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Don Gronw.il Ltd.. London, N.2I. «•! 4310 



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54390 



LAMBERT, L.B. 

A five-part 
history of 
instruments. 









flstituto )£ /Ifouseo 2)i Storia Sella Scie^a 

A FIVE PART HISTORY OF INSTRUMENTS 

By L. B. LAMBERT, Hon.M.lnst.M.C. 



54390 



PART I AFTER THE FLOOD 2 

PART 2 MEASUREMENT TOPOGRAPHY AND CALCULATORS . 8 

PART 3 MAINLY TIME 16 

PART 4 MAINLY METEOROLOGICAL 23 

PART 5 MAINLY OPTICS, MAGNETICS AND STATICS ... 30 



Reprinted from July to November issues 
of Instrument Practice 1969 



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Front Cover: A meeting of the 
Accademia Del Cimento, founded in 
Florence, with the support of the 
Royal Medici family, in the 17th 
Century. Their discoveries were 
usually published as a body in 
order to avoid possible religious 
persecution of individuals. 



PART 1 AFTER THE FLOOD 



Most industries have grown from 
crafts whose history is almost en- 
tirely lost — just on archaeological 
indication here and there or some 
point inferred from literature giving 
an impression rather than a fact — 
but our instrument industry is more 
fortunate. In the beginning simple 
instruments were made for an 
extremely small number of philo- 
sophers striving to explain the 
working of the world around them. 
Little is known about these — most 
of the evidence disappeared during 
the Dark Ages. With the coming of 
the Renaissance the philosophers 
turned into scientists and the tempo 
of investigation was accelerated. A 
larger variety of apparatus was 
needed, the range of subjects in- 
creased, the number of workers 
grew and spread over much of 
Europe. What was little more than 
the hobby of a few individuals 
became part of the ordinary life of 
the time, both on land and sea, 
growing into an industry destined 
to increase in achievement and 
magnitude. Thanks to the records 
and practices initiated by the 
Florentines we know much about 

this progress that would otherwise have been lost. The history of this is voluminous — / have endeavoured to give an outline of 
that part of it centred on The Institute and Museum of the Story of Science, located in Florence, which I hope will be acceptable 
to the man who is interested but has not the time to dig it out for himself. Also, in spite of the enormous growth of technical 
complication, there may still be something to be gained, some prompting of an idea, some avoidance of an idea tried and 
abandoned and always the reminder of the value of simplicity that makes a little foray into the past a possible aid to the future, 
which, at the least, will be found interesting. 




Fig. I. The frontispiece of the Saggia di natural! esperienze — 
port of the records of the Accademia del Cimento 



THIS IS A story of a story, an account of an organization 
that has pieced together much of the history of the develop- 
ment of experimental science and has collected and 
preserved, with two major setbacks, the written and 
practical evidence of it -the Institute and Museum of the 
Story of Science — located in one of the centres from 
which spread the Renaissance. 

Somewhere near the beginning of the story there appeared 
Galileo, who adopted as his motto and guiding principle 
"Prove and reprove" — an ideal supported for a brief but 
brilliant period by the Accademia del Cimento, who also 
accepted Galileo's principle and embodied it in the 
frontispiece of their publication "Saggi di naturali esperi- 
enze" which is reproduced above (Fig. 1). After ten years 
this distinguished company was dissolved, but not before 
the practice of proving and reproving had spread to many 
other scientific intellectuals in Italy and elsewhere, having, 
indeed, laid the foundations of modern science. 

There is sometimes a tendency to bracket Leonardo da 
Vinci with Galileo, but there is a fundamental difference 
which is summed up by Dr. Maria L. R. Bonelli, Director 
of the Institute, in the following words: "One must then 
recognize that with respect to Galileo's more constructive 
work Leonardo's was sterile and inconclusive. Galileo, 
having a mind at once practical and speculative, talks like 
a scientist and has the order and clarity of a scientist in 
expository writing. Instead, Leonardo seems preoccupied 
with fast brief strokes, notes and vivid expressions, the 
stretch of numerous observations of things seen with the 
eye of an artist who cared little for rational and methodical 
co-ordination". Apart from the difference in mentality 
there was another — a difference in wealth. Galileo never 
had enough money to carry out all his ideas and experi- 
ments, and this was one of the reasons why he became one 
of the first philosophers to engage in the manufacture of 
instruments on a commercial basis. His father intended 
him for the medical profession, which is easily under- 
standable as the salary paid to a Professor of Medicine 
was 2000 scudi whereas that for a Professor of Mathe- 
matics was only 60 scudi. There is no means of evaluating 
the scudi, but if it be assumed that the medical profession 
lived reasonably well, the mathematician, or, as he fre- 
quently became, the physicist, had to have other sources 
of income to exist and follow his creative scientific urges. 
There were, of course, patrons, but never enough, in 
Galileo's case, to make him independent of financial 
worries. His conflict with the Inquisition during much of 
his life discouraged co-operation from those obliged to 
keep on the right side of the authorities. 

The habit of reasoned observation was undoubtedly an 
early characteristic of Galileo as he was only eighteen 
when he arrived at the law of isochronism. It may be a 
fable that this followed his study of a swinging lamp in 
Pisa Cathedral — the present one gives an excellent 
demonstration but it did not exist at the time attributed 
to his observations — but there is no doubt that he first 
applied the knowledge to a medical application, the 
measurement of pulse rate. This may have been the direct 
result of using his own pulse to time the period of the 
lamp cum pendulum. The practice was taken up by 
Santori, who is sometimes credited with the idea of the 
Pulsilogia. Many years passed before Galileo thought of 
applying the pendulum to the measurement of time as 
opposed to the measurement of rate. In spite of family 
pressure towards medicine Galileo tended more and more 
to physics and, while being mainly concerned with labora- 
tory experiments, he was something of an engineer — 
among other things he showed, in 1638, that the strength 




Fig. 2. Dr. M. L R. Bonelli— Director of the Institute and 
Museum of the Story of Science, Florence, with some of the 
instruments she rescued after the Arno flood 

of a wooden beam was proportional to its breadth and to 
the square of its depth. He started at Pisa in 1564 and then 
went to Padua until 1612. Following this he spent most of 
his time in Florence with excursions to Rome for, among 
other things, appearances before the Inquisition. Follow- 
ing these he was exiled to Sienna in 1633 and then sent to 
Arcetri, where he remained under house arrest until his 
death in 1642. 

In spite of the shortage of finance, the limitations of the 
then manufacturing techniques and religious persecution, 
this man established a remarkable amount of new know- 
ledge, properly recorded and available to others, earned 
the loyalty of such pupils as Viviani, and created the 
Galilean School which has had such a profound effect on 
subsequent scientific progress. A permanent reminder of 
the man, his work and his principles was set up in the 
Museum of Physics & Natural History in Florence. This 
was the "Tribuna di Galileo" and was centred on his 
objective lens and flanked by some of his instruments. In 
1929 it was moved to the Castellani Palace near the Ponti 
Vecchia and on the bank of the Arno. In the sixteenth 
century it was the home of the Castellani family. Later it 
housed the National Library, but this eventually moved 
and the basement, ground floor and the first floor became 
available. At this point we must introduce Professor 
Andrea Corsini who, for a long time, had dreamed of 
collating information and collecting together as much as 
possible of the scientific material existing in Italy, some of 
which, lacking a proper organization, was liable to 
deterioration because of insufficient interest and unsuitable 
storage accommodation. He started by organizing the 
National Exhibition of the History of Science which took 
place in Florence during 1929. This was a great success 
from the point of view of interest created, the material 
gathered together, and the fact that it came within the 
care of responsible people. When the exhibition was 



over the apparatus was distributed among the Institute of 
Rome, the University of the Military Geographic Institute 
of Florence, the Institute of Physics and the Observatory 
of Bologna University, but most of it remained in Florence 
which had made the most important contribution. There 
had previously been in that city a Museum of Antique 
Instruments opened in 1775 by Pictro Lcopoldo di Lorena, 
Grand Duke of Tuscany, under the direction of the Abbot 
Felice Fontana — of whom more anon. However, the 
museum languished somewhat because of lack of mainten- 
ance and also of space. In 1927 Andrea Corsini was able 
to obtain legal status for the Institute of History of Science 
as a non-profit earning body but supported by a State 
grant and voluntary contributions. This being so, he was 
able to collect all the exhibits of the old museum, including 
those of the Medici family, the university and others, all 
of which was concentrated in the Castellani Palace, and 
the subject of this account was then operating on a 
satisfactory and pleasing basis. From then on the contents 
of great historical value have been housed in well lit, 
warm, dry conditions and, above all, are the objects of 
great care and attention. It is not an open museum. The 
visitor is received at the main door and conducted round 
This gives the conductor a chance of explaining the exhibits 
and also ensures that they are not damaged — most of them 
are sufficiently accessible to be operated or handled, and 
the temptation to do this must be strong in many of us. 
However, some of the more important arc being provided 
with glass cases and special illumination. Of course this 
limitation of visitors is conducive to comfort and provides 
the opportunity of study without the interference of only 
half interested school children. 

