified. 

The  fecond  of  thefe  bodies  precedes  the  13th  of  Flam- 
steed's  Andromeda  about  1^6  in  time,  and  is  22^  more  fouth. 
It  has  a  round,  bright,  pretty  well  defined  planetary  difk  of 
about  12^^  diameter,  and  is  a  little  elliptical.  When  it  is  viewed 
with  a  7-feet  reflector,  or  other  inferior  inftruments,  it  is  not 
nearly  fo  well  defined  as  with  the  20-feet.  Its  lituation  with 
regard  to  a  pretty  confiderable  flar  is,  Diftance  (with  a  com- 
pound glafs  of  a  low  power)  f  51^^34^^'.  Pofition  i2°o'  f. 
preceding.     Diameter  taken  with  278,   14^''  42^^^. 

The  third  follows  B  (Fl.  44.)  Ophiuchi  4^,1  in  time,  and 
is  23^  more  north.  It  is  round,  tolerably  well  defined,  and 
pretty  bright  ;  its  diameter  is  about  30^^ 

piece,  that  may  throw  it  back  upon  the  wires.  By  this  means  none  of  the  direct 
rays  can  reach  the  eye,  and  thofe  few  which  are  reflefted  again  from  the  wires  do 
not  interfere  fenfibly  with  the  fainteft  objeds,  which  may  thus  be  fecn  undif- 
turbed.  \ 

The 


CojifruBwn  of  the  Heavens,  26  c 

The  fourth  follows  -/j  Sagittal  iy\i  in  time,  and  is  2' more 

north.     It  is  perfeclly  round,    pretty  bright,  and  pretty  well 

defined  ;  about  |  min.  in  diameter. 

The  fifth  follows  the  zift  Vulpeculaj   2.\i  in  time,  and  is 

1°   46^   more  north.     It   is   exa6llv    round,  of  an  equal  Ijoht 

•  J.  O 

throughout,  but  pretty  faint,  raid  about  i'  in  diameter. 

The  fixth  precedes  h  {Fi...  39,)  Cygni  8^,1   in  time,  and  is 

1°   26''  more  louth.     It   is   perfeftly    round,   and   of  an   equal 

light,  but  pretty  faint ;  its  diameter  is  neari",  and  the  edges 

are  pretty  well  defined. 

The  planetary  appearance  of  the  two  firfl  is  fo  remarkable, 
that  we  can  hardly  fuppoie  them  to  be  nebulae ;  their  light  is 
fo  uniform,  as  well  as  vivid,  the  diameters  fo  fmall  and  well 
defined,  as  to  make  it  almofl:  improbable  they  fhould  belong  to 
that  fpecies  of  bodies.  On  the  other  hand,  the  effe^Sl  of  dif- 
ferent powers  feems  to  be  much  againft  their  light's  being  of  a 
planetary  nature,  fince  it  preferves  its  brightnefs  nearly  in  the 
fame  manner  as  the  ftars  do  in  iimilar  trials.  If  we  would  fup- 
pofe  them  to  befingle  fliars  with  large  diameters  we  fhall  find  it 
difficult  to  account  for  their  not  being  brighter ;  unlefs  we 
fhould  admit  that  the  intrinfic  light  of  fome  ftars  may  be  very 
much  inferior  to  that  of  the  generality,  which  however  can 
hardly  be  imagined  to  extend  to  fuch  a  degree.  We  might 
fufpe6t  them  to  be  comets  about  their  aphelion,  if  the  bright- 
nefs as  well  as  magnitude  of  the  diameters  did  not  oppofe  this 
idea ;  fo  that  after  all,  we  can  hardly  find  any  hypotheiis  fo 
probable  as  that  of  their  being  Nebulic  ;  but  then  they  mufh 
coniift  of  ftars  that  are  comprefled  and  accumulated  in  the 
higheft  degree.  If  it  were  not  perhaps  too  hazardous  to  purfue 
a  former  lurmife  of  a  renewal  in  what  I  figuratively  called  the 
Laboratories  of  the  univerfe,  the  f!:ars  forming  thefe  extraordi- 
nary  nebulae,  by  fome  decay  or  wafte  of  nature,  being  no  longer 
Vol.  LXXV.  U  m  fit 


2,66        Mr.  Herschel  on  the  Conjlruciion  of  the  Heavens. 

fit  for  their  former  purpofes,  and  having  their  projedile  forces^ 
if  any  i'uch  they  had,  retarded  in  each  others  atmolphere,  may 
rufh  at  Lift  together,  and  either  in  fuccefiion,  or  by  one  general 
tremendous  iliock,  unite  itito  a  new  body.  Perhaps  the  ex- 
traordinary and  iudden  biaze  of  a  new  ftar  in  Cailiopea's  chair, 
in  1572,  miglit  pofiibly  be  of  fuch  a  nature.  Butleil  I  Ihould 
be  led  too  flir  from  the  path  of  obfervation,  to  which  I  am 
refolved  to  Umit  mylelf,  1  fliall  only  point  out  a  confiderable 
ufe  that  may  l>€  made  of  thele  curious  bodies.  If  a  little  atten- 
tion  to  them  ihould  prove  that,  iiavlng  no  annual  parallax,  they 
belong  moft  probably  to  the  clafs  of  nebulae,  they  may  then 
be  expe^^ed  to  keep  their  fituation  better  than  any  one  of  the 
ftars  belonging  to  our  lyftem,  on  account  of  their  being  pro- 
bably at  a  very  great  diflance.  Now  to  have  a  fixed  point 
fomewhere  in  the  heavens,  to  which  the  motions  of  the  reft 
may  be  referred,  is  certainly  of  confiderable  confequence  ia 
Aflronomy  ;  and  both  thefe  bodies  are  bright  and  fmall  enough, 
to  anfwer  that  end  (/6). 

Datchet  fiear  Windfor,  W.    HERSCHEI.. 

January  i,    1785. 

{h)  Having  found  two  more  of  thefe  curious  objefts,  I  add  the  place  of  them 
here,  in  hopes  that  thofe  who  have  fixed  inllruments  may  be  induced  to  take  an 
early  opportunity  of  obferviug  them  carefully. 

Feb.  I,  1785.  A  very  bright,,  planetary  nebula,  about  half  a  minute  in  diame- 
ter, but  the  edges  are  not  very  well  defined.  It  is  perffdiy  round,  or  peihaps  a 
very  little  elliptical,  and  all  over  of  an  xuiiform  brightnt  Is  :  with  higher  powers 
it  becomes  proportionally  magnified.  It  follows  y  Krrdani  16'  16"  in  time,  and 
5S  49'  more  north  than  that  liar. 

Feb.  7,  1785.  A  beautiful,  very  brilliant  globe  of  light;  a  little  hazy  on  the 
edges,  but  the  hazinefs  goes  off  very  fuddenly,  fo  as  not  to  exceed  the  20th  part 
of  the  diameter,  which  I  fuppofe  to  be  from  30  to  40".  It  is  round,  or  perhaps 
a  very  little  elliptical,  and  all  over  of  an  uniform  brightnefs  :  I  fuppofe  the  intenfity 
of  its  light  to  be  equal  to  that  of  a  ilar  of  the  ninth  magnitude.  It  precedes  the 
third  b  (Fl.  6.)  Crateris  28'  36''  in  time,  and  is  i"  25'  more  north  tlian  that  flar. 


n:r/.    '  fn:':,    TY  /  AAf     T.il.  till    ,>  itlO. 


■^"/■:i. 


'  ^'y  /■ 


■■*■*■.■.*.:.  .*•:?:t^•;>/v.^^\!%*^..*.    *.  — 


[     ^6?     ] 


XIII.  Remarks  on  Jpec'ific  Gravities  taken  at  different  Degrees  of 
Heat,  and  an  eafy  Method  of  reducing  them  to  a  common  Stan- 
dard.    By  Richard  Kirwan,  Efq,  F.  R.  S. 


Read  February  17,   1785. 

« 

THAT  a  comparative  view  of  the  weights  of  equal  volumes 
of  water  and  all  other  fubftaiiccs  is  highly  uleful  on 
many  occafions,  is  too  well  known  to  require  any  proof;  but 
that  a  principal  ule  refaiting  from  this  compariion,  when  pro- 
perly made,  is  unattainable  by  a  perulal  of  the  common  tables, 
I  fhall  here  endeavour  to  ihew,  and  at  the  fame  time  point 
out  a  remedy  for  this  defeft. 

One  capital  advantage  derivable  from  a  table  of  fpecific  gra- 
vities, is  the  knowledge  of  the  abfolute  weight  of  any  lolid 
meafure  of  the  fubftances  therein  contained,  or  that  of  the  folid 
meafure  of  a  given  weight  of  thofe  fubftances,  a  cubic  foot  of 
water  being  luppofed  to  weigh  1000  ounces  avoirdupois,  and 
confequently  a  cubic  inch  of  water  weighing  253,182  grains. 
But  the  authors  who  havedifcovered  this  equation  of  weight  and 
meafure,  and  all  thofe  who  have  fince  treated  this  fubjec^l,  have 
neglected  to  inform  us  of  the  temperature  at  which  this  agree- 
ment takes  place  ;  yet  that  it  cannot  take  place  in  all  tempera- 
tures is  evident  from  the  experiments  of  Dr.  Halley  and 
others,  who  have  found,  that  from  a  few  degrees  above  the 
freezing  to  the  boiling  point,  water  is  dilated  about  ^'-^  of  its 
bulk;  and,  confequently,  if  1000  ounces  at  the  freezing  point 
be  equal  to  one  cubic  foot,  they  mud  be  equal   at  the   boiling 

M  m  2  poin 


I 


268  Mr.  Kir  WAN's  Remarks  on  fpecific  Gravities 

point  to  oiij  cubic  foot  and  66,46  cubic  inches.  And  if  the 
dilatations  are  proportional  to  the  degrees  of  heat  throughout 
the  fcale,  there  mufl  be  an  augmentation  of  3,136  cubic  inches 
per  cubic  foot,  produced  by  every  10  degrees  of  heat.  Both 
thefe  points  remain,  therefore,  to  be  determined  ;  firft,  at  what 
temperature  a  cubic  foot  of  water  weighs  exactly  1000  ounces 
avoirdupois  ;  and,2dly,  whether  the  dilatations  produced  by  fuc- 
ceffive  degrees  of  heat  are  proportional  to  the  degrees  that  pro- 
duce them.  This  laft  point  has  indeed  been  handled  by  others, 
but  with  different  views ;  and  their  determinations  are  not  eafily 
applicable  to  the  prefent  queftion. 

To  examine  this  matter  experimentally,  I  ordered  a  hollow 
tinned  iron  cone  to  be  made,  of  four  inches  diameter  in  the 
bafe,  one-tenth  of  an  inch  diameter  in  the  lummit  infide,  and 
10  inches  perpendicular  height,  Whofe  folid  contents  fliould  be 
42,961  cubic  inches,  but  by  a  flight  diminution  of  the  dia- 
meter, and  a  protuberance  ariiing  from  the  foldering,  I  found 
it  to  contain,  in  the  temperature  of  62°,  but  42,731  cubic 
inches,  according  to  the  eftimation  of  1000  ounces  to  the 
cubic  foot  ;  and  having  filled  it  by  immerfion  in  boihng  water, 
and  taken  it  up  at  different  degrees  of  heat,  and  weighed  it 
when  cold,  I  found  its  contents  as  exprefled  in  the  following 
table  ;  the  firft  column  of  which  fliews  the  degrees  of  heat  at 
which  it  was  taken  up  ;  the  fecond,  the  weight  of  the  water 
contained  in  it ;  the  third,  the  diminution  of  weight  occafioned 
by  thofe  degrees  of  heat  j  the  fourth,  the  fum  of  the  diminu- 
tions of  weight  in  the  cubic  foot,  by  the  preceding  degrees  of 
heat ;  the  fifth  fhews  the  weight  of  a  cubic  inch  of  water  in 
each  of  thofe  degrees  of  heat;  and  the  fixth,  the  augmentation 
of  bulk  in  the  cubic  foot  by  every  20°  of  heat.  The  horizontal 
lines,  marked  thus  ^j  I  have  added  from  the  experiments  of  Mr, 

z  •  BladHj 


at  different  Degrees  of  Heat.  269 

Bladh,  ill  the  Memoirs  of  the  Academy  of  Stockhohn  for  the 
year  1776,  whofe  determinations,  as  far  as  they  reached,  agreed 
very  nearly  with  mine.  The  water  I  ufed  was  common  water 
well  boiled  and  filtered.  The  experiments  were  for  the  moft 
part  three  times  repeated,  and  the  difference  in  each  trial 
amounted  to  a  very  few  grains. 


I. 

11. 

III. 

IV. 

V. 

VI. 

Contents  of 

Dimin, 

Sum  of 

Weight  of 

Increafe 

Degrees 

the  cone  in 

in 

dim.  in  a 

a  cubic 

in  cubic 

grains. 

grains. 

cubic  foot. 

inch. 

inches. 

Grs. 

212 

10418,75 

29'5 

16589 

243,8 

4,892 

202 

10448,25 

77,5 

15354 

244,51 

12,818 

182 

10525,75 

71,75 

J  2  133 

246,33 

^^^S33 

162 

10596,00 

62,60 

9171 

247,97 

10^209 

142 

10658,60 

56,15 

6602 

249'43 

9rio3 

122 

10714,75 

49,00 

4310 

250,75 

7,920 

102 

10763,75 

35,5 

2226 

25^,89 

5,7 

82 

10799,25 

19,5 

788 

252,72 

3,' 20 

*75 
*7o 

252,8 
252,97 

—    —    — 

■^        ta«i         >»■ 

*66 

253,06 

_    _    _ 

M. 

62 

10818,75 

0 

0 

253,182 

0 

Total  increafe  of 

^^6 

253,3 

_    —    — 

bulk  from  62°  to 

*50 

Increafe 

Increafe 

253'46 

2i2°=65,327cu- 
bic  inches. 

'"' 

Dec  re  a  fe 

Total  from  36'^  to 

42 

10830,75 

12 

485,3 

253,463 

ir936 

212  =  67,327  cu- 

^•3^'S 

253,5 

0,064 

bic  inches. 

Hence  wx  fee,  that  a  cubic  foot  of  water  weighs  4<?5,3  grains 
more  at  42°  than  at  62',  and  confequently  is  equal  to  1001,109 
avoirdupois  ounces,  and  in  the  temperature  of  82^  it  weighs  lefs 
than  at  62°  by  788,5  grains,  and  therefore  is  equal  to  998,198 
ounces.  At  the  boihng  point  it  wants  16589  grains,  or  ^y,()iS 
ounces  of  the  weight  it  poflefles  at  62°,  and  confequently 
weighs  but  962,085  ounces,  &e. 

In 


2  70  Mr.  Kir  WAN's  Reworks  onfpec'ific  Gravities 

'  In  this  calcuiatiou  I  take  no  account  of  the  difference  arlfing 
from  the  expanfion  of  the  veffel,  It  being  only  0,067  of  an 
hich  at  the  boiling  point;  for,  according  to  Bouguer,  iron  is 
dilated  0,00055  of  its  bulk  from  the  freezing  to  the  boiling 
point;  confequentlj  42,961  cubic  inches  gain  only  0,067  ^^  '^^ 
inch,  augmenting  the  diameter  and  perpendicular  height  of 
this  fruftum  of  a -cone  at  the  boiling  point  in  that  proportion. 

ilcnce  alio  we  fee,  that  the  expanfions  of  water  are  not  pro^ 
portional  to  the  degrees  of  heat ;  for  by  20  degrees  of  heat  from 
62''  to  82"  a  cubic  foot  of  water  is  dilated  only^,!  2  inches,  but  by 
the  next  20  degrees  of  heat,  that  is,  from  82°  to  102°,  it  is 
expanded  ^^']  inches,  &c. 

Mr.  Bladh  found  the  volume  of  wat?er  at  32°  to  be  equal 
to  that  at  ^'^^(y ;  but  that  this  irregular  expanfion  ceafed  at  36-6, 
and,  according  to  Mr.  De  Luc  (who  firft  difcovered  it)  at  43°. 

As  the  expanfion  of  liquids  by  equal  degrees  of  heat  is  much 
greater  than  that  of  foiids,  it  happens,  that  the  fpecific  gravi- 
ties of  the  fame  folid  taken  at  different  temperatures  will  be 
different ;  and.,  what  appears  more  extraordinary,  the  fame  folid 
will  appear  fpecitically  heavier  in  higher  than  in  lower  tempera- 
tures ;  for  the  fame  volume  of  water  being  lighter  in  higher 
than  ill  lower  temperatures,  the  folid  will  lofe  lefs  of  its  weight 
in  it  in  the  former  than  in  the  latter  cafe  :  this  mlilake  we 
may  remedy  by  infpe6llng  the  fifth  column  of  the  foregoing 
table  and  the  following  analogy.:  as  the  weight  of  a  cubic  inch 
of  water  at  the  temperature  of  62°  is  to  the  weight  of  a  cubic 
inch  of  water  at  n  degrees  of  temperature,  fo  is  the  fpecific 
gravity  found  at  n  degrees  of  temperature  to  that  which  will 
be  found  at  62°. 

Thus,  if  1000   grains  of  iron  be  weighed  in  water  of  the 
•temperature  of  62°,  and  it   lofes  therein   i 3,^33  grains,  if  the 

fame 


at  diftrent  Degrees  of  IJeat.  271 

fame  piece  of  iron  be  weighed  in  water  of  the  temperature  of 
75°,  it  will  lofe  but  13,313  grains;  for  the  lofies  of  weight 
will  be  as  the  weights  of  equal  volumes  of  water  at  thofe  tem- 
peratures, which,  as  we  have  feen,  are  as  253, 1 8  to  252,8  ;  there- 
fore, its  fpecific  gravity  in  water  of  the  temperature  of  62° 
•will  be  7,49;  and  in  water  of  the  temperature  of  75°.  7,51 1  ; 
but  we  may  corredl  this  by  the  above  analogy,  for 
^  253,8  .  252,18  ::  7,51  I  .  7,49. 

By  this  means  we  obtain  the  advantage  of  difcovering  the 
true  weight  of  a  cubic  foot  of  any  fubftance  whole  fpecific  gra- 
vity is  known,  which  it  is  now  plain  cannot  be  know^n  when 
bodies  are  hydroftatically  weighed  at  any  temperature  a  few 
degrees  above  or  below  62%  without  fuch  redudion,  or  fub-^ 
trading  the  quantities  in  the  fourth  column. 

This  method  is  equally  applicable,  and  with  equal  neceffity, 
to  other  means  of  finding  fpecific  gravities,  as  areometers,  the 
comparifon  of  the  weights  of  equal  meafures  of  liquids,  the 
different  lofles  of  weight  of  the  fame  folid,  when  weighed  in 
different  liquids,  &c.  In  all  which  cafes  the  weight  of  water 
at  62°,  or  the  lofs  of  weight  of  a  folid  in  water  at  62%  (hould 
be  found  by  the  above  analogy. 

Dr.  Hales  and  fome  others  have  eftimated  the  weight  of  a 
cubic  inch  of  water  at  254  grains,  which  is  an  evident  miftake, 
as  it  is  true  in  no  degree  of  temperature,  and  produces  an  error 
of  more  than  three  ounces  in  the  cubic  foot. 


t   272   ] 


XIV.  UkSirical  'Experiments  made  In  order  to  a/certain  the  non- 
conduct ing  Power  of  a  perfeB  Vacuum^  &c.  By  Mr.  Wil- 
liam Morgan ;  communicated  by  the  Rev,  Richard  Price, 
LL.D.  F.R,S. 


Read  February  24,  IJ^S- 


■^HE  iion-condu£ling  power  of  a  perfect  vacuum  is  a  fade 
in  eledlricity  which  has  been  much  controverted  among 
philofophers.  The  experiments  made  by  Mr.  Walsh,  F.R.S.  in 
the  double  barometer  tube  clearly  demon ftrated  the  impermeabi- 
lity of  the  electric  I/ght  through  a  vacuum  ;  nor  was  it,  1  think, 
precipitate  to  conclude  from  them  the  impermeabihty  of  the 
eleOincJIuid  itfelf.  But  this  conclufion  has  not  been  univerfally 
admitted,  and  the  following  experiments  were  made  with  the 
view  of  determining  its  truth  or  fallacy.  When  I  firfl  attended 
to  the  fubjedl,  I  was  not  aware  that  any  other  attempts  had 
been  made  beiides  thofe  of  Mr.  Walsh  ;  and  though  I  have 
fuice  found  myfelf  to  have  been  in  part  anticipated  in  one  of 
my  experiments,  it  may  not  perhaps  be  improper  to  give  feme 
account  of  them,  not  only  as  they  are  an  additional  teftimony 
in  fupport  of  this  fad',  but  as  they  led  to  the  obfervation  of 
lome  phaenomena  which  appear  to  be  new  and  interelling. 

A  mercurial  gage  B  (fee  tab.  IX.  iig.  i.)  about  15  inches 
long,  carefully  and  accurately  boiled  till  every  particle  of  air 
was  expelled  from  the  iniide,  was  coated  with  tin- foil  five 
anches  down  from  its  fealed  end  (A),  and  being  inverted  into 

mercury 


Mr.  Morgan's  Experiments,  &c.  273 

'tnercury  through  a  perforation  (D)  In  the  brafs  cnp  (E)  which 
■covered  the  mouth  of  the  cill:ern  (H),  the  whole  was  cemented 
together,  and  the  air  was  exhaufted  from  the  infide  of  the 
cillern  through  2.  valve  (C)  in  the  brafs  cap  (E)  jufl:  mentioned, 
w^hich  producing  a  perfect  vacuum  in  the  gage  (B)  afforded  aa 
-Inlh-ument  pecuharly  well  adapted  for  experiments  of  this 
kind.  Things  being  thus  adjufted  (a  fmall  wire  (F)  having 
been  previoully  fixed  on  the  intide  of  the  ciftern  to  form  a  com- 
munication between  the  brals  cap  (E)  and  the  mercury  (G) 
into  which  the  gage  was  inverted)  tlie  coated  end  (A)  was  ap- 
plied to  the  conductor  of  an  electrical  machine,  and  notvvith- 
ftan ding  every  effort,  neither  the  Inialieft  ray  of  light,  nor  the 
flighteft  charge,  could  ever  be  procured  in  this  exhaufted  gage. 
I  need  not  obferve,  that  if  the  vacuum  on  its  infide  had  been  a 
conductor  of  electricity,  the  latter  at  leall:  muff  have  taken 
place ,  for  it  is  well  known  (and  I  have  myfelf  often  made  the 
experiment)  that  if  a  glafs  tube  be  exhaufted  by  an  air-pump, 
and  .coated  on  the  outfide,  both  light  and  a  charge  may  very 
readily  be  procured.  If  the  mercury  in  the  gage  be  imperfectly 
boiled,  the  experiment  will  not  fucceed  ;  but  the  colour  of  the 
electric  light,  wdiich,  in  air  rarefied  by  an  exhaufter,  is  always 
violet  or  purple,  appears  in  this  cafe  of  a  beautiful  green,  and, 
what  is  very  curious,  the  degree  of  the  air's  rarefaction  may  be 
nearly  determined  by  this  means  ;  for  I  have  known  inftances, 
during  the  courfe  of  thefe  experiments,  where  a  fmall  particle 
of  air  having  found  its  way  into  the  tube  (B),  the  eleCtric 
light  became  vjfible,  and  as  ufual  of  a  green  colour ;  but  the 
cliarge  being  often  repeated,  the  gage  has  at  length  crack^^^f  ■•' 
its  fealed  end,  and  in  confequence  the  external  air,  by  being 
admitted  into  the  infide,  has  gradually  produced  a  change  in 
the  eleCtric  light  from  green  to  blue,  from  blue  to  indigo,  and 
Vql..  LXXV.  N  n  io 


2*-4  Mr'.  Morgan's  Experiments  to  a/certain  the 

fo  on  to  violet  and  purple,  tiii  the  medium  has  at  lafl  become  fb 
denfe  as  no  longer  to  be  a  condu6tor  of  electricity.     I  think 
there  can  be   little  doubt  from  the  above  experiments  of  the 
non-conduvfting  power  of  a  perfefl  vacuum ;  and   this   fa61t:  is 
flili  more  ilirongly  confirmed  by  the  phenomena  which  appear 
upon   the  admiflion  of  a  very  minute   particle  of  air  into  the 
iniide  of  the  gage.     In  this  cafe   the  whole  becomes  imme- 
diately luminous  upon   the   flightefl   application  of  electricity, 
and  a  charge  takes  place,  which   continues  to  grow  more  and 
more  powerful   in  proportion   as   frelh  air  is  admitted,   till  the 
deniity  of  the   condu6ling   medium    arrives  at  its  maximum, 
which  it  always  does  when  the  colour  of  the  electric'  light  is 
indigo  or  violet.     Under  thefe   circumftances  the  charge  may 
be  fo  far  increafed  as  frequently  to  break  the  glafs.     In  fome 
tubes,  which  have  not  been  completely  boiled,  I  have  obferved, 
that  they  will  not  condudt  the  eledtric  fluid  when  the  mercury  is 
fallen  very  low  in  them,  yet  upon  letting  in  air  into  the  ciftern 
(H),  fo  that   the  mercury  fliall  rife  in  the  gage  (B),  the  elec- 
tric fluid,  which  was  before  latent  in  the  iniide,  fhall  now  be- 
come viiible,  and  as  the  mercury  continues  to  rife,  and  of  con- 
fequence  the  medium  is  rendered  lefs  rare,  the  light  fhall  grow 
more  and  more  vifible,  and  the  gage  Ihall  at  laft  be  charged, 
notwithftanding  it  has  not  been  near  an  eleilrical  machine  for 
two  or  three  days.     This  feems  to  prove,  that  there  is  a  limit 
even  in  the  rarefaction  of  air,  which  fets  bounds  to  its  con- 
ducting power  ;  or,  in  other  words,  that  the  particles  of  air  may 
be  fo  far  feparated  from  each  other  as  no  longer  to  be  able  to 
tranfmit  the  eleClric  fluid ;  that  if  they  are  brought  within  a 
certain  diflance  of  each  other,their  conducing  power  begins,  and 
continually  increafes  till  their  approach  alfo  arrives  at  its  limit, 
when  the  particles  again  become  fo  near  as  to  relifl  the  pafTage 
4  of 


noU'COfiJutf'ing  Fo'ive*'  of  a  perjcct  Vacuum^  275 

Qii  the  fluid  entirely,  without  employing  violence,  which  is 
the  cafe  iii  common  and  condenied  air,  but  more  particularly 
in  the  latter.  Thefe  experiments,  however,  belong  to  another 
fubject,  and  may  poflibly  be  communicated  at  fome  future 
time. 

It  is  furprifing  to  obferve,  how  readily  nn  exhaufled  tube  is 
charged  with  elecfhricity.  By  placing  it  at  ten  or  twelve  inches 
from  the  condudlor  the  light  may  be  feen  pervading  itsin{ide,and 
as  ftrong  a  charge  may  iometimes  be  procured  as  if  it  Vv'-ere  in 
conta6l  with  the  conductor:  nor  does  it  iignify  how  narrovv^the 
bore  of  the  glafs  maybe;  for  even  a  thermometer  tube,  having 
the  minutefl  perforation  poffible,  will  charge  with  the  utmoil: 
facility;  and  in  this  experiment  the  phasnomena  are  peculiarly 
beautiful. 