During the early work in setting up this Institute Prof. 
Corsini was ably assisted by Dr. Maria L. R. Bonelli, a 
lady of great personal charm and energy who is a Professor 
of the University of Florence. She became the Director of 
the Institute in 1941 and has researched, written, travelled 
and lectured a great deal since then. 

While the collection has had the advantage of so much 
care and development, it suffered, as has been said, two 
major setbacks. The first of these was man-made during 
the campaign in Italy in the 1940/45 war. While there 
appears to have been either a compact between the bel- 
ligerants or some sort of gentleman's agreement, the 
Ponti Vecchia was the only bridge on that portion of the 
Arno that was not eliminated. It was unsuitable for tanks 
or heavy vehicles so it may well have been accepted as 
non-military. Had it become a target the Castellani Palace 
would have had small chance of survival. However, there 
were other bridges quite near, and the building did not 
escape entirely and some of the instruments were damaged. 
The instruments that survived were recovered, the building 
restored and, in spite of financial handicaps of post-war 
conditions, the museum was functioning again even if 
mourning its losses. 

The next unfortunate occurrence was not man-made. 
On the 4th November, 1968, the Arno burst its banks, 
Florence was inundated, the pressure of water forced 
open the Castellani doors, the basement filled immediately, 
and the ground floor was submerged under about five 
feet of swirling currents of muddy flood water. Dr. Bonelli 
was alone in the building. It must not be assumed that her 
staff had fled, leaving her to cope with the crisis — she 
occupies a beautifully furnished apartment so was on the 
premises while her assistants had not been able to reach 
them. Rescue work in the basement was impossible but 
Dr. Bonelli, working under water, recovered many of the 
smaller things but was forced to leave the heavier things 




Fig. 3. Treflers clock, made in 1692, operated by metal balls 
running down spiral grooves 



to their fate. All the rescue work came to an end with a 
further rise in level. Actually it reached a height of about 
8ft 6in. Fortunately some of the most precious and fragile 
items were on the first floor and well above flood level. 
Our illustration, Fig. 2, shows Dr. Bonclli with some of 
the things recovered outside after the waters had subsided. 
Once again came the agonizing work of surveying the 
scene, collecting partially damaged and completely wrecked 
apparatus and cleaning the building. This was followed 
by a programme of restoration, where possible, of the 
exhibits and the reconditioning of the building itself. 
Figure 3 shows a gravity operated timepiece as it originally 
was and as collected after the deluge. This is typical of 
the problems that faced the craftsmen repairing and 
reconstituting the damaged instruments. When the writer 
last visited the Museum there was no sign of catastrophe. 
If one looked very carefully a slight difference in the finish 
of the walls gave an indication of the highest water level — 
there is no plaque to record the occasion as in many other 
buildings. The decorations, the exhibits and the staff are 
all back to normal but. behind the scenes, there were still 
trays of parts, carefully identified and segregated, waiting 
their turn to have the attention of expert craftsmen. The 
work so far accomplished was pointed out, and it can 
safely be said that many of the damaged items will look 
just as good as they previously did but some, swirled 
around and repeatedly thrown against stone walls, are 
quite beyond repair. A few were washed outside the 
building and lost entirely. However, in spite of the losses, 
the museum still holds a unique collection of early instru- 
ments which we propose to cover in this and subsequent 
articles. 

Before proceeding with loosely classified descriptions, 
there arc two items which can be given separate treatment. 
One — the largest piece of craft showmanship that serves 
no other purpose beyond that of giving an idea of our 
planet and looking decorative. The other, which in its 
day was a really useful piece of apparatus, of which 
Galileo's artisans made at least sixty. The earliest known 
armillary sphere was made in China in 1276, but it has 
not survived. However, the one shown in Fig. 4 does still 
exist. It was made to the order of Ferdinando I de' Medici 
by his cosmographcr Antonio Santucci, who began on the 
4th March, 1588, and finished on the 5th May five years 
later. Santucci's team of painters and engravers decorated 
the whole surface, those parts not carrying pictorial 
designs being gilded. It is based on the Ptolcmic system 
and contains nine concentric spheres, each formed by the 
crossing of the equator, the two colurcs and the two polar 
circles having at the centre the globe of the earth on which 
are painted the continents. It can be given a rotational 
movement by means of a handle. The whole instrument 
has 82 armillarics or circles and, in addition, eight larger 
circles that support the horizon. The whole sphere is 
supported by the sculptured figures of the four winds and 
the horizon carries the coal-of-arms of the Medici family. 
Figure 5 shows the world as represented at the centre. 
There is a similar model in the library of the Escorial near 
Madrid which is believed to have been made by the same 
team. There is one major difference and that is size. The 
one in Florence is 3-80m high with a circumference of 
7-56m. The one in Madrid is much smaller but is still 
very imposing. As demonstration models they arc incorrect, 
as we now know that the earth is not the centre of the 
Universe. It has been suggested that they were more of 
the nature of scientific toys and, especially considering the 
high level of decoration, that they were really status 
symbols. Whether they were glorious pieces of ostentation 




Fig. 3a. Parts of Treflers clock as recovered after the Arno 
flood 



5 



Fig. 4. The armillary sphere made 
by Antonio Santucci which involved 
five years' work, terminating in 
1593 



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or not we cannot tell, but we can be sure that they were a 
natural outcome of the dawning wider interest in the world 
as a whole and the scientific explanation of how it works. 
This interest was no longer limited to necromancers, 
searchers after the "Philosophers' Stone" or alchemists, 
but was diffusing from the savants to the consciousness of 
many normal citizens. One practical result of this was 
the first nation-wide organization for meteorological 
observations brought into being by the Accademia del 
Cimento and employing methods and apparatus devized 
and supplied by that august body— the Royal Institution 
of the time. 

There may be doubts about the usefulness of the decora- 
tive armillarics but there can be no doubt about the utility 
of Galileo's "compass" or, as some prefer to call it "sector". 
The idea did not originate with him but he developed and 
expanded its capabilities. His military model was in great 
demand (Fig. 6). It is basically a hinged rule which can be 
opened out straight and used for linear measurement in 



the ordinary way. It can also be set at any angle between 
and 180 degrees with, in some models, the angle shown 
on an arcuate scale. The arms sometimes have cursors 
and compass points, but their main feature is the scales on 
the arms which, with the aid of dividers, enable many 
operations to be performed. One model, described by J. J. 
Fahie in his "Galileo" provides for the following: — 

"(1) Arithmetical lines — division of lines, solution of the 
rule of three, the equalization of money, the calcula- 
tion of interest. 

(2) Geometrical lines for reducing proportionately 
superficial figures, extracting the square root, 
regulating the front and flank formations of armies 
and finding the mean proportional. 

(3) Stereometrical lines for the proportional reduction 
of similar solids, the extraction of the cube root and 
for the transformation of a parallel piped into a 
cube. 



6 



(4) Metallic lines for finding the proportional weights of 
metals and other substances, for transforming a 
given body into one of another material and of a 
given weight. 

On the other side of the instrument are: — 

(5) Polygraphic lines for describing regular polygons 
and dividing the circumference into equal parts. 

(6) Tetragonical lines for squaring the circle or any other 
regular figure, for reducing several figures to one 
figure, and for transforming an irregular rectilinear 
figure into a regular one. 

(7) Joined lines used in the squaring of the various 
portions of the circle and of other figures contained 
by parts of the circumference or by straight and 
curved lines together". 

"There is joined to the compass a quadrant which, besides 
the usual divisions of the astronomical compass, has 
engraved on it a squadron of bombardiers and, in addition, 
transversal lines used for taking the inclination of the 
scarp of a wall". 

In the absence of definitions some of this is difficult to 
understand but the reference to "Bombardiers" is made 
clearer on another specimen, at present in the writer's 
hands, which is of doubtful origin but is of the Galilean 
type. It provides means of measuring the bore of cannon, 
the diameter of shot, and gives the weight of powder to 
"prove" a gun, the weight for normal firing, and the 
angle at which to lay the gun. All this, together with 
calculating scales and various formula, and the abbrevia- 
tion for the names of twelve sizes of cannon. 