Let  one  end  of  a  thermometer  tube  be  fealed  hermetically. 
Let  the  other  end  be  cemented  into  a  brafs  cap  with  a  valve, 
or  into  a  brafs  cock,  fo  that  it  may  be  fitted  to  the  plate  of  an 
air-pump.  When  it  is  exhaufted,  let  the  fealed  end  be  applied 
to  the  conductor  of  an  electrical  machine,  while  the  other  end 
is  either  held  in  the  hand  or  connected  to  the  floor.  Upon  the 
flighteft  excitation  the  ele6tric  fluid  will  accumulate  at  the  fealed 
end,  and  be  difcharged  through  the  infide  in  the  form  of  a 
fpark,  and  this  accumulation  and  difcharge  may  be  inceffantly 
repeated  till  the  tube  is  broken.  By  this  means  I  have  had  a 
fpark  42  inches  long,  and,  had  I  been  provided  with  a  proper  tube, 
1  do  not  doubt  but  that  I  might  have  had  a  fpark  of  four  times 
that  length.  If,  inftead  of  the  fealed  end,  a  bulb  be  blown  at  that 
extremity  of  the  tube,  the  ele6tric  light  will  fill  the  whole  of 
that  bulb,  and  then  pafs  through  the  tube  in  the  form  of  a 
brilliant  fpark,  as  in  the  foregoing  experiment ;  but  in  this  cafe 
1  have  feldom  been  able  to  repeat  the  trials  above  three  or  four 

N  n  2  times 


276  Mr.  Morgan's  Exferimenis  to  afiertam  th^ 

times  before  the  charge  has  made  a  fmall  perforation  in  the; 
bulb.  If  again  a  thermometer  filled  with  mercury  be  inverted, 
into  a  ciftern,  and  the  air  exhaufted  in  the  manner  I  have  de- 
fcribed  for  making  the  experiment  with  the  gage,  a  Torricellian, 
vacuum  will  be  produced;  and  now  the  electric  light  in  the. 
bulb,  asw^ell  as  the  fpark  in  the  tube,  will  be  of  a  vivid  green; 
but  the  bulb  will  not  bear  a  frequent  repetition  of  charges  be- 
fore it  is  perforated  in  like  manner  as  when  it  has  been  ex- 
haufted  by  an.  air-pump.  It  can  hardly  be  neceflary  to  obferve, 
that  in  thefe  cafes  the  ele6lric  fluid  affumes  the  appearance  of  a 
fpark*,  from  the  narrownefs  of  the  paflage  through  which  it 
forces  its  way.  If  a  tube,  jj-O  inches  long,  be  fixed  into  a  globe 
8  or  9  inches  in  diameter,  and  the  whole  be  exhaulled,  the  eledlric 
fluid,  after  pafling  in  the  form  of  a  brilliant  fpark  throughout: 
the  length  of  the  tube,  will,  when  it  gets  into  the  inlide  of  the 
globe,  expand  itfelf  in  all  diredlions,  entirely  filling  it  wuth  a 
violet  and  purple  light,  and  exhibiting  a  ftriking  inftance  of  the 
vafl  elafticity  of  the  eledric  fluid., 

I  cannot  conclude  this  paper  without  acknowledging  my  obli- 
gations to  the  ingenious  Mr.  Brook,  of  Norwich,  who,  by  com- 
municating to  me  his  method  of  boiling  mercury,  has  been  the 
chief  caufe  of  my  fuccefs  in  thefe  experiments  f.     I  have  lately 

learned  I 

*  By  cementing  the  firing  of  a  guittar  into  one  end  oF  a  thermometer  tube,  a 
f]}ark  may  be  obtained  as  well  as  if  the  tube  had  been  fealed  hermetically. 

t  Mr.  Brook's  method  of  making  mercurial  gages  is  nearly  as  follows.  Let  a 
glafs  tube  L  (fee  fig.  2.)^  fealed  hermetically  atone  end^  be  bent  into  a  right- 
angle  within  two  or  three  inches  of  the  other  end.  At  the  diilance  of  about  an  inch 
or  lefs  from  the  angle  let  a  bulb  (K),  of  about  \  of  an  inch  in  diameter,  be  blown 
ia  the  curved  end,  and  let  the  reroainder  of  this  part  of  the  tube  be  drawn  out  (I) 


mn-comhcihig  Power  of  a  perfeci  Vacuum.  z^--] 

learned  from  him,  that  he  has  alfo  afcertained  the  non-conc!u6ting 
power  of  a  perfedl  vacuum  ;:  but  what  fteps  he  took  for  that  pur- 
pofe  I  know  not.  Of  his  accuracy,  however,  I  am  fo  well  con- 
vinced,that  hadlnever  made  an  experiment  myfelfj  fiiould,upoii 
his  teftimony  alone,  have  been  equally  afllired  of  the  facO:.  To 
mofl:  of  the  preceding  experiments  Dr.  Price,  Mr.  Lane,  and 
fome  others  of  my  friends,  have  been  eye-witnelles,  and  I  be- 
lieve that  they  were  as  thoroughly  fatisfied.  as  myfelf  with  the 
refults  of  them.  I  muft  beg  leave  to  obferve  to  thofe  who  wiflT 
to  repeat  them,  that  the  firft  experiment  requires  fome  nicety, 
and  no  inconliderable  degree  of  labour  and  patience.  I  have 
boiled  many  gages  for  feveral  hours  together  without  fuccefs,. 

fo  as  to  be  fufficiently  long  to  take  hold  of,  when  the  mercury  is  boiling.     The 
bulb  (K)  is  defigned  as  a  receptacle  for  the  mercury,  to  prevent  its  boiling  over,, 
and  the  bent  figure  of  the  tube  is  adapted  for  its  inverfion  into  the  ciftern  ;  for  by 
breaking  off  the    tube   at    (M)   within  |-  or   |  of  an  inch  of  the  angle,  the  open 
end  of  the  gage  may  be  held  perpendicular   to    the  horizon-when  it  is  dipped  into 
the  mercury  in   the  ciftem,   wiihuut  obliging  us  to  bring  our  finger,   or  any  other 
fubftance,  into  conta£l  with  the  mercury  in  the  gage,.which  never  fails  to  render  the 
inftrument  imperfeft.     It  is  necelTary  to  obferve,,  that  if  the  tube  be  fourteeii 
or  fifteen  inches  long,  I  have  never  been  able  to  boil   it  effedually  for  the  experi- 
ments mentioned  in  this  paper  in  lefs   than  three  or  four  hours,  although  Mr. 
Brook  feems  to  prefcribe  a  m.uch  fliorter  time  for  the  purpofe ;  nor  will  it  even 
then  fucceed,  xinlefs  the  greateft  attention  be  paid  that  no   bubbles  of  air   lurk 
behind,  which  to  my  own  mortification  I  have  frequently  found  to  have  been  the 
cafe  ;  but  experience  has  at  length  taught  me  to  guard  pretty  well  againft  this 
difappointment,  particularly  by  taking  care  that  the  tube  be  completely  dry  before 
the  mercury  is  put  into  it ;  for  if  this  caution  be  not  obferved,  the  inftrument  can 
never  be  made  perfeft.  There  is,  however,  one  evil  which  I  have  not  yet  been  able  to 
remedy  ;  and  that  is,  the  introduftion  of  air  into  the  gage,  owing  to  the  unboiled 
mercury  in  the  ciftern  ;   for  when  the  gage  has  been  a  few  times  exhaufted,  the  mer- 
cury which  originally  filled  it  becomes  mixed  with  that  into  which  it  is  inverted,  and 
ii^confequence  the  vacimm  is  rendered  lefs  and  lefs  perfect,  till  at  laft  the  inftru- 
ment is  entirely  fpoiled.     I  have  juft  conftrudled  a  gage  fo  as  to  be  able  to  boil  the, 
mercury  in  the  ciilern,.  but  have  not  yet  afcertained  its  fuccefs,. 

and' 


•  2  ; 8  Mr.  l\\ u II G  A  N ' s  Experiments,  Sec, 

'<\nd  was  for  fome  time  difpofed  to  believe  the  contrary  of  what 
I  am  now  convinced  to  be  the  truth.  Indeed,  if  we  reafon 
fi  priori,  I  think  we  cannot  luppofe  a  perfect  vacuum  to  be  a 
perfect  condudor  without  fuppofing  an  abfurdity:  for  if  this 
were  the  caie,  either  our  atmofphere  mufl:  have  long  ago  been 
deprived  of  all  its  ele6tric  fluid  by  being  every  where  lur- 
3'ounded  by  a  boundlefs  conductor,  or  this  fluid  mufl:  pervade 
every  part  of  infinite  fpace,  and  confequently  there  can  be  no 
Ihch  thing  as  a  perfe6l  vacuum  in  the  univerfe.  If,  on  the 
contrary,  the  truth  of  the  preceding  experiments  be  admitted, 
it  will  follow,  that  the  conducting  power  of  our  atmofphere  in- 
creafes  only  to  a  certain  height,  beyond  which  this  power  be- 
gins to  diminifli,  till  at  lafl:  it  entirely  vaniflies ;  but  in  what 
part  of  the  upper  regions  of  the  air  thefe  limits  are  placed,  I 
will  not  prefume  to  determine.  It  would  not,  perhaps,  have 
been  difficult  to  have  applied  the  refults  of  fome  of  thefe  ex- 
periments to  the  explr.nation  of  meteors,  which  are  probably 
owing  to  an  accumulation  of  eledtricity.  It  is  not,  however, 
my  prefent  defign  to  give  loofe  to  my  imagination.  I  am  fen- 
fible,  that  by  indulging  it  too  freely,  much  harm  is  done  to 
real  knowledge ;  and  therefore,  that  one  fa£t  in  philofophy  well 
afcertained  is  more  to  be  valued  than  whole  volumes  of  fpecu- 
lative  hypothefes. 

Chatham-Place,  Feb.  12,  1785. 


y 


ri„/..,r„„„  ;;./j.x.\TU,  1.V278. 


^■' 


'.>W.  2. 


[     '-19     ] 


XV.   'Experiments  cind  Ohfervatlons  relating  to  Air  and  Water, 
By  the  Rev.  Jofeph  Prieillej,  LL.D.  F.R.S, 


Read  February  24,   1785. 

EVER  fiiice  the  difcovery  of  the  diminution  of  refpirable 
air  in   thofe  procelTes  which  are  generally  called  phlogijiic^ 
it  has   been  a  great  object  with  philofophers  to  find  what  be- 
comes of  the  air  which  difappears  in  them.     Among  others,  I 
have  made  and  publifhed  a  variety  of  experiments  with  that 
view;  but   though   by   this  means  fome  farther  progrefs  was 
made  in  the  philofophy  of  air,  and  confequently  our  know- 
ledge of  the  principles,  or  conflituent  parts,  of  natural  fub- 
jftances  was  extended,  I  did  not  by  any  means  fucceed  to  my 
fatisfadion   with  refpe£l  to   the  immediate  obje£l  of  my   re- 
fearches.     Others,  however,  v^^ere  more  fuccefsful,  and  their 
fuccefs  has  at   length   enabled  me   to  refume  my  experiments 
with  more  advantage  ;  by  which  means  I  have  been  led  both  to 
confirm   their  conclufions,    and,    by  diverfifying   the    experi- 
ments, to  throw  confiderable  light  upon  various  other  chemical 
procefles.     The  refult  of  thefe  obfervations  I  fhall  lay  before 
the  Society,  with  as  much  brevity  and  diftindtnefs  as  I  can. 

Li  the  experiments  of  which  I  fhall  now  give  an  account, 
I  was  principally  guided  by  a  view  to  the  opinions  which  have 
lately  been  advanced  by  Mr.  Cavendish,  Mr.  Watt,  and 
M.Lavoisier.  Mr.  Cavendish  was  of  opinion,  that  when 
<?/r  is  deeompofed,  water  only  is  produced;  and  Mr.  Watt 

concluded 


2?o  Dr.  Priestley's  Experimetits  andOhfervatlons 
concluded  from  fome  experiments,  of  which  I  gave  an  account 
to  the  Society,  and  ahb  from  fome  obfervations  of  his  own, 
that  water  confifts  of  dephlogifticated  and  inflammable  air, 
in  which  Mr.  Cavendish  and  M.  Lavoisier  concur  with 
him;  but  Mr.  Lavoisier  is  well  known  to  maintain,  that 
there  is  no  fuch  tiling  as  what  has  been  called  phiogi/Io?i,  affirm- 
ing inflammable  air  to  be  nothing  elfe  but  one  of  the  elements 
of  condituent  parts  of  water.  In  the  following  experiments  I 
alfo  had  a  particular  view  to  a  conclufion  which  1  had  drawn 
from  thofe  experiments,  of  which  an  account  is  given  in  my 
laft  communications  to  the  Royal  Society  j  vi%,  that  inflam- 
mable air  is  pure  phlogiilon  in  the  form  of  air,  at  lead  with 
the  element  of  heat ;  and  that  fixed  ah*  confifls  of  dephlogifti- 
cated  and  inflammable  air;  both  which  do6lrines  had  been  firft 
advanced  by  Mr.  Kir  wan,  before  I  had  made  the  experiments 
which  I  then  thought  clearly  proved  them. 

^uch  were  the  hypothefes  to  which  I  had  a  view  when  I 
began  the  following  courfe  of  experiments,  which  I  hope  will 
be  an  admonition  to  myfelf,  as  w^U  as  to  others,  to  adhere  as 
jigoroufly  as  poffible  to  aSlual  obfervations,  and  to  be  extremely 
careful  not  to  overlook  any  circumftance  that  may  poffibly  con- 
tribute to  any  particular  refult.  I  fhall  have  occafion  to  notice 
my  own  miilakes  with  refpe£l  to  co?icluJto?is,  though  all  the 
fiiBs  were  ftri6lly  as  I  have  reprefented  them.  But  whilfl  phi- 
lofophers  are  faithful  narrators  of  what  they  obferve,  no  perfoii 
can  juflly  complain  of  being  milled  by  them;  for  to  reajon 
from  the  fads  with  which  they  are  fupplied  is  no  more  the 
province  of  the  perfon  who  discovers  them,  than  of  him  to 
whom  they  are  difcovered. 