Galileo never put his name or any other distinguishing 
mark on his products, although this was normal practice 
at the time. The great majority of his compasses and those 
based on his work have disappeared. Being small, of 
metal, and usually treasured, they were not nearly so 
liable to deterioration or full destruction as many other 
instruments. Some of them must still exist. Somewhere in 
the back of a drawer, or in an unused set of drawing 
instruments, or in a chest resting in an old attic, there 
might be one of Galileo's originals or one based on his. 
Either way the finder would have something of great 
interest and, possibly, of value in the monetary sense. 
Why not make a few enquiries among your friends and 




Fig. 5. The world as represented at the centre of another 
Santucci armillary 



relatives? The antique shop sometimes carries the invita- 
tion "Come in and see what your grandmother threw out". 
This might be icphrased "Have a looksee for what your 
grandfather did not throw out". 



Firenze. 1666-1667. 



Bibliography 

Saggi di naturali esperienze. 
Biblioteca Nazionale di Firenze. 

Celebrazione della Accadcmia del Cimento nel Tri- 
centenario della Fondazione. Presso la Domus Galileana. 
Pisa. 1957. 

The Revival of Ancient Science in Florence. Maria 
L. R. Bonelli. The Institute & Museum of the Story of 
Science. Florence. 

Note About Galileo's Instruments. Maria L. R. Bonelli. 

The Armillary Sphere in the Library of the Escorial in 
Madrid. Maria L. R. Bonelli. Pergamon Press, 1968. 

Galileo -His Life and Work. J. J. Fahie, M.I.E.E. 1903. 
John Murray, London. 




Fig. 6. One of Galileo's 
"military compasses" or 
sectors 



PART 2 MEASUREMENT, TOPOGRAPHY AND CALCULATORS 



This is the second of a series of 
articles giving some of the early 
history of instruments, more particu- 
larly that part of it associated with 
the Galilean School and its work 
now preserved in the Institute and 
Museum of the Story of Science at 
Florence — the centre from which 
spread the Renaissance. 

Somewhere near the beginning of 
the story there appeared Galileo, 
who adopted as his motto and 
guiding principle "Prove and re- 
prove" — an ideal supported for a 
brief but brilliant period by the 
Accademia del Cimento, who also 
accepted Galileo's principle and 
embodied it in the frontispiece of 
their publication "Saggi di natural! 
esperienze" which is reproduced as 
the heading illustration linking this 
series of articles. In a time when 
It is commonplace to measure in 

nano seconds it is strange to reflect that the recent moon walks are only the logical culmination of thework of men like James 
Fergusson who constructed an Orrery of the Sun and its planets in 1773. 




IT IS GENERALLY accepted that the first measurements 
made by man were of length, followed, no doubt, by that 
of simple accessible height. Length of any surface that 
could be traversed was easy but heights out of body reach 
were more difficult and progress in this direction was 
delayed for centuries or, more probably, millenniums. The 
first means were anthropometric and, therefore, available 
to all. Short distances in the horizontal could be compared 
with the length of the human foot. Longer distances could 
be paced out- -the "pace" being a double stride. This 
came to be accepted as 5ft 3in. One thousand such paces 
were a '"mille", which was soon modified to the "mile". 
Short distances at, say, table level, would be more con- 
veniently measured in "cubits", the length from the elbow 
to the tip of the middle finger, or, the "span", the distance 



between the tip of the thumb and that of the little finger 
with the hand extended. The height of animals was ex- 
pressed in "hands", the width of the hand when held flat. 
Even if the definition of these units was accepted as being 
those of normal individuals, the approximation is very 
loose. The cubit, for example, could vary from 18 to 22in 
and amount to a spread of 18%. The hand can vary a 
similar amount, but it is of course still retained in connex- 
ion with horses. Presumably the absence of a really fixed 
point for the upper limit and the general acceptance of 
the hand as being four inches are the reasons for its contin- 
ued use. Obviously the loose approximations of anthropo- 
mctrical means of measurement would not be acceptable 
when man started trading. It is easy to visualize a large 
body being employed to buy and the smallest one available 






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F/g. /. Prehistoric rules showing influence of anthropological 
basis. "Crown Copyright. Science Museum, London". 

to sell. The establishment of some sort of defined rule was 
inevitable. Figure 1 shows an early example in which the 
anthropological influence is still strong. However, they at 
least provided a means ol" defining length on a basis which 
would clearly show the amount offered by the vendor and 
accepted by the vendee. The rules gradually became more 
sophisticated but still lacked a uniform basis, and although 
the spread of variation decreased, they were arbitrary and 
limited to one locality. Some of these early types are in 
the possession of the Institute and are shown in Fig. 2. 

In the course of time most countries arrived at a basis of 
measurement that was standardized locally and had a 
legal status. In the case of this country we carried on the 
anthropometric connection and continued to refer to the 



"foot". It is interesting to speculate as to how long after 
we have legally adopted the metric system we shall still 
find it necessary, especially in legal property matters, to 
refer to this archaic expression. However, it was obviously 
desirable to arrive at a universally acceptable unit of 
length and some fundamental basis was sought. Attention 
was once again directed to the Earth's meridian and 
efforts made to establish its dimensions accurately. 
Arising out of this, a series of measurements made by 
Gian Domenico Cassini and his son Jacques determined 
that the dimension of the degree of latitude decreased 
with the approach to the Poles and deduced that the dia- 
meter of the Earth at the equator was greater than that of 
the Poles. This was confirmed by the French, led by La 
Condamine, who carried out a long series of measurements 
in Lapland and Peru between 1735 and 1745. As an 
essential part of this work they made a very accurate 
measurement of a base line — the famous "Peru Line". 

The French had for some decades been active in world 
survey and by 1682 had defined with good accuracy the 
latitude and longitude of 24 places on the French coast. 
Other nations also operated in this field and by 1691 the 
number in Europe had increased to 83, while on a world- 
wide basis the total was 109. All of this depending on the 
continued development of instruments, particularly 
improvement in accuracy and repeatability. 

Following the establishment of the dimension of the 
Earth's meridian the French took one ten-millionth of its 
quadrant and called this the "Metre". This was put into 
practical form as a bar of platinum-iridium (90% — 10%) 
which could be regarded as stable over a very long period 
or time. The original standard is preserved in the Museum 
of Sevres near Paris. Except in scientific circles it has never 
become universal, but those countries which recognized it 
were provided with copies and one of these, Fig. 3, is still 
maintained in Florence, The one-time impression that this 
was the ultimate has, of course, been disproved, and the 
standard is now based on the wavelength of light. 

The increase in knowledge of the Earth's shape and 
dimensions stimulated the production of more complete 
and accurate maps which led to more sophisticated drawing 
instruments, many of which have survived. One of the 
simplest sets in the possession of the Institute was used at 
the end of the 17th century. It contains two parallel rules, 
a folding rule, an instrument for describing ellipses, a 
compass, and various accessories. A more elaborate 




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Fig. 2. Early metal and ebony rules 



9 




Fig. 3. Copy of the original platinum standard, now preserved in Florence 



collection, made before 1776 and housed in three trays 
contained in a case simulating a book, is shown in Fig. 4. 
In the first tray is (1) an instrument for the measurement of 
declination which consists of a calibrated circle and four 
alidades, a tangential rule in three foldable parts for the 
measurement of distance, a magnetic compass and, on the 
back, two graduated scales for height measurement. 
Quite an elaborate piece of apparatus which would puzzle 
the average modern draughtsman, (2) a square frame 
with divisions for heights and a graduated quadrant, 
(3) a compass of four arms, two of which rotate about a 
cursor that traverses a third arm in such a manner that it 
always bisects the angle formed by the other two. In the 
second tray there are (1) a proportioning compass of the 
Galilean type, (2) a polymctric rule, (3) weight for a pendu- 
lum or plumbob, (4) adjustable pen compass, (5) foldable 
square rule. The third tray contains dividers and compasses 
of various types. 



Figure 5 shows part of a collection of instruments made 
by Christophorus Schissler which was taken to Florence by 
Prince Mattias, brother of Ferdinando II dc'Medici. The 
collection comprises: (1) several magnetic compasses, (2) 
four graduated rules with cursors and removable alidades, 
(3) graduated rule inscribed H.I.S. 1581, (4) a sun clock 
with cursor and a steel pendulum inscribed C.H.R.S.S. 
1596, (5) quadrangle formed of four rules graduated in 
110 equal parts, (6) special pen, (7) small quadrant with 
scale, (8) various accessories to facilitate measurements. 
Mention must also be made of the beautiful compass due 
to Schissler shown in Fig. 6, with its accessories. This is 
associated with "The Squaring of the Circle, the Science of 
Residuals, the Compass and the Rule" by the brothers 
Fabrizie and Gasparo Mordcnte, published in Amsterdam 
in 1591. 

The first instrument for the measurement of height 
seems to have been that known as "Jacob's Staff". It was 




Fig. 4. Comprehensive set of 
drawing instruments in an unusual 
type of case 



10 



Fig. 5. Collection of drawing 
instruments taken to Florence by 
Prince Mattias 




followed by the astrolabe, which was used for several 
centuries to measure angles in both the vertical and hori- 
zontal planes. While it was mainly employed for astro- 
nomical purposes, it was also used for topography. In its 
simplest form it consisted of a metal disc with graduations 
round the periphery and an alidade, or pointer, which 
could be aligned with a given object and the angle measured. 
It was, during the centuries of its use, elaborated both in 
design and application including the "rete", pinhole or 
other form of sights and cursors on the alidade. Its 
origin is uncertain. It may have been used by Hipparchus, 
but it is more probable that it had its beginnings in the Alex- 
andrian School about the middle of the second century. 
The Arabians certainly employed it at the height of their 
culture. The Persians produced some splendid models 
and it is known to have been used by the early marine 
explorers including Henry the Navigator, who ventured 
far enough from his native Portuguese shores to discover 
the Azores and, subsequently, set up an observatory at 
Sagrcs, near Cape St. Vincent, where more accurate tables 
of solar movement were determined. There is doubt about 
the age of some of those surviving; the year 900 is a possi- 
bility, but most of them arc of a much later date. It 
flourished until the 17th century following which it was 



gradually replaced by the quadrant. The fully developed 
astrolabe, an example of which is shown in Fig. 7, consists 
of the "madre" which is a thick disc of metal recessed to 
take the "timpani" on which arc cut the lines of height and 
azimuth, other graduations or star maps. The timpani are 
changeable and keyed for correct location. Above and 
part of the madre is the "throne" which carries a ring for 
the suspension of the instrument. Working over the face 
of the timpani is a fretted disc called the "retc", or net, 
which is virtually a complex of indices that point to the 
position of stars and a circle that represents the zodiac. 
These three circular members are held together by a 
pivot in the centre on which turns the alidade or pointer. 
Very often the reverse is provided with more graduations 
and a second alidade. The material employed was usually 
brass although iron is known to have been used. It was 
always made heavy enough to ensure that it hung vertically 
— particularly desirable when used for navigational pur- 
poses. Some of the Arabian models were set with precious 
stones. The possession of, and the ability to use, this 
instrument must have been a matter of personal prestige 
which, in the case of the Arabian models, may account for 
the extra embellishment. The names of the makers of 
astrolabes have almost entirely disappeared into historical 



Fig. 6. Compass made by 
Christophorus Schissler about 1591 




11 



vacuum but some are known, and among these is that of 
Gualtiere Arsenio di Lovinic, a nephew of the Dutch 
mathematician and geographer — Gemma Rainer (1508- 
1555) who first defined the principle of triangulation. 
Arsenio gave his astrolabes a small magnetic compass to 
enable them to be used for ascertaining horizontal angles. 
The astrolabe shown in Fig. 7 is one of Arsenio's. On the 
reverse, under the quadrant of the shadow, is given the 
name of the originator and the date of manufacture. 
Arsenio seems to have built up quite a business for this 
and other types of instruments, but his success was cut 
short by the spread of the European war that devastated 
the Low Countries in 1578. Round about the same time 
similar work was being done in Italy under the aegis of the 
Tuscan family of Delia Volpaia. Figure 8 shows an earlier 
astrolabe associated with Galileo, and used mainly for 
topographical purposes, which is also in the collection at 
Florence. Our own Geoffrey Chaucer, of "The Canterbury 
Tales", was also something of a scientist and wrote a 
"Treatise on the Astrolabe" which is one of the earliest 
technical works written in the English language, and is 
considered one of the best and most lucid accounts of 
the astrolabe. The early writing was, of course, in Latin, 
but Chaucer took a step towards making knowledge 
available to a larger section of the community. 

Associated with the astrolabes and drawing instruments 
are other devices for cartography and laying out building 
sites and so forth. One of these, a "distance measurer", is 
shown in Fig. 9. It was constructed in 1557 by Baldassarre 
Lanci da Urbine and is based on simple trigonometry. It 
was also used as a Graphometer. Another device for the 
same purpose, constructed by Erasmus Habermel, was 
considered the most perfect of the older topographical 
instruments as it had a magnetic compass for orientation, 
could be mounted on a tripod, and fixed in station (Fig. 
10). Shortly after this, Leonard Digges produced his book 
"Theodolitus" in London and Galileo produced his tele- 
scopes giving rise to the modern conception of the 
theodolite. 

In Fig. 11 we show the topographical device made by 
Antonio Bianchini in Venice in 1564. This was known as 
the "Grand Rule of Ptolemy". The numerous operations 




Fig. 7. Front of astrolabe made by Arsenio di Lovinie about 1570 

of which it is capable are detailed in Codice 82 -preserved 
in Florence. There are sights on both arms, one pair of 
which can be folded down so that one arm can traverse 
the other. It embodies a sun clock equatorial for latitudes 
between 20 and 50 degrees, a magnetic compass, a wind- 
rose, and various other scales associated with the measure- 
ment of distance. The windrose is a rosette-like diagram 




Fig. 8. Astrolabe associated with 
Galileo and primarily intended 
for use in or near the horizontal 



12 





Fig. 10. The "most perfect" topographical instrument of its 
time. Made by Erasmus Habermal 



Fig. 9. A topographical instrument made in 1557 by Baldessarre 
Land da Urbine 




Fig. 12. Odometer, probably made by Schissler about 1590 




Fig. II. The Grand Rule of Ptolemy 



13 




Fig. 13. Adding machine, due to 
Tito Livie Burattini, presented 
to the Grand Duke Ferdinando II 
de' Medici prior to 1659 



giving the points of the compass and showing the relative 
frequency and strength of the winds for a given geographical 
area and period of the year. 

Used in conjunction with these topographical instru- 
ments was a device due to Erone of Alexandria, and 
which measured distances much more accurately than the 
anthropometric methods referred to earlier. This was the 
Odometer, or, as a comparatively new nation in these 
matters prefers, Waywiser. This is often seen in London 
and elsewhere these days in connexion with the measure- 
ment of 'bus routes. It consists of a wheel which is 
traversed over the distance to be measured. At every 
rotation a movement is transmitted to a system of gears 
carrying figures which show the total number of revolu- 
tions made. Obviously the diameter of the wheel can be 
calculated for a convenient distance for each rotation. 
The instrument in the Institute, Fig. 12, was probably 
made by Schissler and is well over four hundred years old. 

The pedometer was also used in the 16th century. The 
dial was fastened to the operator's belt and a cord linked 
with his foot. Each step operated a ratchet device so that 
the number of steps was recorded. The "pace" was still 
a double stride. 

While the Odometer seems to have been the first auto- 
matic totalizer widely used, the earliest known device was 
recovered from a wrecked ship off the coast of Greece. 
Although badly corroded it was clearly a geared mechanism, 
and the disposition of the gears suggested that it was part 
of a totalizer. This is attributed to somewhere between 
100 BC and 200 AD and it must have been a rare piece of 
instrumentation at that time. We must hope that it did 
not contribute to a navigational error resulting in the loss 
of the vessel that carried it. It is possible that the first idea 
for a calculating machine, as such, was contained in a 
letter sent by Kepler to the German astronomer Wilhelm 
Schichard. However, the apparatus was never made. A 
machine capable of addition was made by Pascal in 1652 
and it is said that he made fifty before producing a success- 
ful one. It was followed by one due to our Samuel Morland 
and made in London during 1664. The names of the 
craftsmen who actually made it arc engraved thereon — 
H. Sutton and S. Knibb. Like Pascal's machine it could 
only add, but some multiplication could be done by the 
necessary number of additions. It is contained in a fine 
wood case and uses 55 wheels of silver with a further 17 of 
silvered brass. The specimen, now in the Institute at 



Florence, was presented in 1679 to the Grand Duke 
Cosmo III. In 1673 Leibnitz described a machine capable of 
multiplication which, for technical reasons, could not be 
manufactured at the time. However, it was made in 1923 
on the basis laid down by Leibnitz. 

A less well-known machine, Fig. 13, was given by Tito 
Livie Burattini to the Grand Duke Ferdinando II 
de'Medici. This is known to have existed in the "Guarda- 
roba Mcdicea" in 1659. 

Some two hundred years later the machine shown in 
Fig. 14 was constructed by Tito Gonnella and some of the 
characteristics of the modern office machine begin to 
appear, most obviously, the numbered keys. 