One  of  the  moll:  Ample  of  all  phlogiftlc  proceflfes  is  that  in 

which  metals  are  ignited  in  dephlogiflicated  air.     I  therefore 

3  began 


1 

relating  to  Air  and  JVater,  28 1 

began  with  this,  with  a  view  to  afcertaiii  whether  any  'water 
is  produced  when  the  air  is  made  to  dii-ippear  in  it.  Accord- 
ingly, into  a  glafs  veflel  containing  7  ounce  meafures  of  pretty- 
pure  dephlogifticated  air,  I  introduced  a  quantity  of  iron  turn- 
ings (which  is  iron  in  Imall  tliin  pieces,  exceedingly  conve- 
nient for  thefe  and  many  other  experiments)  b.aving  previoun>- 
made  them,  together  with  the  veflel,  the  air,  and  the  mercury 
by  which  it  was  confined,  as  dry  as  I  poilibly  could.  Alfo,  to 
prevent  the  air  from  imbibing  any  moidure,  I  received  it  imme- 
diately in  the  veflel  in  which  the  experiment  was  made,  from 
the  procefs  of  procuring  it  from  red  precipitate;  fo  that  it  had 
never  been  in  contact  with  any  water.  ■       ~-  ',  t     - 

I  then  fired  the  iron,  by  means  of  a  burning  lens,  and  pre- 
fently  reduced  the  7  ounce  meafures  of  air  to  .65  ;   but  I  found  no 
more  water  after  this  procefs  than  I  imagined  it  had  not  been 
poflible  for  me  to  exclude,  as   it  bore  no  proportion  to  the  air 
which  had  difappeared.     Examining  the  refiduum  of  the  air,  I 
found  one-fifth  of  it  to  be  fixed  air,  and  when  I  tried  the  purity 
of  that  which  remained  bv  the  teff  of  nitrous  ain  it  did  not 
appear  that  aay  phlogifticated  air  had  been  produced  in  the  pro- 
cefs :   for  though  it  was  more  impure  than  I  luppofe  the  air 
with  which  I  began  the  experiment  muft  have  been,  it  was  not 
more   fo  than  the  phlogifticated  air  of  the  7  ounce   meafures, 
which  had  not  been  affeiled  by  the  procefs,  and  which  mufl: 
have  been  contained  in  the  refiduum,  would  neceflfarily  make 
it.     In   this  cafe  one  meafure  of  this  refiduum  and  two  of  ni- 
trous air  occupied  the  fpace  of  .32.-  ' 

In  another  experiment  of  this  kind,  ten  ounce  meafures  of 
dephlogiflicated  air  were  reduced  to  .8,  and  by  wafhing  in  lime 
water  to  .38.     In  another  experiment,  in  which  7I  ounce  mea- 
fures  of  dephlogiflicated  air  were   reduced  to   half  an  ounce 
Vol,  LXXV".  O  o  meafure, 


282  Dr.  pKif.sTr,EY*5  Experiments  and  Obfervations 

ineafure,.  of  which  one-fifth  was  fixed  air,  the  refiduum  was 
quire  as  pure  as  the  air  with  which  1  hegan  the  experiment,  ths 
tell  with  nitrous  air,  in  the  proportions  above-mentioned^ 
giving. 4  in  both  caies.  To  what  circumftance  the.  difference 
mip'ht  be  ovvino- 1  cannot  tell. 

In  thefe  experiments  the  fixed  .air  miifl:,  I  prefume,  have  been 
formed  by  the  union  of  the  phiogifton  from  the  iron  and  tho 
dephlogifticated  air  in  which  it  was  ignited;  but  the  quantitjj 
of  it  was  very  imall-in  proportion  to  the  air  which  had  difap- 
peared,  aiKl  at  that  time  Ihad  no  fufpicion  that  the  iron-,  which, 
had  been  melted,  and  gathered  into  round  balls,  could  hav*5 
imbibed  it ;  a  melting  heat  having  been  fufhcient,  as  I  had 
imagined,,  to  expel  every  thing  that  was  capable  of  affuming 
the  form  of  air  from  any  fubRance  whatever.-  I  was  therefore 
intirely  at  a  lofs  about  wl:^at  raufthave  become  of  the  air. 

Seniible,  however,  that-  fuch  a  quantity  of  air  mufl  have- 
been  ivrxSihtdhy  fomething  to  which.it  muft^have  given  a  very. 
perceivable  addition  of  weighty  and  feeing^  nothing  elfe  that 
could  have  Imbibed  it,:  it  occurred' to  me  to  weigh  the  calx  into 
which  the  iron  had  been  reduced;  and  I  prefently  found,  that 
the  dephlogiiliicated  air  had  adually  been  imbibed. by  the  melted 
iron,  in  the  fiirDe  manner  as  inflammable  air^  in.,  my  former 
experiments,  had  been. imbibed  by  the  melted  calces  of  metals, 
however  impofiible  fuch  an  abfbrpxion-  might  have  appeared  to 
xnt  a  priori.  In  the  firfl  infl:ance,„  about  twelve  ounce  mea- 
liires  of  d^phlogiilicated  air  had  difappeared,.  and  the  iron  had 
gained  -fix  grains  in  weight,  Repeating  the  experiment  very 
frequently,  I  always  found,  that  other  quantities  of  iro;i, 
treated  in  the  fame  ma.iiner,  gained  limilar  additions  of  weighty, 
which  \yas  always  very,  nearly  that  of  the  air  which  had  dif- 
a-ppeated*. 

This 


'^r elating  to  Air  and  Water,  283 

This  calx  of  irdn,  I  then  concluded,  was  by  no  means  what 
.1  had  before  taken  it  to  be,  'vlz,  o.  pure  calx  ox  flag  ^  but  either 
the  calx,  or  the  iron  itfelf,  fltturated  with  pure  air.  This  cal=- 
ciform  fubftance  I  found,  by  various  experimejits,  to  be  the- 
fame  thing  with  x\\Qfcales  that  fly  from  iron  when  it  h  made 
red-hot,  or  the  fubftanee  into  which  it  -runs  in  a  very  intenfe 
heat,  in  an  open  fire. 

Concludinp^  from  the  preceding  experiment,  that  iron,  fuffi- 
ciently  heated,  was  capable  of  faturating  itfelf  with   pure  air, 
extrai^ed  from  the  mafs  of  the  atmofphere,  I  then  proceeded  to 
melt  it  with  the  heat  of  a  burning  lens  in  the  open  air ;  and  I 
prefently  found,  that  perfect  iron  was  eafily  fufed  in  this  way, 
and  continued  in  this  fufion  a  certain  time,  exhibiting  the  ap- 
pearance of  bGiling  o\' throwing  out  air,  whereas  it  was  on  the 
contrary  imbibing  air;  and  when  it  was  lliturated  the  fufion 
ceafed,  and  the  heat  of  my  lens  could   not   make  any  farther 
impreflion  upon  it.     When  this   was  the  cafe,  I  always  found 
that  it  had  gained  weight  in  the  proportion  of  7!  to  24,  which 
is  very  nearly  one-third  of  its  original  weight.     The  fame  was 
the  etfe^l  when  J  melted j/?^^/ in  the  fame  circumflances,  and 
alfo  ^v^x-'j  kind  of  iron  on  which  the  experim.ent  could  be  tried. 
But  I  haveiome  reafon  to  think,  that  w^ith  agreater  degree  of 
heat  than  I  could  apply,  the  iron  might  have  been  kept  in  a 
flate  of  fufion  fomev/hat  longer,  and  by  that  means  have  im- 
bibed  more   air,    even   more   than   one-third   of   its   original 
weight. 

There  was  a  peculiar  circumftance  attending  the  melting  of 
cafi  iron  with  a  burning  lens,  which  made  it  impoffible  to  afcer* 
tain  the  addition  that  was  made  to  its  weight,  and  at  the  fame 
time  afforded  an  amazing  fpe^lacle  ;  for  the  moment  that  any 
quantity  of  it  Vv^as  melted,  and  gathered  into  a  round  ball,  it  begnn 

O  o  2  to 


.284  Dr,  Prie&tley's  Experiments  andObfer'vations 
.to  dilperfe  in  a  thoufand  diredions,  exhibiting  the  appearance  of 
.  a  mofl  beautiful  fire-work,  fome  of  the  particles  flying  to  the 
diftance  of  half  a  yard  from  the  place  of  fufion  ;  and  the  whole 
was  attended  with  a  confiderabie  hifling  noife.  Some  of  the 
largeO:  pieces  which  had  been' dlfperfed  in  this  manner  1  v/as 
able  to  collect,  and  having  fubjedled  tliem  to  the  heat  of  the 
lens,  they  exhibited  the  ilime  appearance  as  the  larger  mafs  from 
which  they  had  been  fcattered. 

When  I  melted  this  call:  iron  in  the  bottom  of  a  deep  giafs 
receiver,  in  order  to  colledl  all  the  particles  that  were  difperfed, 
they  firmly  adhered  to  the  glafs,  melting  it  fuperficially, 
though  without  making  it  crack,  fo  that  it  was  flill  impoffible 
to  coUeft  and  weigh  the  particles.  However,  I  generally 
found  that,  notwithilanding  the  copious  difperfion,  what  re- 
mained after  the  experiment  rather  exceeded  than  fell  fliort  of 
the  original  weight  of  the  iron.  Sometimes  a  piece  of  com- 
mon iron,  and  efpecially  fleel,  would  make  a  little  hifling  in 
the  fufion,  and  a  particle  or  two  would  fly  oif ;  but  this  was 
never  confiderabie  *. 

Having  now  procured  what  I  thought  to  be  a  new  calx  of 
iron,  or  a  calx  faturated  with  pure  air,  1  endeavoured  to  revive 
it  by  making  it  imbibe  inflammable  air,  in  the  lame  manner 
that  I  had  before  m.ade  iron,  and  various  other  metals,  by  melt^ 
ing  them  in  a  velTel  containing  inftammable  air.  In  this  I  fuc- 
ceeded ;  but  in  tlie  courfe  of  the  experiment  a  new  and  very 
unexpefted  appearance  occurred.  1  took  a  piece  of  iron  which 
I  had  faturated  with  pure  air,  and  putting  it  into  a  glafs  vefTel 

^   On   being  informed   of  the    above-mentioned    phfetiomcna,  Mr.  Watt  con- 
cluded, that  the  b:ifis  of  the  dephlogiilicated  air  united  to  the  phlogifton  of  the  iron, 

* 

and  formed  luater,  which  was  attracted  by,  and   remained  Tq  firmly  united  to  the 
,calx  of  iron,   as  to  rcfirt  the  efTcffts  of  heat  to  fcpnrate  them, 

containing 


relating  to  Air  iind  IVater,  2B5 

containing  inflammable  air,  confined  by  water,  threw  upon  it 
the  focus  of  the  lens,  and  prefently  perceived  the  inflammable 
air  to  difappear,  and  without  thinking  of  any  thing  efcaping 
from  the  calx  of  iron  (which  had  been  fubjeded  to  a  greater 
heat  before)  I  imagined  that  I  fhould  have  found  the  addition  of 
the  weight  of  air  in  the  iron,  and  the  refult  might  be  an  i.'on 
, different  from  the  common  fort.  But  I  found,  to  my  furprife, 
that  the  iron,  which  had  exhibited  no  new  appearance  in  thi^ 
mode  of  treatment,  had  loft  weight,  inftead  of  gaining  any. 
The  piece  of  iron  on  which  I  made  this  firft  experiment  weighed. 
Ill  grains,  and  71  ounce  meafures  of  inflammable  air  had  dif- 
appeared  while  the  iron  had  loft  2|  grains. 

Confidering  the  quantity  of  inflammable  air  that  had  difap- 
peared,  "ch.  7^  ounce  meafures,  and  the  dephlogifticated  air 
which  had  been  expelled  from  the  iron,  ^v's.  2!  grains,  which 
is  equal  to  about  4.1  ounce  meafures,  I  found  that  they  were 
very  nearly  in  the  proper  proportion  to  faturate  each  other, 
when  decompofed  by  the  eletflrical  fpark,  vh.  X^no  meafures  of 
inflammable  air  to  one  of  dephlogifticated  air.  I  therefore  had 
now  no  doubt  but  that  the  two  kinds  of  air.  had  united,  and 
had  formed  either jlv^ J  air  or  water  ;  but  which  it  was  I  could 
not  tell,  having  had  water  on  the  receiver  in  which  the  experi- 
ment was  made,  and  havino:  neo-lecled  to  examine  the  ftate  ot 
the  air  that  remained,  except  in  a  general  way,  by  which  I 
found,  that  it  was  ftill,  to  appearance,  as  inflammable  as  ever.  . 

With  a  view  to  determine  whether  j^'a.W  air,  or  water^  would 
be  the  produce  of  this  mode  of  combining  inflammable  and 
dephlogifticated  air,  I  repeated  the  experiment  in  a  veflel  in 
which  the  inflammable  air  was  confined  by  mercury,  and  both 
the  veflel  and  the  mercury  had  been  previoufly  made  as  dry  as 
poflible.     I  had  no  fooner  begun  to  heat  the  iron,  or  x^t\\evjlag, 

iU 


dtS  Dr.  Priestley's  Experiments  and  ObfervaUons 
ill  thcTc  circumftances,  than  I  perceived  the  air  to  diminifh,  and 
at  the  lame  time  the  iiiiide  of  the  veffel  to  grow  very  cloudy, 
with  particles  of  dew,  that  covered  almoft  the  whole  of  it. 
Thefe  particles  by  degrees  gathered  into  drops,  and  ran  down  the 
IkIcs  oi:  the  veflel  in  all  places,  except  where  it  was  heated  by 
tli'^  fu n- beams  ;  fo  that  it  then  appeared  to  me  very  evident, 
that  -water ^  with  or  without  fixed  air,  was  the  produce  of  the 
inflammable  air,  and  t!ie  pure  air  let  loofe  from  the  iron  in  this 
ijvGxle  -of  operation,.;  though  afterwards  I  was  taught  by  Mr. 
Watt  to  correct  this  hypothefis,  and  to  account  for  this  refult 
i^i  a  different  manner.  When  I  had  examined  the  remaining 
air,  it  was  as  inflammable  as  ever,  without  containing  any 
mixture. of  fixed  air  at  all. 

When  I  colleded  the  water  which  wms  produced  in  this  ex- 
periment  by  means  of  a  piece  of  filtering  paper,  carefully  in- 
troduced to  abforb  it,  I  found  it  to  be,  as  nearly  as  poflible,  of 
the  fame  weight  with  that  which  had  been  loll:  by  the  iron  : 
and  alio,  in  every  experiment  of  this  kind,  in  which  1  attended 
to  this  circumflance,  I  found  that  the  quantity  of  inflammable 
air  which  had  difappeared  was  about  double  to  that  of  the  de- 
phlogifticated  air  fet  loofe  from  the  iron,  fuppohng..that  weight 
to  have  been  reduced  into  air.  Thus  at  one  .time!  made  a  piece 
of  this  flagambibe  ,5!  ounce  meafures  of  inflammable  air,  while 
it  lofl  as  much  as^the  weight  of  about  3  ounce  meafure-s  of  de- 
phlogifticated  air,  and  the  water  colledted  weighed  2  grains. 
Another  time  a  piece  of  flag  lofl:  1.5  grains,  .and  the  water 
produced  was  1.7  grains;  but  per  fed  accuracy  is  not  to  be  ex- 
pected. ,1  fliall  only  mention  one  more  experiment  of  this 
kind,  in  which  t\  ounce  mealures  .of  inflammable  air  were 
reduced  to  .92  ounce  meafiire,  and  the  iron  had  lofl:  2  grains,, 
xqual  in  weight  to  3.3   ounce  meafures  of  dephlogiilicated  air. 