Another piece of apparatus, due to Samuel Morland, is 
shown in Fig. 15. It was made by Johannes Marke in 
London during 1670. This provides means of determining 
the sides and angles of triangles, and arriving at other 
trigonometrical results without actually carrying out any 
calculations. The main dial, two smaller dials and the 
rules are of silver. This is said to be capable of saving a 
great deal of calculating time. 

A further device directed at arriving at positional 
information while avoiding routine calculation is the 




Fig. 14. A later adding machine due to Tito Gonnella 



14 



Fig. 15. Trigonometrical calculator 
due to Samuel Morland 




Orrery, so called in honour of Charles Boyle, fourth Earl 
of Orrery, who financed the manufacture of the first model. 
It is based on the Copernican system and, therefore, unlike 
the armillaries, holds good today. The one in Fig. 16 was 
constructed in London in 1773 by James Fergusson. It 
has the sun at the centre of the Universe. Around it turn 
the planets Mercury and Venus and also the Earth, around 
which rotates the Moon. Not included in the demonstration 
are the other planets — Mars, Jupiter and Saturn. The 
device is operated by hand to show the relative move- 
ments of the system and their position on a given date. 
This can, we submit, be regarded as the germ from which 
all space travel calculations have grown. 



Bibliography 

Enciclopedia Mondadori delle Scienzc. S4. Edgardo 
Macorini. Florence. 1968. 

A History of Technology. Editor Charles Singer. 
Oxford. 1957. 

Theodolitus. Diggis. 1571. 

Treatise on Astrolabes. Chaucer (1391). W. W. Skeat. 
London. 1872. 

Astrolabes of the World. R. T. Gunter. Oxford. 1932. 

Tartaglia. Questi c invention!. 1524. 

Scientific Instruments in Art and History. H. Michel I. 
Barrie and Rockliff, London. 



Fig. 16. Orrery made in 1773 by James Fergusson 




IS 



PART 3 MAINLY TIME 




This is the third of a series of 
articles giving some of the early 
history of instruments, more particu- 
larly, that part of it associated 
with the Galilean School and its 
work now preserved in the Institute 
and Museum of the Story of Science 
at Florence — the centre from which 
spread the Renaissance. 

Somewhere near the beginning of 
the story there appeared Galileo, 
who adopted as his motto and guid- 
ing principle "Prove and reprove" — 
on ideal supported for a brief but 
brilliant period by the Accademia 
del Cimento, who also accepted 
Galileo's principle and embodied it 
in the frontispiece of their publica- 
tion "Saggi di naturali esperienze" 
which is reproduced as the heading 
illustration linking this series of 
articles. The second is defined as 
the duration of 9, 192, 631, 770 

cycles of the radiation associated with a specified transition of the cesium atom. It is suprising that although the sophistication 
was missing the Renaissance engineers and scientists managed such accuracy and repeatability. 



"COME AND DINE when your shadow is ten times as 
long as your foot." This is said to be an invitation given 
by Aristophanes and, as it was given in a sunnier clime 
than ours, it may well have been a good enough definition. 
The length of the sun's shadow, cast by any fixed object, 
was an accepted method for measuring time for many 
thousands of years. At the equator it needed no qualifica- 
tion, but progress towards the Poles introduces an increas- 
ing variation over summer and winter, and local corrections 
are necessary. These were worked out in many places 
including, in this country and around the year 700, by the 
ecclesiastical historian and scientist, Bedc. He compiled 
tables giving the length of the shadow of a six foot gnomon 
for nine in the morning and three in the afternoon, at two 
week intervals, for the latitude of 55 degrees — that of 



Jarrow Monastery. It is nice to think that his data enabled 
a wooden stave to be calibrated for the seasonal changes 
so that the pilgrim who used one to assist his walking or 
in self-defence could also use it as a sort of portable clock, 
providing, of course, that the sun co-operated. One of the 
objects of his travel, Canterbury, has a sundial with scales 
for April to September but not for the winter months, 
presumably because it was recognized that they would not 
contain enough sunshine to make any more scales worth- 
while. 

In the course of time the direction of the shadow came 
into use. This type needs orientating to the North, which 
was first done in relation to the Pole Star. Later the intro- 
duction of the magnetic compass not only facilitated this 
but also made possible portable sundials, or sun clocks, 



16 




Fig. I. Some polyhedral sundials with one cubical type embodying a magnetic compass 



which were often beautifully made and some of which 
employed precious metals. We have, therefore, two main 
types of sundials — one using the length and the other the 
angle of the shadow. Some did employ a combination of 
both. All three are classified as "Gnomons". 

The rod or staff which formed the gnomon itself was, in 
the early days, placed vertically, but with increased know- 
ledge it was later set at an angle to the sun to compensate 
for the change in the angle of the earth in relation to the 
sun. 

Another type of sundial employs a beam of sunlight 
which can be via a small aperture to the inside of a cylinder 
and in portable form, or by means of an "oculus" in the 
south transept of our orientated churches. The oculus is 
usually embodied in the construction of a window and 
sometimes in the design of the stained glass therein. The 
time indications, or, more often, the noonline, are incorpor- 
ated in the floor pattern so there is no point in looking 
for something like an instrument. However, this arrange- 
ment does provide, in effect, a long scale and enables the 
moment of noon to be determined with good accuracy, 
which brings us to the next point. 

During the latter part of the period so far covered other 
means of telling time had been developed clepsydras, 
sandglasses, clocks and even watches but, until the days of 
telephony and radio, these were still checked locally 



against sun time. As, in most cases, the only time indication 
available to the ordinary people was the church apparatus; 
the oculus in the south transept must have been of particu- 
lar value. For some long time after mechanical clocks were 
readily available, the manufacturer would supply a sundial 
to set them by. The early church timing was signalled by 
bells or "cloches". An example of this is the apparatus in 
Salisbury Cathedral. Installed in 1386 and modified more 
than once, it still gives only an audible indication of the 
passing hours. In the course of time, dials with hands 
appeared and "cloche" was corrupted to "clock". 

A later device, of which there is an example in the 
Institute and Museum of the History of Science, is the 
noon gun fired by the sun's rays focused on to the powder 
fuse by a lens, or, as it was usually called in this connexion, 
burning glass. The burning glass is by no means completely 
a thing of the past. Substitute a glass sphere for the lens 
so as to provide for the vertical and horizontal changing 
angles of the sun's rays and add an arcuate strip of card 
with means of holding it round part of the sphere, and you 
have a current type of sunshine recorder which burns its 
own record and provides its own time/duration measure- 
ment. While there are more sophisticated instruments for 
research purposes, the glass sphere is still standard for 
routine meteorological use. 

Among the early means of indicating time preserved in 



II 




Fig. 2. Multi-latitude sun "clock" with magnetic compass- 
made by Hans Ducher 



the Institute arc portable sundials of polyhedral and 
triangular prism form which arc highly decorative and 
which solved the problem of orientation before the use of 
the magnetic compass (Fig. I). If they are rotated until all 
the gnomons show the same time they arc correctly placed, 
and the time may be read. 

Figure 2 shows a sunclock made in ivory by Hans 
Ducher. This is arranged for latitudes of 42, 45, 48, 51 and 
54° and for the localities detailed inside the cover. It 
contains a magnetic compass for orientation and the main 
time scales arc located round the compass. The gnomon 
is in the cover above the scales. This type, when intended 
for use by Muslims, has a line indicating the direction of 
Mecca. 

A further variation for a sundial is shown in Fig. 3. 
The cylindrical body carries a gilded gnomon. Around 
the cylinder are scales for every month in the year. This 
was dedicated to Francesco I de' Medici. 

An unusual type, reminiscent of the Roman scaphe, is 
that shown in Fig. 4. It is obviously intended to be clamped 
to a rod and, unlike those so far described, is weatherproof, 
being made entirely of metal. The gnomon is located at 
approximately 40" through the side of the cup and throws 
its shadow on one or more of the three scales parallel to 
the three slots cut in the cup. The small dimensions of the 
cup in relation to the diameter of the gnomon make this 
device very approximate and it can only be read with an 
error of some thirty minutes. 

Another all-weather type, Fig. 5, is carved from a 
block of limestone and is a bit of a mystery. It comprises 
four pairs of scales on the sides with one on the top surface. 
Its principal gnomon is missing but the edge of each 
cylindrical cavity will throw a shadow for part of the day. 
The object of the horizontal cylindrical hole is not apparent, 



unless it was intended to have an oculus suitably disposed 
to give a noonline inside the cylinder. 

Space does not permit doing full justice to this part of 
the collection. Sundials are many and various as the 
result of the combined efforts of artist, scientist and 
craftsman. In this country we think of them more as 
garden ornaments, but the portable forms of those that 
followed the Renaissance have become collectors' pieces 
and of world-wide interest. 