In 


relating  to  Air  and  Water,  2  S  7 

In  all  the  above-mentioned  experiments,  the   Inriammable  air 
was  that  which  is  produced. by  the  folution  of  iron  in  acids. 

As   before- I   had   finiilied   this  courfe  of  exper.ments  I  had- 
iatistied  myfelf  that  inflammable  air  ahvvays  contains  a  portit)ii 
of  water,  and   alfo,  that  when  it  has  been  fome  time  confinccV 
by  water,  it  imhibes  more,   fo  as  to  be  increafed  in  its    fpecifiO 
gravity  by  that  means,  I  repeated  the  experiment  with  inflam- 
mable air  which  had  not  bee:i  coniined  by  water,  but  which  was-. 
received  in  a  veiiel  of>  dry  mercury  from  the-,  veflelin  which  it 
was  generated;,  but   I   prefentiy  perceived  that- vrater  was  pro-- 
duccd  in  this- cafe  alio,  and  .to  appearance  as  copioufly  as  in  the- 
former  experiment.     Indeed,  the   quantity  of  water  produced, 
which  fo  greatly,  exceeded   the  weiglit  of  all  the  inflammable 
air,  is  fufficient  to  prove  that   it  muft  have  had  fome  othen^ 
fource  than  any  conftituent  part  of; that  air^  o-r  the  whole  of  ity 
together  with   the  water  contained  in-  it;  without  taking  into-- 
coniideration  the  correfponding  lofs  of  weight  in  the  iron. 

I  m.ufl:  here  obferve,  that  the  iron,  flag-  which  1  had  treated  in^' 
tills  manner,  and   which  had   thereby  loft  the  weight  which  ^ 
it  had  acquired  by  melting  in  dephlogifticated   air,  became  ^^r- • 
fe5l  iron  as   at   firft,  and  was  then  capable  of  being  melted  by 
the  burning  lens  again  ;  fo  that  the  fame  piece,  of  iron  wouldi' 
ferve  for  thefe  experiments  as  long  as  the  operator  ihouldchufe. 
It  was  evident,  therefore, .that  if  the   iron   had  lofl:  its  phlo- 
gifton  in  the  preceding  fuflon,  it  had  acquired  it  again  from  the- 
inflammable  air  which  it  had  abforbed  ;  and  I  do  not  fee  how  the  • 
experiment  can  be  accounted  for  in  any  other  way,  w^iich  ne— 
ceflarily  implies  the  reality  of  phloglfton  as  a  conftituent  prin- 
ciple in  bodies.     This,  at  leafl,  is  the  mofl  natural  way  ofA 
a,ccounting  for  the  appearanceSc 

5.  Having^; 


28 S        Dr,  Priestley's  Experiments  and  Obfeyvations 

Having  had  this  fuccefs  with  the  calx,  or  Icales  of  iroji,  I 
tried  the  calx  of  copper,  or  thofe  fcales  which  fly  from  it  whea 
it  is  made  red-hot ;  and  I  found  water  produced  in  the  inflam- 
mable air  in  the  fame  manner  as  when  I  ufed  the  fcales  of  iron 
in  the  fiime  circumftances.  I  alfo  had  the  fame  refult  when  I 
Y  (tyw^^^  precipitate  per  fe  in  inflammable  air;  but  having  at  that 
time  a  very  weak  winter's  fun,  I  could  not  make  the  experi- 
ment with  fo  much  advantage  as  I  could  have  Vv'iflied. 

Iron,  I  found,  acquired  this  additional  weight  by  melting 
in  an  earthen  retort,  as  well  as  in  the  open  air  by  the  fun- 
beams,  if  it  were  poffible  for  it  to  attra61;  air,  or  whatever  elfe 
it  is  that  is  the  immediate  caufe  of  its  additional  w^eight. 
Three  ounces  of  common  iron  filings,  expofed  to  a  ftrong  heat 
in  an  earthen  retort,  gained  1 1  dwts,  or  264  grains,  and  yet 
was  very  far  from  having  been  completely  fufed.  Having  a 
glafs  tube  communicating  with  the  retort,  in  order  to  collect 
any  air  that  the  iron  filings  might  give  out,  I  found  that  when 
they  were  very  hot,  the  water  afcended  within  the  tube  ;  which 
fliews  that  the  iron  was  then  in  a  ftate  of  abforblng,  and  not 
of  giving  out  any  air. 

Seeing  fo  much  water  produced  in  thefe  experiments  with 
inflammable  air,  I  was  particularly  led  to  reflcft  on  the  relation 
which  they  bore  to  each  other,  and  efpecially  to  Mr.  Cav^.n- 
dish's  ideas  on  the  fubjeil.  He  had  told  me  that,  notwith- 
ftanding  the  experiments  of  which  I  had  given  an  account  to 
the  Royal  Society,  and  from  which  I  had  concluded  that  in- 
flammable air  v/as  pure  phlogifton,  he  was  perfuaded  that  ^uDater 
w^as  effential  to  the  produdlion  of  it,  and  even  entered  into  it 
as  a  conftituent  principle.  At  that  time  I  did  not  perceive  the 
force  of  the  arguments  which  he  flated  to  me,  efpecially  as,  in 
the  experiments  with  charcoal,  I  totally  difperfed  any  quantity 

of 


relating  io  ^/V  and  Water,  289 

of  it  with  a  burning  lens  tn  vacuo,  and  thereby  filled  my 
receiver  with  nothing  but  inflammable  air.  I  had  no  fufpicioli 
that  tbe  w^et  leather  on  which  my  receiver  ftood  could  have 
any  influence  in  the  cafe,  while  the  piece  of  charcoal  was  fub- 
je6t  to  the  intcnfe  heat  of  the  lens,  and  placed  feveral  inches 
above  the  leatlier.  I  had  alfo  procured  inflammable  air  from 
charcoal  in  a  glazed  earthen  retort  two  whole  days  fucceffively, 
in  which  it  had  given  inflammable  air  without  Intermlflion. 
Alfo  iron  filings  in  a  gun-barrel,  and  a  gun-barrel  itfelf,  had 
always  given  inflammable  air  whenever  I  tried  the  experiment. 

Thefe  circumflances,  however,  deceived  me,  and  perhaps 
would  have  deceived  any  other  perfon  ;  for  I  did  not  know, 
and  could  not  have  believed,  the  powerful  attradion  that  char- 
coal, or  iron,  appear  to  have  for  water  when  they  are  intenfely 
hot.  They  will  find,  and  attra£l  it,  in  the  mldfl:  of  the  liotteft 
fire,  and  through  any  pores  that  may  be  left  open  in  a  retort ; 
and  iron  filings  are  feldom  fo  dry  as  not  to  have  moifture 
enough  adhering  to  them,  capable  of  enabling  them  to  give  a 
confiderable  quantity  of  inflammable  air.  But  my  attention 
being  now  fully  awake  to  the  fubje6t,  I  prefently  found  that 
the  circumftances  above-mentioned  had  adually  mifled  me;  I 
mean  with  refpeil  to  the  conclujion  which  T  drew  from  the  expe- 
riments, and  not  with  refpe^t  to  the  experiments  themfelves, 
every  one  of  which,  I  doubt  not,  will  be  found  to  anfwer, 
whenever  they  are  tried  by  perfons  of  fufficient  Ikill  and  pro- 
perly attentive  to  all  the  circumflances. 

Being  thus  apprifed  of  the  influence  of  unperceived  moiflure 
in  the  production  of  inflammable  air,  and  willing  toafcertain  it 
ta my  perfeift  fatisfaClion,  I  began  with  filling  a  gun-barrel  with 
iron  filings  in  their  common  ftate,  without  taking  any  parti- 
cular precaution  to  dry  them,  and  I  found  that  they  gave,  air  as 

Vol.  LXXV.  P  p  they 


2<^or  T>^»  Priestley's  Experiments  and  Obfervations 
they  had  been  ufed  to  do,  and  continued  to  do  fo  many  hours;; 
1  even  got  ten  ounce  meafures  of  inflammable  air  from,  two 
ounces  of  iron  filings  in  a  coatedglafs  retort.  At  length,  how- 
ever, the  produclion  of  inflammable  air  from  the  gun-barrel- 
ceafed  ;  but  on  putting  water  into  it,  the  air  was-  produced' 
again,  and  a  few  repetitions  of  the  experiment  fully  fatisfied 
me  that  I  had  been  too  precipitate  in  concluding  that  inflam- 
mable air  is  pure  phlogifksn, 

I  then  repeated  the  experiment  with  the  charcoal,  making 
the  receiver,  the  ftand  on  which  r  placed  the  charcoal,  and  the- 
charcoal  itfelf,  as  dry  and  as  hot  as  poffible,  and  ufing  cement 
inftead  of  a  wet  leather  to  exclude  the  air.  In  thefe  circum- 
ilances  I  was  not  able,  with  the  advantage  of  a  good  fun,  and- 
an  excellent  burning  lens,  to  decompofe  quite  fo  much  as  two 
grains  of  the  piece  of  charcoal,  which  gave  me  ten  ounce  mea- 
fures of  inflammable  air;  and  this,  I  imagine,  was  eiFe<£led  by 
means  of  fo  much  moifture  as  was  depofited  from  the  air  in  its 
flate  of  rarefa<Sl:ion,  and  before  it  could  be  drawn  from  the 
jeceiver.  To  the  produ<5lion  of  this  kind  of  inflammable  air  I 
vv^as  therefore  now  convinced,  that- water  is  as  necefl'ary  as  to 
that  from  iron. 

It  was  rn  this  flate  of  my  experiments  that  I' received  an  au- 
thentic account  of  thofe  of  M.  Lavoisier,  on  tranfmitting  water 
through  an  hot  iron  tube  and  alfo  throug'h  a  hot  copper  tube 
containing  charcoal,  and  thereby  procuring  large  quantities  of ' 
inflammable  air,  M.  Lavoisier  hlmfelf  having  been  fo  obliging 
as  to  fend  me  a  copy  of  his  Memoir  on  that  fubjedl.  1  had 
heard  an  account  of  the  experiments  fome  months  before;  but 
it  was  fo  imperfeft  a  one,  that  I  own  I  paid  little  attention  to 
them.  At  this  time,  however,  I  was  prepared  to  be  fuiBciently 
f«nfible  of  their  value. 

In 


relalhig  to  Air  dnd  Water.  -sjpi 

In  my  lafl:  communications  to  the  Royal  Society,  it  will  be 
>reen  that  I  had  tranfmitted  the  vapour  of  feveral  fluid  fub- 
jflances  through  red-hot  earthen  tubes,  and  thereby  prcvured 
different  kinds  of  air.  M.  Lavoisier  adopted  the  fame  pro- 
cefs,  but  ufed  an  iron  tube ;  and  by  means  of  that  circumftance 
-made  a  very  valuable  difcovery  which  had  efcaped  me.  I  had 
indeed  on  one  occalion  made  ufe  of  an  iron  tube,  and  tranfm^it- 
ted  fleam  through  it ;  but  not  having  at  that  time  any  view  to 
the  produtflion  of  alr^  I  did  not  colleft  it  at  all,  contenting 
■myfelf  with  obferving  that  water-,  after  being  made  red-hot 
was  ftill  water,  there  being  no  change  in  its  fenfible  properties. 
Being  now  farther  infi:ru(9:ed  by  the  experiment  of  M.  La- 
voisier, I  was  determined  to  repeat  the  procefs  witii  all  the 
attention  I  could  give  to  it ;  but  I  fliould  not  have  done  this 
with  fo  much  advantage,  if  I  had  not  had  the  affiftance  of  Mr» 
Watt,  who  alway-s  thought  that  M.  Lavoisier's  experi- 
ments by  no  means  favoured  the  conclufion  that  he  drew  from 
them.  As  to  myfelf,  I  was  a  long  time  of  opinion  that  his 
■conclufion  was  juft,  and  that  the  inflammable  air  was  really 
furnifhed  by  the  water  being  decompofed  in  the  procefs.  But 
though  I  continued  to  be  of  this  opinion  for  fome  time,  the 
frequent  repetition  of  the  experiments,  with  the  light  which 
Mr.  Watt's  obfervations  threw  upon  them,  fatisfied  me  at 
length  that  the  inflammable  air  came  principally  from  the  char- 
coal, or  the  iron. 

I  fhall  firfl  relate  the  refult  of  the  experiment  that  was  made 
with  charcoal,  and  then  thofe  with  iron  and  other  fubftances,  in 
conta£l  with  which  (when  they  were  in  a  flate  of  fuiion,  or  at 
leaft  red-hot)  I  made  fleam,  or  the  vapour  of  other  liquid  fub- 
ilances,  to  pafs.  I  fhall  only  obferve  that,  previous  to  this,  I 
began  to  make  the  experiments  with  coated  glafs  tubes,  which 

P  p  2  I  found 


29 2  -^^^  Pbikstley*s  Experiments  and  Obfervat Ions 
I  found  to  anfwer  very  well  during  the  procefs,  though  they 
never  failed  to  break  in  cooling.  At  length  I  procured  a  tube 
of  copper^  on  which,  as  M.  Lavoisier  difcovered,  fteam  had 
no  efFe6l ;  and  at  laft  I  made  ufe  of  earthen  tubes,  with  which 
Mr.  Wedgewoou,  that  mod  generous  promoter  of  fcience, 
liberally  fuppHed  me  for  the  purpofe  ;  and  thefe  glazed  on  the 
outfideonly  I  find  far  preferable  to  copper.  They  are,  indeed, 
every  thing  that  I  could  wifli  for  in  experiments  of  this  khid ; 
the  reafon  of  which  u'ill  appear  in  my  account  of  another  courfe 
of  experiments,  which  I  hope  to  lay  before  the  Society  in  due, 
time. 

Tlie  difpofition  of  the  apparatus,  with  which  thefe  experi- 
ments were  made,  was  as  follows.  The  water  was  made  to  boil 
in  a  glafs  retort,  which  communicated  with  the  copper  or 
earthen  tube  which  contained  the  charcoal  or  iron,  &c.  and 
which,  being  placed  in  an  horizontal  pofition,  was  furrounded 
with  hot  coals.  The  end  of  this  tuhe  oppofite  to  the  retort 
communicated  with  the  pipe  of  a  common  worm  tub,  fuch  as 
is  generally  ufed  in  diftillations,  by  means  of  which  all  the 
fuperfluous  fleam  was  condenfed,  and  collected  in  a  proper  re- 
ceptacle, while  the  air  which  had  been  produced,  and  had 
come  along  with  it  through  the  worm  tub,  was  tranfmitted 
into  a  trough  of  water,  where  proper  veflels  were  placed  to 
receive  it,  and  afcertain  the  quantity  of  it;  after  which  I 
could  examine  the  quality  of  it  at  leifure. 