The moon was also used for time determination but 
suffered from the disadvantage of a nightly correction of 
some fifty minutes and its virtual disappearance from the 
sky for some nights in each month. However, devices — 
usually known as "Nocturnals" — were made that were 
of practical use. One of these is similar to the folding 
assembly shown in Fig. 2 but in place of the gnomon it has 
an aperture through a rotatable disc. This is turned until 
a spot of moonlight is brought to a datum line, when the 
time can be read on a somewhat complex scale arrangement. 
Another type, intended for permanent installation, is 
shown in Fig. 6. This can be used on both a solar and lunar 
basis. The square plate has two locating projections at the 

► 

Fig. 3. Cylindrical sundial with seasonal time lines 




18 




Fig. 4. Cup type sundial 



Fig. 5. Multiple sundial carved in limestone 




base and carries a multiplicity of excellently divided 
graduations. Pivoted in the centre is a contoured disc cut 
away to give a sector applicable to day and a second I'or 
night use. The alidade is hinged so that it can be set in the 
desired position. It was made in brass by Gcorg Zorn 
of Augsburg, but is now in the Institute's collection. 

A somewhat similar instrument is shown in Fig. 7. 
This is due to Gcrolamo dclla Volpaia (1568). Constructed 
of brass, it consists of three discs and an alidade all pivoted 
on the same centre. With the instrument suspended in the 
vertical, the operator sights the Pole Star through the 
centre aperture and rotates the alidade until it lines up 
with the two "pointer stars" in Ursa Major (the Great 
Bear). The time can then be read visually or, alternatively, 
the hour counted off from the twenty-four teeth cut in 
the uppermost disc for the purpose. The device includes a 
zodiacal calendar. 

Apart from the utilitarian types mentioned there were 
so called "Universal Clocks" arranged for solar and lunar 
use and embodying calendars, stellar maps and zodiacal 
information. They were always very handsome pieces 
and must have cost a great deal of money, particularly 
with regard to the limitations of the means of production 
then available. One of these, which occupied Giovanni di 
Dondi for the sixteen years ending 1362, gave the move- 
ments of the sun, moon and five planets with "surprising" 
accuracy, plus a perpetual calendar for the movable feasts 
of the church's year. His lunar train employed gear 
wheels of oval contour and irregularly spaced teeth which 
must have presented quite a problem in marking out and 
filing by hand. A "Universal Clock" in the collection at 
Florence is shown in Fig. 8 and was made by Mans Christop- 
horus Schisslcr. This combines an astrolabe with solar, 
lunar and stellar data while a calendar is contained in the 
base, pivoted at one end, so that it can be swung out for use. 
We have previously referred in some detail, in the 
second article of this series, to the Astrolabe, in connexion 
with the measurement of topographical height. However, 
its main use was astronomical, where by solar or lunar 
angles it permitted the measurement of time, facilitated 
study of the movements of celestial bodies, assisted the 
navigator as well as the surveyor or cartographer. It was 
eventually replaced by the quadrant, which had the same 
variety of uses. As a sighting of a celestial body or a 
building could not involve an angle of more than ninety 
degrees, the quadrant could do all in this direction that 
the astrolabe could do with, when desirable, some reduction 
in weight. They were usually mounted on a wall or pillar 
or, alternatively, means were provided for locating them 
against a prepared surface which was levelled and orien- 
tated according to requirements. They could, of course, 
be used with both sun and moon. The later models had a 
magnetic compass to assist surveying and cartography. 
On the reverse or "dorsum" they often had means of 
making graphical calculations or curves to facilitate 
dividing the total period of daylight into twelve equal 
periods, which was at one time a common practice. 

The quadrant shown in Fig. 9 is said to have been made 
in Naples during 1553. On one side it has a zodiacal calen- 
dar, the names of the constellations, angular scales and an 
alidade. On the reverse there is a square graticule for the 
declination of various stars, and a rectangular one for 
solar calculations. It also has the latitudes of some Scan- 
dinavian cities. 

Another quadrant of interest was made by Giambattista 
Giusti who was associated with Gregorio XIII and the 
reformation of the calendar in 1582. It has solar lines, a 
magnetic compass, a windroso and a hinged member for 



19 



the gnomon. On the reverse, it has the "magic" square 
of numbers: — 

492 
357 
816 
which, of course, adds up to 15 in any direction. The 
reason for this piece of "magic" is not apparent. 

An unusual quadrant was made in Rome about 1550. 
The body was of iron with the graduations, symbols and 
curves inlaid in gold and silver. A further variation of 
material was employed by Stefane Buonsignori of Florence 
who used ebony for the main base with brass circles carrying 
the graduations, calendar, zodiacal signs and providing 
for some geometrical calculations. It also had a magnetic 
compass let into the ebony base. 

To most of us the use of the sun to tell us the time seems 
reasonable but using the moon seems rather remote. 
However, it should be remembered that the great Captain 
Cook, for his first voyage in 1768-71, had only "that great 
natural chronometer presented by the moon in her orbital 
motion round the earth". 

While the quadrant, in one or the other of its many 
forms, continued in general use, its employment as a time 
device diminished during the eighteenth century as mech- 
anical clocks were developed from audible signallers of 
fixed time intervals to continuous visual indicators with 
or without chimes. 

Arising out of Galileo's experiments with Tailing bodies, 
some of which got him into trouble with the religious 
authorities, came gravity-operated apparatus demonstrating 
reproducible time intervals. One example, still in the 
Florentine collection, has a ball running down a groove 
some ten feet long and triggering the hammers of small 
bells en route. This found further expression in a variety of 
clocks, one of which we have mentioned in the introductory 
article. Some reasonably accurate timepieces have been 
made on this basis, but a more or less parallel development 
gained general attention. This was a train of gears powered 
by weights or springs. The date of the latter is uncertain 
but there is a painting in Belgium which shows a timepiece 
which could be spring driven suggesting about 1460. 
However, the early emphasis was on gravity. To slow down 
the rotation of the gears to the speed required vanes were 
used to create air friction, but air is a viscous fluid and the 
result subject to considerable errors with temperature and 
humidity change, apart from the effects of local draughts. 
The idea of arresting the rotation and releasing it at fixed 
time intervals became general and many inventors made a 
contribution. The need for more accurate and convenient 
measurement of time in connexion with the determination 
of longitude for navigational purposes held out promise 
of reward and advances in astronomy were also focusing 
attention on the matter. Galileo was, by this time, blind, 
but this did not stop his flow of ideas. We know from 
Favaro's book, sub-titled "Nuovi Studi Galileana", pub- 
lished in Venice in 1891, that Galileo was in correspondence 
with the Dutch Government, which was probably a 
link with Huygens. Galileo put forward the possibilities 
of the pendulum with a recording device (later proved 
impracticable) to count the oscillations. This, of course, 
goes back to his very early work with the Pulsilogia. He 
also suggested co-operation with Huygens to speed up the 
solution of the problem of determination of longitude. 
Nothing tangible came of this correspondence but Galileo 
pursued the subject. He dictated a sketch to his son— 
Vinccnzio— in 1641, the last but one year of his life. Vin- 
cenzio himself died in 1649 without having completed the 
pendulum and escapement detailed to him. However, 




Fig. 6. Solar and lunar "clock" with hinged alidade 



Viviani made a proper drawing of the scheme, which is 
shown in Fig. 10. The original of this is still preserved in 
Florence. The project then escaped attention for a long 
time, but in 1883 a clock was made in Florence by Porcel- 
lotti employing a spring-driven train of gears with Galileo's 
pendulum and escapement. This beautiful clock, shown in 
Fig. 1 1, was damaged in the 1966 floods, but the mechanism 
was recovered and the case will be remade in due course. 
There has been great debate as to who was the originator 
of a properly functioning pendulum clock. Claims are 
made, among others, by Burgi of Switzerland and Harris 
of London. We know that Galileo arrived at the law of 
isochronism in 1581 and that he detailed a design in 1641 



Fig. 7. Lunar "clock" with visual scale and ratchet scale for 
reading digitally 




20 




Fig. 8. Universal "clock" incorporating an astrolabe 

that was ultimately proved to be practical, which is the 
earliest established date of actual invention. Huygens 
published a learned treatise on the subject — "Horologium" 
— in 1658, and another — "Horologium Oscillatorium" — in 
1673, and he would appear to be responsible for the produc- 
tion of the first successful clock. This used a "verge" 
escapement, considered inferior, so that it is probable that 

Fig. 9. Quadrant, thought to have been made in Naples in 1553 




in spite of the correspondence mentioned, Huygens was 
unaware of Galileo's escapement. Huygens' first clock 
was the work of Salomon da Costa and is in the Museum 
for the History of Science at Leiden. 