In  the  experiment  with  charcoal,  I  found  unexpected  diffi- 
culties, and  confiderable  variations  in  the  refult ;  the  proportion 
between  the  charcoal  and  water  expended,  and  alfo  between  each 
ofthemand  the  j/V  produced,  not  being  fo  nearly  the  fame 
as  I  imagined  they  would  have  been.  Alfo  the  quantity  of 
fixed  air  that  was  mixed  with  the  inflammable  air  varied  very 
4  much. 


relating  to  Air  and  Water.  293 

much.  This  laft  circumftance,  however,  fome  of  my  experi- 
ments may  ferve  to  explain.  Whenever  I  had  no  more  water 
than  was  fufficient  for  the  produdlon  of  the  air,  there  was 
never  any  fcnfible  quantity  of  uncombined  fixed  air  mixed  with 
the  inflammable  air  from  charcoal.  This  was  particularly  the 
cafe  when  I  produced  the  air  by  means  of  a  burning  lens  in  an 
exhaufled  receiver,  and  alfo  in  an  earthen  retort  with  the  appli- 
cation of  an  intenfe  heat.  I  therefore  prefume,  that  when  the 
ileam  tranfmitted  through  the  hot  tube  containing  the  charcoal 
was  very  copious,  the  fixed  air  in  the  produce  was  greater  than 
it  would  otherwife  have  been.  The  extremes  that  I  have  ob* 
ferved  in  the  proportion  of  the  fixed  to  the  inflammable  air  have 
been  from  one-twelfth  to  one-fifth  of  the  whole.  As  I  gene- 
rally produced  this  air,  the  latter  was  the  ufual  proportion  ;  and 
this  was  exclufive  of  the  fixed  air  that  was  intimately  combined 
with  the  inflammable  air,  and  which  could  not  be  feparated 
from  it  except  by  decompofition  w^ith  dephlogifticated  air ;  and 
this  combined  fixed  air  I  fometimes  found  to  be  one-third  of  the 
whole  mafs,  though  at  other  times  not  quite  fo  much. 

To  afcertaln  this,  1  mixed  one  meafure  of  this  inflammable 
air  from  charcoal  (after  the  uncombined  fixed  air  had  been  fepa- 
rated from  it  by  lime-water)  with  one  meafure  of  dephlogifti- 
cated air,  and  then  fired  them  by  the  ele£lric  fpark.  After  this 
I  always  found  that  the  air  which  remained  made  lime-water 
very  turbid,  and  the  proportion  in  which  it  was  now  dimi- 
nifhed,  by  wafliing  in  lime-water,  fhewed  the  quantity  of 
fixed  air  that  had  been  combined  with  the  inflammable.  That 
the  fixed  air  is  not  generated  in  this  procefs,  is  evident  from 
there  being  no  fixed  air  found  after  the  explofion  of  dephlogifti- 
cated air  and  inflammable  air  from  iron. 

Not  with' 


294         ^^'  PiiiESTLEY^s  Experiments  and  Ohfervations 

Notwith Handing  the  above-mentioned  variations,  the  lofs  of 
weight  in  the  charcoal  was  always  much  exceeded  by  the  weight 
of  the  water  expended,  which  was  generally  more  than  double 
of  the  charcoal ;  and  this  water  was  intimately  com.bined  with 
the  air ;  for  when  I  received  a  portion  of  it  in  mercury,  no 
water  was  ever  depofited  from  it. 

The  experiment  which,  upon  the  whole,  gave  me  the  moft 
fatisfaclion,  and  the  particulars  of  which  I  fhall  therefore  re- 
cite, was  the  following.  Expending  94  grains  of  perfe(5l 
charcoal  (by  which  I  mean  charcoal  made  with  a  very  ftrong 
lieat,  fo  as  to  expel  all  fixed  air  from  it)  and  240  grains  of 
water,  I  procured  840  ounce  meafures  of  air,  one-fifth  of 
which  was  fixed  air,  and  of  the  inflammable  part  nearly  one- 
third  more  appeared  to  be  fixed  air  by  decompofition. 

Receiving  this  kind  of  air  in  a  variety  of  experiments,  but 
not  in  the  preceding  ones  in  particular  (for  then  I  could  not 
have  afcertained  the  quantity  of  it)  confiding  of  fixed  and  in- 
flammable air  together,  I  found  fome  variations  in  its  fpecific 
gravity,  owing,  I  imagine,  to  the  ditterent  proportions  of 
iixed  air  contained  in  it ;  but  upon  the  whole,  I  think,  that  the 
proportion  of  14  grains  to  40  ounce  meafures  is  pretty  near  the 
truth,  when  the  proportion  of  fixed  air  is  about  one-fifth  of  the 
whole.  With  refpe£l  to  the  weight  of  the  inflammable  air  after 
the  fixed  air  was  feparated  from  it,  I  found  no  great  difi^erence, 
and  think  it  may  be  eftimated  at  8  grains  to  30  ounce  meafures. 

Upon  thefe  principles,  the  whole  weight  of  the  840  ounce 
meafures  of  air  will  be         -     294  grains 

that  of  the  charcoal  will  be      94 
that  of  the  water  -         240 


334  which,  confidering  the  na- 

7  ture 


relating  to  Air  and  Water,  295 

ture  of  the  experimenr,  will  perhaps  be  thought  to  be  tolerably 
ikear  that  of  the  air. 

If  the  air  be  analyzed,  the  840  ounce  meafures  will  be 
found  to  contain    -    168  of  uncombined  fixed  air  =  151  grains. 

and   672  impure  imflanamable       =179 

fo  that  the  wdiole     840  will  weigh  -         -       330 

Lailily,  if  the  672  ounce  meafures  of  impure  inflammable 
air  be  decompofed,  it  will  be  found  to  contain 

164  ounce  meafures  of  fixed  air=  147.6  grs,. 
and  508  inflammable         -         -       =    30.7 

fo  that  the  whole  672  will  weigh         -  -  ^1^'3 

which  is  very  near  to  179,  the  weight  of  the  whole  together. 

It  may,  however,  be  lafely  concluded  from  this  experiment, 
and  indeed  from-  every  other  that  I  made  with  charcoal,  that 
there  was  no  more  pure  inflammable  air  produced  than  the 
charcoal  itfelf  may  be  very  well  fappofed  to  have  iupplied. 

There  is,  therefore,  no  reafon  for  deferting  the  old  eftablilhed* 
hypothefis  of /'y^/^^^i?^  on  account  of  thefe  experiments,  fince 
the  fa6l  is  by  no  means  inconfiflent  with  it.  The  pure  inflam- 
mable air  with  the  water  neceflarily  contained  in  it  would 
weigh  no  more  than  about  30  grains,  while  the  lofs  of  weight 
in  the  charcoal  was  94  grains.  But  to  this  muft  be  added  the 
phlogifton  contained  in^  392  ounce  meafureS'  of  fixed  air,, 
which,  according  to  Mr.  Ki swan's  proportion,  will  be  nearly 
6^  grains,  and  this  and  the  30  grains  will  be  95  grains. 

The  bafis  to  this  fixed  air,  as  well  as  to  the  inflamxmable, 
miifl:  have  been  furnifhed  by  t\iQ  water  y  and  from  this  it  may 
be  concluded,  that  the  w^ater  muft  have  been  fo  far  altered  as 
to-be  changed  into  fixed  air,  which  will  be  thought  not  to  be 
any  great  paradox,  if  it  be  confidered.  that,  according  to  the 

latefli 


296  T^r.  Priestley's  Experiments  and  Ohfervat ions 
lateft  difcoveries,  fixed  air  and  water  appear  to  confiil:  of  the 
fame  ingredients,  namely  dcphiogifLicatcd  and  inflammable  air. 
However,  in  this  change  of  the  water  we  cannot  be  abfokitely 
fure  that  the  fame  proportion  of  the  ingredients  is  contained,  and 
therefore  it  cannot  be  abfolutely  determined  whether  the  inflam- 
mable air  which  it  contains  enters  wholly  into  the  fixed  air,  or 
not.  Farther  experiments,  or  a  careful  comparifon  of  thefe  ex- 
periments with  thofe  made  by  Mr.  Kir  wan  and  others,  may 
perhaps  throw  fome  light  tipon  this  fubjecl.  Whether  the  com- 
bined fixed  air  comes  wholly  from  the  charcoal,  or  whether  the 
charcoal  only  fupplies  the  phlogifton,  and  the  water  its  bafis, 
that  is,  the  dephlogifticated  air,  deferves  to  be  inveftigated. 

Before  I  conclude  my  account  of  the  experiments  with  char- 
coal, I  would  obferve,  that  there  is  another  in  which  I  place 
fome  dependance,  in  which,  with  the  lofs  of  178  grains  of 
charcoal,  and  528  grains  of  water,  I  procured  1410  ounce 
meafures  of  air,  of  which  the  laft  portion  (for  I  did  not  exa- 
mine the  reft)  contained  one-fixth  part  of  uncombined  fixed 
air.     This  was  made  in  an  earthen  tube  glazed  on  the  outfide. 

The  experiments  with  iron  were  more  fatisfa^lory  than  thof<2 
with  charcoal,  being  fubjedt  to  lefs  variation ;  and  it  is  ftill 
more  evident  from  them,  that  the  inflammable  air  does  not 
come  from  the  water,  but  only  from  the  iron,  as  the  quantity 
of  water  expended,  added  to  the  weight  of  the  air  produced, 
was  as  nearly  as  could  be  expe6led  in  experiments  of  this  kind,  . 
found  in  the  addition  of  weight  gained  by  the  iron.  And 
though  the  inflammable  air  procured  in  this  procefs  is  between 
one-third  and  one-half  more  than  can  be  procured  from  iron  by 
a  folution  in  acids,  the  reafon  may  be,  that  much  phlogifton 
is  retained  In  the  folutions,  and  therefore  much  more  may  be 
expelled  from  iron,  when  pure  water,  without  any  acid,  takes 
the  place  of  it.     I  would  further  obferve,  that  the  produce  of 

air. 


relating  to  Air  andJValer,  297 

ail',  and  alfo  the  addition  of  weight  gained  by  the  iron,  are 
much  more  eailly  afcertained  in  thefe  experiments  than  the 
quantity  of  water  expended  in  them,  on  account  of  the  great 
length  of  the  vefTels  ufed  in  the  procefs,  and  the  different  quan- 
tities that  may  perhaps  be  retained  in  the  worm  of  the  tub, 
though  I  did  not  fail  to  ufe  all  the  precautions  that  I  could  think 
of  to  guard  againft  any  variation  on  thefe  accounts. 

Of  the  many  experiments  which  I  made  with  iron^  I  Ihall 
content  myfelf  with  reciting  the  following  refults.  With  the 
addition  of  267  grains  to  a  quantity  of  iron,  and  the  lofs  of 
336  grains  of  water,  I  procured  840  ounce  meafures  of  in- 
flammable air  ;  and  with  the  addition  of  140  grains  to  another 
quantity  of  iron,  and  the  confumption  of  253  grains  of  water, 
I  got  420  ounce  meafures  of  air*. 

The  inflammable  air  produced  in  this  manner  is  of  the 
llghtefl:  kind,  and  free  from  that  very  offmfive  fmell  which  is 
generally  occafioned  by  the  rapid  folution  of  metals  in  oil  of 
vitriol,  and  it  is  extricated  in  as  little  time  in  this  way  as  it  is 
poffible  to  do  it  by  any  mode  of  folution.  On  this  account  it 
occurred  to  me,  that  it  muft  be  by  much  the  cheapeft  method 
that  has  yet  been  ufed  of  filling  balloons  with  the  lightefl:  inflam- 
mable air.  For  this  purpofe  it  will  be  proper  to  make  ufe  of 
caft-iron  cylinders  of  a  confiderable  length,  and  about  three  or 
four  inches,  or  perhaps  more,  in  diameter.  Though  the  iron 
tube  itfelf  will  contribute  to  the  production  of  air,  and  there- 
fore may  become  unfit  for  the  purpofe  in  time ;  yet,  for  any 

*  If  the  perfeft  accuracy  of  the  former  of  thefe  experiments  may  be  depended 
on  (and  it  may  always  be  prefumed,  that  thofe  in  which  litth  water  is  expended 
are  preferable  to  thofe  in  which  more  is  confumed)  the  vjater  that  neceffarily  enters 
into  this  kind  of  inflammable  air  is  about  equal  in  weight  to  i\\q  phlogiJlon\.\\^X  is 
in  it.     But  I  propofe  to  give  more  particxilar  attention  to  this  fubjedl;. 

Vol.  LXXV.  Q^q  thing 


2^S         Dr.  Priest LLi''s  Experiments  and  ObJervatJons 

thing  that  I  know  to  the   contrary,  the  fame  tube  may   ferve 
for  a  very  great  number  of  proceffes,  and  perhaps  the  change . 
made  in  the  inlide  furface  may  protect  it  from  any  farther  adiori' 
of  the  water,   if  the  tube  be  of  fufficient  thicknefs  ;   but  this- 
can  only  be  determined  by  experiment. 

Some  eftimate  of  what  may  be  expeded  from  this  method  of 
procuring  inflammable  air  may  be  formed  from  the  following 
obfervations.  About  twelve  inches  in  length  of  a  copper  tube, 
three-fourths  of  an  inch  in-  diameter,  filled  with  iron  tuniings^ 
(which  are  more  convenient  for  this  purpofe  than  iron  flings^  as 
they  do  not  lie  fo.  clofe,.  but  admit  the  fteam  to  pafs  through 
their  interftices-)  when  it  was  heated,  and  a  fufficient  quantity  of 
fleam  pafled  through  it,  yielded  thirty  ounce  meafures  of  air  in 
fifty  feconds ;  and  eighteen  inches  of  another  copper  tube,  an 
inch  and  a  quarter  in  diameter,  filled  and  treated  in  the  fame 
manner,  gave  two  hundred  ounce  mealures  in  one  minute  and 
twenty-five  feconds ;.  {q>  that  this  lai^ger  tube  gave  air  in  pro- 
portion to  its  folid  contents  compared  with  the  Imaller ;  but  to 
what  extent  this  might  be  depended  upon  I  cannot  tell.  How- 
ever, as  the  heat  penetrates  fo  readily  to  fome  dlftance,  the  rate 
of  giving  air  will  always  be  in  a  greater  proportion  than  that  of 
the  limple  diameter  of  the  tube. 

The  following  experiment  was  maxie  with  a  view  to  afcertain 
the  quantity  of  inflammable  air  that  may  be  procured  in  this 
way  from  any  given  quantity  of  iron.  Two  ounces  of  iron^ 
or  960  grains,  when  diflblved  in  acids,,  will  yield  about  80a 
ounce  meafures  of  air ;  but  treated  in  this  manner  it  yielded 
1054  ounce  meafures,  and  then  the  iron  had  gained  329  grains 
in  weight,  which  is  little  fhort  of  one-third  of  the  weight  of 
the  iron. 

Confiderlnj^ 


rciaiing  to  u'fir  and  JVc2ter.  299 

Cv)!vrideimg  how  little  this  inflammable  ah*  weighs,  viz,  the 
V  hole  1054  ounce  meafures  not  more  than  63  grains,  and  the 
difficulty  of  afcertaining  the  lofs  of  water  to  fo  fmall  a  quan- 
tity as  this,  it  is  not  poffible  to  determine,  from  a  procefs  of 
this  kind,  how  much  water  enters  into  the  compofition  of  the 
inflammable  air  of  metals.  It  would  be  more  eafy  to  deter- 
mine this  circumllance  with  refpe«£l  to  the  inflammable  air  of 
charcoal,  efpecially  by  means  of  the  experiment  made  with  a 
burning  lens  ///  vacuo.  In  this  method  two  grains  of  charcoal 
gave  at  a  medium  thirteen  ounce  meafures  of  inflammable  air, 
which,  in  the  proportion  of  30  ounce  meaiures  to  8  grains, 
will  weigh  3.3  grains;  fo  that  water  in  the  compofition  of  this 
kind  of  inflammable  air  is  in  the  proportion  of  r  .3  to  2,  though 
there  will  be  fome  difficulty  with  refpe(5t  to  the  fixed  air  inti- 
mately combined  with  this  kind  of  inflammable  air. 

Since  iron  gains  the  lame  addition  of  weight  by  m.elting  in 
(JUphlogiJlicated  air,  and  alfo  by  the  addition  of  water  when 
red-hot,  and  becomes,  as  I  have  already  obferved,  in  all  re- 
fpe^lsthe  fame  fubftance,  it  is  evident,  that  this  air  or  water,  as 
exifting  in  the  iron,  is  the  very  fame  thing  ;  and  this  can 
hardly  be  explained  but  upon  the  fuppofition  that  water  confifts 
of  two  kinds  of  air ;  viz,  inflammable  and  dephlogifticated. 
I  fliall  endeavour  to  explain  thefe  procefles  in  the  following 
manner. 

When  iron  is  melted  in  dephlogifticated  air,  we  may  fuppofe 
that,  though  part  of  its  phlogifton  efcapes,  to  enter  into  the 
compofition  of  the  Imall  quantity  of  fixed  air  which  is  then 
procured,  yet  enough  remains  to  form  water  with  the  addition 
of  dephlogiificated  air  which  it  has  imbibed,  (o  that  this  calx 
of  iron  conlifts  of  the  intimate  union  of  the  pure  earth  of  irofi 
and  of  water  ;  and  therefore  when  the  fame  calx,  thus   fatu- 

0  q  3  rated 


^00         Dr.  Priestley's  Expenments  and  Obfcr-vations 

rated  with  water,  is  expofed  to  heat  In  inflammable  air,  this 
air  enters  into  it,  deftroys  the  attradion  between  the  water  and 
the  earth,  and  revives  the  iron,  while  the  water  is  expelled  in 
its  proper  form. 

Confequently,  in  the  procefs  with y?f^/«,  nothing  is  neceflary 
to  be  fuppofed  but  the  entrance  of  the  water,  and  the  expul- 
lion  of  the  phlogifton  belonging  to  the  iron,  no  more  phlo- 
gifton  remaining  in  it  than  what  the  water  brought  along  with 
it,  and  which  is  retained  as  a  conflituent  part  of  the  water, 
or  of  the  new  compound. 

Having  procured  water  from  the  fcales  of  iron  (which  I  mufl 
again  obferve  is,  in  all  refpe<3:s,  the  fame  fubflance  with  iron 
melted  in  dephlogiftlcated  air,  or  faturated  with  fteam  by  means 
of  heat)  and  havii^g  thereby  converted  it  into  perfecl  iron  again, 
I  did  not  entertain  a  doubt  but  that  I  fyiould  be  able  to  produce 
the  fame  effecl  by  heating  it  with  charcoal  in  a  retort;  and  I 
had  likewife  no  doubt  but  I  fhould  be  able  to  extraft  the  addi- 
tional weight  which  the  iron  had  gained  (viz.  one-third  of  the 
whole)  in  water.  In  the  former  of  thefe  conje6lures  I  was 
right ;  but  with  refpe6t  to  the  latter,  I  was  totally  miftaken. 

Having  made  the  fcales  of  iron,  and  alfo  the  powder  of 
charcoal  very  hot,  previous  to  the  experiment,  fo  that  I  was 
fatisfied  that  no  air  could  be  extracted  from  either  of  them  fe- 
parately  by  any  degree  of  heat,  and  having  mixed  them  toge- 
ther while  they  were  hot,  I  put  them  into  an  earthen  retort, 
glazed  within  and  without,  which  v/as  quite  impervious  to  air. 
This  I  placed  in  a  furnace,  in  which  I  could  give  it  a  very 
llrong  heat ;  and  conne6led  with  it  proper  veffels  to  condenfe 
and  colle^l  the  water  which  I  expe£led  to  receive  in  the  courfe 
of  the  procefs.     But,  to  my  great  furprife,  not  one  particle 

of 


relating  to  Air  dnd  IVatcr,  30  r 

of  moijlure  came  over,  but  a  prodigious  quaniity  of  alr^  and 
the  rapidity  of  its  produftion  aflonifhcd  me  ;  fo  that  1  had  no 
doubt  but  that  the  weight  of  the  air  would  have  been  equal  to 
the  lofs  of  weight  both  in  the  fcales  and  in  the^  charcoal ;  and 
when  I  examined  the  air,  which  I  repeatedly  did,  I  found  it  to 
contain  one-tenth  of  fixed  air,  and  the  inflammable  air,  which 
remained  when  the  fixed  air  was  feparated  from  it,  was  of  a 
very  remarkable  kind,  being  quite  as  heavy  as  common  air. 
The  reafon  of  this  was  fufficiently  apparent  when  it  was  de- 
compofed  by  means  of  dephlogiflicated  air;  for  the  greateft 
part  of  it  was  fixed  air. 

The  theory  of  this  procefs  I  imagine  to  be,  that  the  phlo- 
gifton  from  the  charcoal  reviving  the  iron,  the  water  with 
which  it  had  been  faturated,  being  now  fet  loofe,  affecled  the 
hot  charcoal  as  it  would  have  done  if  it  had  been  applied  to  it 
in  the  {oimoi Jham  as  in  the  preceding  experiments;  and  there- 
fore the  air  produced  in  thefe  two  different  modes  have  a  near 
refemblance  to  each  other,  each  containing  fixed  air,  both  com- 
bined and  uncombined,  though  in  different  proportions  ;  and 
in  both  the  cafes  I  found  thefe  proportions  fubjecl  to  variations. 
In  one  procefs  with  charcoal  and  fcales  of  iron,  the  firfi:  pro- 
duce contained  one-fifth  of  uncombined  fixed  air,  the  middle 
part  one-tenth,  and  the  lafl  none  at  all.  But  in  all  thefe  cafes 
the  proportion  of  combined  fixed  air  varied  very  little. 

Why  air  and  not  water  fhould  be  produced  in  this  cafe,  as 
well  as  in  the  preceding,  when  the  iron  is  equally  revived  in 
both,  I  do  not  pretend  perfe(ftly  to  underftand.  There  is,  in- 
deed, an  obvious  difference  in  the  circumftances  of  the  two 
experiments ;  as  in  that  with  charcoal  the  phlogifton  is  found 
in  a  combined  flate  ;  whereas  in  that  of  inflammable  air,  it  is 

loofe. 


^02         Dr.  Priestley's  ExperimcJits  and  Obfeivatlons 

looi'e,  or  only   united   to  water  ;  aiid  perhaps    future  experi- 
ments  may  difcover  the  operation  of  this  circumftance. 

There  is  fome  analogy  between  the  experinr-ent  of  the  calx 
of  iron  imbibing  inflammable  air,  and  the  iron  itfelf  imbibing 
dephioglfticated  air.  In  the  former  cafe  water  is  produced,  and 
in  the  Litter  Jixed  air.  However,  this  cafe  of  iron  imbibing 
dephlogiflicated  air  more  nearly  refembles  the  cafe  of  the  blood 
in  the  lungs  imbibing  the  fame  kind  of  air,  and  in  both  the 
cafes  as  dephlogifticated  air  is  imbibed,  fixed  air  is  formed. 
This,  therefore,  feems  to  be  a  confirmation  of  the  conclufion 
wliich  I  drew  from  my  former  experiments  on  blood,  viz.  that 
it  parts  with  phlogifton  in  refpi ration.  Only  1  would  now 
add,  that  at  the  fame  time  that  it  parts  with  phlogifton  it  takes 
in  dephloglfticated  air,  which  makes  the  cafe  perfe6tly  fimilar 
to  that  of  the  experiment  with  iron,  which  likewife  parts  with 
phlogifton  to  form  fixed  air,  at  the  fame  time  that  it  imbibes 
dephlogifticated  air  in  contact  with  which  it  is  fufed. 

I  propole  to  referve  for  a  future  communication  the  conti- 
nuation of  thefe  experiments,  containing  an  account  of  the  ap- 
plication of  the  fame  procefs  to  other  fubftances ;  but  it  may 
not  be  amifs  juft  to  mention  a  few  of  the  general  refults,  and 
thofe  which  have  the  neareft  connexion  with  the  experiments 
recited  above. 

After  having  tranfmitted  fteam  in  contact  with  charcoal  and 
iron  in  a  copper  tube,  I  propofed  to  do  the  fame  with  other  fub- 
ftances containing  phlogifton,  and  I  began  with  bones,  which 
were  burnt  black,  and  had  been  fubjected  to  an  intenfe  heat, 
covered  with  fand,  in  an  earthen  retort.  From  three  ounces  of 
bone  thus  prepared,  and  treated  as  I  had  done  the  charcoal,  I 
got  8-|0  ounce  meaiures  of  air,  with  the  lofs  of  288  grains  of 
water.  The  bones  wxre  by  this  means  made  perfedly  white, 
3  and 


rehithig  to  Air  and  Water..  ^o j 

and  had  loft  i  lo  grains  of  their  weight.  As  the  air  ceafed  to 
come  a  confiderable  time  before  all  the  water  had  been  tranf- 
mitted  through  the  tube  containing  them,  I  concluded  that  the 
air  was  formed  from,  the  phlogifton  contained  in  the  bones,  and 
fo  much  water  as  was  necefl'ary  to  give  it  the  form  of  air. 

This  air  differs  confiderably  trom  any  other  kind  of  inRam- 
mablc  air,  being  in  feveral  refpecl:s  a  medium  between  that 
from  charcoal  and  that  from  iron.  It  contains  about  one- fourth 
of  its  bulk  of  uncombined  fixed  air,  but  not  quite  one-tenth 
intimately  combined  with  the  remainder.  The  water  that 
came  over  was  blue,  and  pretty  ftrongly  alkaline,  which  muft. 
have  been  occafioned  by  the  volatile  alkali  not  having  been  in- 
tirely  expelled  from  the  bones  in  the  former  procefs,  and  its 
having  in  part  diflblved  the  copper  of  the  tube  in  which  the 
experiment  was  made. 

I  fubjecled  to  the  fame  procefs  a  variety  of  fubftances  thaf 
are  fald  not  to  contain  phlogiflon,  but  I  was  never  able  to  pro- 
ciwe  inflammable  air  by  means  of  them  ;  which  ftrengthens 
the  hypothefis  of  the  principal  element  in  the  conftitution  of 
this  air  having  been  derived  from  thefubfiance  fuppofed  to  con- 
tain phlogifton,  and  therefore  that  phlogifton  is  a  real  fub- 
flance,  capable  of  aiTuming.  the  form  of  air  by  means  of  water 
and  heat. 

The  experiments  above-mentioned  relating  to  Iron  were  made 
with  that  kind  which  is  inalleahk ;  but  1  had  the  fame  refult 
when  I  made  ufe  of  fmall  nails  of  caji  iron,  except  that  thefe 
were  firmly  faftened  together  after  the  experiment,  the  furfaces 
of  them  being  cryftallized,  and  the  cryftals  mdxing  with  each 
ether,  fo  that  it  was  with  great  difficulty  that  they  could  be 
got  out  of  the  tube  after  the  experiment,  and  in  general  the 
fclid  parts  of  the  nails  were,  broken  before  they  were  feparated 

from 


304         Dr.  Priestlky's  Experiments  and Ohfervations 

from  each  otlicr.     Indeed  the  pieces  of  malleable  iron  adhered 
together  after  the  experiment,  but  by  no  means  fo  firmly. 

Cafl:  iron  anneitled  (by  being  kept  red-hot  in  charcoal)  is 
remarkably  dillerent  from  the  caft  iron  which  has  not  under- 
gone that  operation,  efpeclallj  in  its  being,  to  an  extraordinary 
degree,  more  foluble  in  acids.  With  the  turnings  of  annealed 
call  iron  I  made  tlie  following  experiment.  From  960  grains  of 
this  iron,  and  with  the  lofs  of  480  grains  of  water,  I  got  870 
ounce  meaiares  of  inflammable  air,  and  tranfmitting  fleam 
through  them  a  lecond  time,  I  got  150  ounce  meafures  more. 
The  iron  had  then  gained  246  grains  in  weight,  and  the  pieces 
adhered  firmly  together  ;  but  being  thin  they  were  eafily  broken 
and  got  out  of  the  tube,  whereas  it  had  required  a  long  time, 
and  a  (liarp  fteel  inftrument,  to  clear  the  tube  of  the  caft-iron 
nails. 