Galileo's escapement was of the pinwheel type which did 
not come into extensive use for over a century. The escape 
wheel has twelve teeth which are locked by a hinged detent 
and also twelve projecting pins which engage with an 
impulse pallet carried by the pendulum. The latter also has 
an unlocking pallet which engages with the detent. Near the 
end of the pendulum's swing the detent is released and the 
wheel freed. The wheel moves until one of the pins engages 
with the impulse pallet and the wheel made to recoil. The 
pendulum is impulsed during the next swing until the 
detent falls into the locking position. Interference with the 
pendulum at the end of its swing tends to detract from its 
accuracy. 




Fig. 10. Viviani's drawing of Galileo's pendulum and escapement 

Another difference between Galileo and Huygens' 
design was the length of the arc of the pendulum swing. 
Galileo's had an amplitude between five and six degrees, 
thus keeping the circular error to a minimum. Huygens 
was of a much larger angle and of the type known as 
"cowtail" — intended, as it is, to be descriptive and not 
facetious. A truly isochronous pendulum must swing in a 
cycloidal arc which is a little narrowerthan the corresponding 
arc of a circle. To offset the disadvantage of the larger arc 
and to achieve a true cycloidal pendulum, Huygens intro- 
duced two curved strips of metal near the suspension point 
of the pendulum with which the suspension made contact 
during its swing so as to modify the effective length of the 
suspension as it moved through its arc. This device intro- 
duces more troubles than it cures. 




Fig. II. Clock employing Galileo's ideas made by Porcellotti in 
1883 



While both these two pioneers had made useful contribu- 
tions, the next major step forward was the "dead beat" 
escapement due to Graham of London. This eliminated 
the earlier defects and brought about much more accurate 
time measurement. 

Another debate centred round the wheel escapement of 
which both Huygens and Hooke claimed to be the origina- 
tor. Huygens employed a balance wheel with a spring of 
many turns, acting through a contrate wheel. It made 
several revolutions for each beat. Hooke's arrangement 
provided for partial rotation with a smaller spring, and was 
much closer to the device as it is used today. Whatever 
the relative merits of their claims, it was Hooke's device 
that came into general use. 

While there may be doubts about priority of achievement, 
the extent of communications, and the part played by many 
interested workers, there can be no doubt that the work of 
Galileo, Huygens and Hooke opened up a new era in the 
measurement of time on which Harrison set the seal with 
his Marine Chronometer in 1736. The result of over thirty 
years' work, which may be solace for some of the developers 
of today who may be criticised for taking too much time! 

Following these major events many valuable timepieces 
were modified to use spring, pendulum and escapement. 
One of these is shown in Fig. 12. While they gained in 
mechanical sophistication, convenience in use and the 



ability to measure long or short intervals of time, from a 
zero set by man, they lost their direct link with (but not 
their basic dependence on) that omnific arbiter of time — the 
sun. 

Bibliography 

S. A. Bedini. "Physis" Vol. 5. 1963. 

British Clocks and Clockmakers. K. Ullyclt. Collins. 
London. 

Enciclopedia Mondadori delle Scienze. S4. Fdgardo 
Macorini. Florence. 1968. 

Favaro. Galileo e Suor Maria Celeste. Venice. 1891 

Galileo -His Life and Work. J. J. Fahie. John Murray. 
London. 1903. 

Huygens. Horologium. 1658. HorologiumOscillatorium. 
1673. 

Scientific Instruments in Art and History. H. Michel I. 
Barrie Rockliff. London. 

Note About Galileo's Instruments. Maria L. R. Bonelli. 
The Institute and Museum of the Story of Science. Florence. 
1964. 

A History of Technology. Editor Charles Singer. 
Oxford. 1957. 

Some Outstanding Clocks over Seven Hundred Years 
Old. London. 1958. 

The Marine Chronometer. R. T. Gould. 




Fig. 12. Astronomical clock with miniature armillary sub- 
sequently modified to employ a spring-driven pendulum move- 
ment 



PART 4 MAINLY METEOROLOGICAL 



#p£o\ 



^1 Kl Mo 



This is the fourth of a series of 
articles giving some of the early 
history of instruments, more particu- 
larly, that part of it associated 
with the Galilean School and Its 
work now preserved in the Institute 
and Museum of the Story of Science 
at Florence — the centre from which 
spread the Renaissance. 

Somewhere near the beginning of 
the story there appeared Galileo, 
who adopted as his motto and guid- 
ing principle "Prove and reprove" — 
an ideal supported for a brief but 
brilliant period by the Accademia 
del Cimento, who also accepted 
Galileo's principle and embodied it 
in the frontispiece of their publica- 
tion "Saggi di naturali esperienze" 
which is reproduced as the heading 
illustration linking this series of 
articles. Although the standing joke 
of this age is "listen carefully to 

the weather forecast and then do the opposite" we are far less dependent on the elements than men of earlier tim. 
the early thermometers one has to admire the ingenuity of the early Accademicions and at the same time we should 
somewhat longer expectation of life that this work has brought us. 




is. 



Looking at 
be glad of the 



THERE is little doubt that the first efforts of man to 
understand his surroundings, that led to methodical study, 
were directed at the heavens. The main centres of study 
were the temples and much of the knowledge gained was 
intermingled with religious practices such as siting pyramids, 
dating ritual sacrifices and, later, orientingChristian churches 
to the east or facing the Muslim towards Mecca. All this 
was of little practical value to the ordinary people. As men 
ventured further from shore and experienced the necessity 
for navigation they were forced to take an interest in 
astronomy and some of the knowledge of the temples 
spread to the mariners. It was some centuries later before 
any consistent attempt was made to study atmospheric 
conditions of importance to the mariners and also to the 
tillers of the soil. The simple reason for this being the 
absence of means of assessing the four main factors — 



temperature, atmospheric pressure, humidity and air 
movement. During the Renaissance means of measurement 
began to appear and under the aegis of the Accademia del 
Cimento these means were sufficiently standardized to 
enable observations to be taken by unskilled operators at 
different points over a wide area. The Accademia also 
specified the conditions under which measurements were to 
be made. To this body, and the religious orders that co- 
operated, must be given the credit for setting up the first 
systematic meteorological study. 

The philosopher contemplated, the physicist invented, 
but it was the craftsman that implemented. At Murano, 
near Venice, glass had been melted and blown into decora- 
tive and also utilitarian shapes for, even at that time, 
hundreds of years. They had then, as they have now, a 
remarkably high level of dexterity and manage without, as 



23 



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'^/(•**,L-.ts-M' %*a*?-~ic4l ■ 






9<.\ «*-!>• ' 1 ^*" &«^« »** « »'* ' !i-B 




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$far*J*4U ^l w*6 A> «s»SSCJli»A'< I 






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1 



fi£, /. A page from trie records of the Accademia del Cimento 



the writer saw for himself a year or two back, any instru- 
ments whatever save a pair of calipers. It was from this 
reservoir of skill that the Accademia drew their glass- 
blowers who brought the Florentine thermometers into 
being. 

Figure 1 shows one of the many pages from the records 
of the Accademia dealing with these and is typical of the 
way in which they noted their experiments and the results 
obtained. The top sketch A shows an early form with a 
characteristic mode of graduating the stem — small globules 
of glass fused on. The bottom vessel contained wine, an 
easily available coloured fluid in the vicinity. Warming the 
bulb expanded the air within it so that some escaped. On 
cooling, the wine rose into the stem and gave some sort of 
reading which would, of course, be affected by the initial 
temperature, barometric pressure and have had a very 
considerable time lag. Sketch B, alongside, shows the 
change from expansion of air to expansion of liquid with 
a closed end giving freedom from atmospheric pressure 
effects and making it transportable —very much the glass 
thermometer as we know it today. However, it lacked 
sensitivity and the further developments pursued suggest 
some confusion between length of scale and thermal res- 



ponse. Later models, as Fig. 2, certainly had length of 
scale but the Accademia, with indisputable justification, 
decided that they were too tall and fragile, with the result 
of a further model with an even longer scale but in helical 
form and a considerable reduction in height. This is 
shown in Fig. 3. An instrument man cannot help looking 
at the mass of the bulb and the amount of liquid it contains 
and wondering what its response would be to a step change. 
However, it could and did measure temperature but it 
really represents an interesting exploration leaving the 
work of the new meteorologists to be done with the simpler 
type as Fig. 1 . 

The Accademia arrived at a scale of temperature as 
shown in the "Ccllebrazione della Accademia del Cimento" 
published in 1957. The following comparisons are extracted 
from the full table given therein. 