Having  got  water  from  the  fcales  of  iron  and  of  copper  fatu- 
rated  with  dephlogift Icated  air,  by  heating  them  in  inflammable 
air,  it  occurred  to  me  to  make  the  fame  experiment  with  prcdi- 
pitate  'per  fe^  and  I  found,  that  the  moment  that  the  focus  of 
the  lens  fell  upon  this  fubflance  the  mercury  began  to  revive, 
the  inflammable  air  rapidly  difappeared,  and  water  was  formed 
on  the  fides  of  the  veffel  in  which  the  experiment  was  made.  For 
want  of  a  better  fun,  I  could  not  afcertain  every  circumfiiance 
relating  to  this  procefs ;  but  what  I  did  feemed  to  afford  a 
fufficient  proof  that  mercury  contains  phlogifton,  and  that  it  is 
not  revived  by  the  mere  expulfion  of  dephlogifticated  air,  as 
M.  Lavoisier  fuppofes ;  efpecially  as  ?w^.vW  ^/r  was  found  in 
what  remained  of  the  inflammable  air.  In  one  of  thefe  expe- 
riments 4.5  ounce  meafures  of  inflammable  air  had  difappeared, 
and  1.6  ounce  meafure  remained  ;  and  this  appeared  to  contain 
fome  dephlogiflicated  air' mixed  with  the  inflammable. 

4  Willing 


relating  to  Air  and  Water*  305 

Willing  to  try  the  efFeft  of  heating  iron,  and  other  fub- 
flances,  in  all  the  different  kinds  of  air,  without  any  particular 
expe£lation,  I  found  that  iron  melted  more  readily  in  vitriolic 
CiCid  air  than  in  dephlogifticated  air,  the  air  was  diminiflied  as> 
rapidly,  and  the  infide  of  the  veffel  was  covered  with  a  black 
footy  matter,  which,  when  expofed  to  heat,  readily  fublimed  in 
the  form  of  a  white  vapour,  and  left  the  glafs  quite  clean. 
The  iron,  after  the  experiment,  was  quite  brittle,  and 
mufl,  I  prefume,  be  the  fame  thing  with  iron  that  is  fid- 
phurared;  but  I  did  not  particularly  examine  it.  Of  feven 
ounce  meafures  of  vitriolic  acid  air,  in  one  of  thefe  experi- 
ments, not  more  than  three-tenths  of  an  ounce  meafure  re- 
mained ;  of  this  two-thirds  was  fixed  air,  and  the  refiduum 
of  this  was  inflammable.  I  had  put  three  of  fuch  refiduums 
together,  in  order  to  make  the  experiment  with  the  greater 
certainty. 

Having  tranfmitted  ^^<3W,  or  the  vapour  of  water,  througlr 
a  copper  tube,  I  was  willing  to  try  the  effects  oi  fpirit  of  wine 
through  the  fame  tube  when  red-hot,  having  before  procured 
inflammable  air  by  fending  the  fime  vapour  through  a  red-hot" 
tobacco-pipe^  In  this  cafe,  the  vapour  of  the  fpirit  of  wine- 
had  no  fooner  entered  the  hot  copper  tube,  than  I  was  perfedly 
sftoniflied  at  the  rapid  produ6llon  of  air.  It  refembled  the 
blowing  of  a  pair  of  bellows.  But  I  had  not  ufed  four  ounces-" 
of  the  fpirit  of  wine  before  I  very  unexpectedly  found,  that 
the  tube  was  perforated  in  feveral  places;  and'prefently  after- 
wards it  was  fo  far  deftroyed,  that  in  attempting  to  remove  itr 
from  the  fire  it  aftually  fell  in  pieces.  The  inlide  was  full  of  a 
black  footy  matter  refembling  lamp-black. 

Upon  this. I  had  recourfe  to  earthen  tubes ^  and  found,  that  by 
melting  coppfe'r  and  other  metals  in  them,  and  tranfmitting  the 

Vol,  LXXV*  R  x  vapour 


J 


3-06         Dr.  Priest  ley's  Experiments  and  Ohfct^callons 

vapour  of  f^urit  of  wine  in  contact  with  them,  differeiiffub- 
fiances  were  formed  according  to  the  metals  employed.  Thfe 
new  lubllances  hereby  formed  may  he  fa  id  to  be  the  feveral 
metals  lb  per- latu  rated  with  phlogifton,  and  may  perhaps  not 
be  improperly  called  the  charcoal  of  met  ah. 

That  this  appellation  is  not  very  improper,  may  appear  froiii 
thefelubftances  yielding  inflammable  air  very  copioufiy  when 
thev  are  made  red-hot,  and  the  fleam  of  water  is  tranfmitted 
in  contact  w^ith  them,  jiift  as  when  the  charcoal  of  w^ood  is 
treated  in  the  fame  manner.  The  detail  of  thefe  experiments 
1  referve  for  another  communication,  as  alfo  thofe  of  the  con- 
verfion  of  (pirit  of  wme,  tether,  and  o//,  into  different  kinds  of 
inflammable  air,  by  tranfmitting  them,  in  vapour,  through 
hot  earthen  tubes.  In  the  mean  time,  I  Ihall  think  myfelf 
happy  if  the  communication  of  the  preceding  experiments  (hall 
give  any  fatisfadion  to  the  Members  of  the  Society. 


P    O    S    T    S    C    R    I    P    T. 

BEFORE  I  clofe' this  paper,  I  wifli  to  make  a  few  general 
infer ences  froiti  the  principal  of  the  experiments  above-men- 
tioned, efpecially  relating  to  the  proportional  quantity  of  phlo- 
gifton  contained  in  /><?«  and  wafer. 

When  any  quantify  of  iron  is  melted  in  idephlogifticated  air, 
it  imbibes  the  greatefl  part  of  it,  and  gains  an  addition  of 
weight  very  nearly  eqilal  to  that  of  the  air  imbibed.  Thus  the 
abforption.  of  twelve  ounce  meafures  of  dephlogifticated   air 

2  gave 


relating  to  Air  and  Water,  ^oy 

gave  an  addition  of  fix  grains  to  the  piece  of  iron  which  had 
been  melted  in  it.  But  there  was  always  a  quantity  of  fixed 
air  produced  in  this  procefs  ;  and  on  the  fuppofition  that  this 
air  confifts  of  the  union  of  dephlogifticated  and  inflammable 
air,  it  proves  that  the  dephlogifticated  air  which  enters  the 
iron  expels  more  phlogifton  than  is  neceflary  to  conftitute  an 
cqnal  weight  of  water,  fo  ih^t  water  does  not  contain  fo  much 
phlogiflon  as  iron  ;   but  the  difference  is  not  very  confiderable. 

Admitting  Mr.  Kirwan's  conclufion,  viz.  that  loo  cubic 
inches  of  fixed  air  contain  8, 35  7  grains  of  phlogifton,  the.  1 3  ounce 
meafure  of  fixed  air,  which  (in  an  experiment  recited  in  thefe 
papers)  was  found  in  the  refiduum  of  feven  ounce  meafures  of 
dephlogifticated  air  abforbed  by  iron,  would  not  have  contanied 
more  than  .oi  grain  of  phlogifton,  or  about  .16  ounce  mea- 
fure of  inflammable  air.  Then,  as  the  abforption  of  12 
ounce  meafures  of  d^phlogifticated  air  occafioned  an  addition  of 
6  grains  to  the  weight  of  the  iron  which  had  abforbed  it,  the 
abforption  of  feven  ounce  meafures  mufl  have  occafioned  the 
addition  of  3.5  grains  to  the  iron  which  had  imbibed  it.  But 
the  fame  addition  of  weight  to  iron  given  hjj^eam  (which  car- 
ries its  own  inflammable  air  along  wdth  it)  would  have  expelled 
near  12  ounca  meafures  of  inflammable  air:  confequently, 
about  ten  ounce  meafures  of  inflammable  air  (or  the  phlogiuon 
requifite  to  form  it)  muft,  in  the  former  experiment,  have  been 
retained  in  the  iron>  in  order  to  compofe  the  water  which  was 
now  made  by  the  union  of  the  dephlogifticated  air  imbibed  by 
the  iron  and  the  phlogifton  contained  in  it :  and  therefore  the 
proportion  between  the  quantity  of  phlogifton  in  won  to  that 
which  is  contained  in  an  equal  weight  of  w^ater,  may  be  about 
12  to  10,  or  more  accurately  to  10.4. 

Had  no  fixed  air  at  all  been  found  in  the  refiduum  above- 
nientlGned,  it  might  have  been  concluded,  that  water  had  cori- 

R  r  2.  tained 


308  Dr.  Priestley's  Experiments  and  Obfervatkns 
tained  the  very  fame  proportion  of  phlogiflon  with  iron.  Since 
when  iron  that  has  been  faturated  with  dephlogifticated  air  is 
heated  in  inflammable  air  (in  which  procefs  an  equal  weight  of 
water  is  produced,  and  the  lofs  of  weight  in  the  iron  is  equal  to 
that  of  fuch  a  quantity  of  dephlogifticated  air  as  would  have 
been  one- h^] if  of  the  bulk  of  the  inflammable  air  which  difap- 
pears  in  that  procefs)  it  might  have  been  concluded,  that  one- 
fifth  of  any  quantity  in  water  had  been  inflammable  air. 

For,  neglecting  the  difference  between  the  weight  of  dephlo- 
gifticat-ed  and  common  air,  which  is  not  confiderable,  and  efci- 
mating  the  latter  -^-s^-^-th  part  of  water,  and  inflammable  air  at 
one-tenth  of  the  weight  of  common  air,  an  ounce  meafure  of 
dephlogiilicated  air  will  weigh  ,6  grain,  and  two  ounce  mea* 
fures  of  inflammable  air  will  weigh  .12  grain,  which  num- 
bers are  to  each  other  as  5  to  i  *. 

Though,  in  confequence  of  the  fmall  quantity  of  fixed  air 
Avhich  is  found  in  the  procefs  of  melting  iron  in  dephlogifli- 
•cated  air,  this  conclufion  is  not  accurate,  it  is  pretty  nearly 
fo ;  and  it  is  remarkable  that,  upon  tliis  fuppofition,  about  as 
;nuch  inflamxmable  air  is  expelled  from  iron  when  water  is  com- 

*  It  appears  from  the  prolccHtion  of  thefe  experiments,  that  the  water  which 
is  found  on  Jieating  tfee  leaks  of  iron  m  inflammable  air,  is  not  formed  by  the 
dephlogifticated  air  expelled  from  rhera  uniting  with  the  inilammable  air  in  the 
veiTel,  but  was  the  water  previonfl.y  contained  in  the  fcales^  which  is  made  to  quic 
its  place  by  the  introdutlion  of  the  phlogiflon  from  the  inflammable  air;  yet  that 
water  carries  out  with  it  not  much  lefs  phlogifton  than  was  taken  in  by  the  iron, 
3nd  a  little  more  mml  be  allowed  for  that  water  which  was  neCefTary  to  make 
inflammable  air,  and  which  could  not  enter  the  iron  when  it  was  revived  ;  fo  thar^ 
on  the  whole,  the  phlogifton  in  the  water  that  is  found  after  the  procefs  muft  be 
very  inearly  the  fame  quantity  that  is  imbibed  by  the  iron,  and  the  water  is  nearly 
the  fame  that  would  have  been  produced,  on  the  fuppofition  of  its  being  made 
from  dephlogifticated  air  exp'jiled  from  the  fcales  uniting  with  the  inflammable 
air  in  the  vcflel. 


relating  to  Air  and  Water*       '  509 

binecl  with  It,  as  the  water  itfelf  brings  along  with  it,  as  an 
eiTential  ingredient  in  its  compofition.  For  in  one  experiment 
296  grains  added  to  the  weight  of  a  quantity  of  iron  by  fteam, 
made  it  to  yield  about  1000  ounce  meafures  of  inflammable  air. 
This  would  weigh  60  grains,  and  one- fifth  of  the  296  grains 
of  water  will  be  59.2  grains.  Again,  267  grains  added  to  iron 
by  fteam  made  it  to  yield  840  ounce  meafures  of  inflammable 
air,  which  would  weigh  50.4  grains,  and  one-fifth  of  the  267 
would  be  53.4  grains. 

When  the  experiments  on  the  melting  of  iron  in  dephlo- 
gifticated  air  Ihall  be  repeated  on  a  larger  fcale,  which  it  will 
not  be  difficult  to  do  by  the  help  of  a  larger  burning  lens  than 
I  am  at  prefent  pofleffed  of,  it  will  be  eafy  to  reduce  thefe  cal- 
culations to  a  greater  certainty.  All  that  I  can  do  at  prefent  Is 
to  approximate  to  fuch  general  conclufionsas  I  have  mentioned ; 
■but  they  are  of  fo  much  confequence  in  philolbphy,  that  It 
will  certainly  be  well  worth  while  to  afcertain  them  with  as 
much  accuracy  as  poflible.  Nice  calculations  would  be  ill  be- 
^owed  on  the  imperfedh  data  which  I  am  as  yet  able  to  furnifh. 
Attention  muft  alfo  be  given  to  the  quantity  of  water  contained 
in  inflammable  air  from  iron  ;  which  not  being  yet  afcertalned 
is  not  confidered  in  thefe  inferences.  I  wifli  only  to  hint  in 
this  Poftfcript,  that  fome  important  conclufions  feems  to  be 
•nearly  within  our  reach. 


XNfi    OF    ^ARt    1.     OF     VX)U     LXtV* 


ERRATA. 


ycs^^e.  Line, 


VOL.     LXVII. 
289.      I'J-  dele  ihe  whoh  Ihe  except  ~-^  X p.     Whence, 


V  O  L.     LXXIV. 

32.      2b.  for  2      •OOOOOOOOOI,  ^read  2  — '0000000001, 
34.        8.  /ar  to  tangent,  read  to  cotangent. 

V  O  L.     LXXV. 

78.  2.  for  unequal,  read  unequal ; 

•94.  25.  /^r  20'  39'"  read  20"  39'" 

12Q.  lO.  Jor  Fl.  74,  r^«^  Fl.  74. 

170.  »0.  /?r  16-r^  read  16^1 

200.  15.  yiiy  in.  read  3. 

270.  14.  for  36°6  r^a^  36°,6