Accademia 


Reaumur. 


Celsius 


13-5 








22-0 


100 


12-25 


300 


20-0 


25-0 


38-5 


30-0 


37-5 


46-7 


40-0 


55-0 


50-0 


44-0 


55-0 


800 


80-0 


1000 



Returning to Fig. 1 and referring to the middle pair of 
sketches. Hollow glass spheres of adjusted densities arc 
contained in sealed glass phials containing a mixture of 
alcohol and water. The spheres are coloured but that is a 
convenience and not essential to the operation of the 
device. Change of temperature causes the glass spheres to 
change their level. The idea is illustrated in Fig. 4. In one 
model the first sphere rises at 20° the second at 30° and 
so on. This approach was abandoned as they were, in a 
literal translation from the Italian, too lazy. That they 
would have a slow response to temperature change is 
apparent but it would be interesting to know how they 
compared with the instrument in Fig. 3. We must not lose 
sight of the Accademia's urge to measure but it does seem 
that the gravity device might have been developed for use 
where a simple "right or wrong" indication was all that was 
needed. The pair shown at C in Fig. 1 suggests that the 
phial could be masked for ninety per cent of its length, 
provided with one red ball and arranged to give, say, a 
low temperature warning on a domestic water supply. 
The completely non-technical and somewhat short sighted 
could readily appreciate the necessity for action against 
frozen pipes when the red appeared. This gravity type 
was applied to the measurement of fever temperatures. 
The deliberately frog-like "botticina" being strapped to 
the patient and the rise of the different coloured spheres 
noted (Fig. 5). The competitive device, at the time, was 
something similar to the first type mentioned above and 
involved the patient breathing on the bulb. 

The skill of the glassblowers was responsible for another 
piece of apparatus and that was the hydrostatic balance. 
Archimedes' principle had been known for centuries. It 
involved a comparatively complicated procedure but 
Galileo arrived at the idea of a balance which enabled the 
specific gravity of a body or that of a liquid to be determined 
directly and the glassblowers made the idea a practical 
proposition with a piece of apparatus made entirely of 
glass. 

We feel that we cannot leave the subject of glass work 
without a final tribute to their skill and also to that of the 
gracious living of the gentlemen of the Accademia as 
exemplified by the wine glasses used by them and shown in 
Fig. 6. 



24 



Fig. 2. Long stem thermometers 
with fused on graduations 




One of the big debates of the day was the nature of 
vacuum. Arguments between individuals and entire schools 
were rife and sometimes bitter. Lifting pumps were in use 
and those that tried withdrawing a piston from a closed 
ended cylinder were convinced it was a "force". There 
were many theories and many fallacies. Even Galileo 
himself considered the reason why water could not be 
lifted above the height we take as normal was that it broke 
up under its own weight. Some had the impression that 
vacuum was a state of complete "nothingness". Many 
experiments were made and it is not clear whether apparatus 
eventually applied to the measurement of atmospheric 
pressure arose from the vacuum argument or were devel- 
oped to ascertain the weight of the atmosphere. Some of 
the sketches of the time suggest that the mercury column 
was employed to show the partial vacuum obtained by a 
hand-operated suction pump. Others show attempts to 
measure the condition in the space above the mercury 



when employed as a barometer. Out of all the discussion 
and experimentation appeared the apparatus associated 
with the name of Torricelli. In due course the effect of 
altitude on atmospheric pressure was observed and gradual 
changes in it connected with weather conditions. However, 
its use was restricted because the original form of glass 
bowl and inverted tube with mercury did not lend itself 
to portability. However, much of the early meteorology 
was indebted to it. 

About the first instruments that were reasonably trans- 
portable were made by Quare in London. He constructed 
the sump or reservoir for the mercury of leather which 
could be compressed and thus gently force the mercury to 
the top of the column. He also put a restriction in the 
column. These two features prevented the glass column 
being fractured by an internal blow from the mercury 
following a sudden change of angle or level when being 
moved. There is, in the Institute, one of Quare's models 




Fig. 3. Revised form of long stem thermometer 



which is shown in Fig. 7. Another contribution in this 
field was made by Hooke with his well-known syphon 
barometer of which there is a beautiful example in the 
Florentine collection. Hookc's barometer is, of course, 
tapped daily in thousands of homes and has been described 
as the only instrument in which a design defect is an advan- 
tage in use, namely the effect of the backlash in the mech- 
anism on the pointer that makes it apparent whether 
pressure is rising or falling. 

One cannot leave the Florentine collection without 
referring to Felice Fontana who, in the late eighteenth 
century, was responsible for a recording barometer or 
barograph. This is reminiscent of Hooke's arrangement 
but ihe float on the syphon leg, instead of being connected 
to a counterweight running over a pulley, is linked to a 
balanced beam from which extends a stylus. This stylus is 
depressed at intervals by a clock mechanism which gives 
a record in the form of a succession of punctures in the 
paper chart (Fig. 8.). This, so far as the writer has been 
able to ascertain, is the first known example of a recording 
barometer and must be one of the first recorders for any 
purpose. The recording basis, puncturing paper, has been 
reinvented two or three times since then perhaps inde- 
pendent thought but perhaps some designers did their 
history homework. There is no evidence of the manufacture 
of any number of these Fontana instruments and, as has been 
said, the first widely based, systematic meteorological 
observations used simple columns of the Torricellian type. 

The moisture content of the atmosphere had, before the 
days of the Accademia, interested students, among whom 
were I'Aberti and Leonardo da Vinci. Most of them looked 
to absorbent substances, particularly natural sponge, 
weighing before and after exposure to moist air. Leonardo 
sketched a balance in which the absorbent mass is compared 
with a non-absorbent mass of equal zero weight with a 
view to obtaining a continuous indication. The original 
sketch, on vellum, is in the British Museum Most of 
Leonardo's efforts are wonderfully complete in detail 
but this must have been the quickest sketch he ever made 
and consists of four lines However, it conveys his idea 
and working models were subsequently made from it This 
was probably the forerunner of a practical and reasonably 
accurate gravimetric type made by Adams of London, one 
of whose instruments. Fig 9, is in the collection at Florence. 
As can be seen it consists of a pivoted beam, one end of 
which traverses a scale while the other supports about 




Fig. 4. Gravity change 
thermometers 



26 



Fig. 7. A transportable barometer by Quare (left) 

Fig. 8. The first known barograph due to Felice Fontana 




Fig. 6. Wine glasses used by the members of the Accademia del 
Cimento 



27 




Fig. 10. Hygrometer by 
Francesco Folli da Poppi 



fifty discs of paper about lin. in diameter. It is thought 
that these discs may have been impregnated with a salt to 
increase the rate of absorption of moisture from the air 
and also the speed with which it was given up. It has a 
clear and uniform scale and was generally accepted as 
giving a reproducible and continuous indication of humid- 
ity. 

Felice Fontana employed another method not really in 
the absorbent class but still dependent on the measurement 
of weight. He took a piece of glass plate, dried it in hot 
ashes and weighed it. After chilling, it was exposed to 
moist air long enough for condensation to occur when it 
was re-weighed and the amount of water put down ascer- 
tained. 

All these absorbent types suffered from slow response 
and the difficulty of establishing completely dry and 
completely saturated air for calibration purposes. Fontana's 
method for dry conditions was not applicable to the 
absorbents owing to their ability to entrain some of the 
ash. Even today it is not possible to guarantee complete 
dryness although we can get much closer to it than the 
Renaissance pioneers. Similarly there is still difficulty 
at the other end of the scale— anything over 95% must be 
suspect because of the effects of dew deposition. This 
observation, of course, also applies to the other types that 
follow. This disadvantage was later sidestepped by the 
wet and dry bulb thermometer method which substitutes 
temperature calibration for humidity comparison. 

One of the earliest satisfactory instruments to measure 
humidity was constructed by Santoro Santori ( 1 56 1 to 1 6 1 1 ). 
It employed a cord stretched between two fixed points with 
a weight at the centre which acted as an index moving over 
a vertical scale. This approach was followed by many 
others, some of whom introduced a pulley with a view to 
magnifying the change in length of the cord or transferring 
the motion to a pointer on a dial. Perhaps the most interest- 
ing of these is due to Francesco Folli da Poppi of Casen- 
tino, shown in Fig. 10. In this example the cord is still held 
at both ends and a link to a pulley is taken from the centre. 
The pulley carries a pointer traversing a circular scale. 
Transfer the cord and link to the pulley to a vertical posi- 
tion, substitute human hair, goldbeaters skin or silk for 
the woven cord and you have the type of simple hygro- 
meter widely used today — some three hundred years later. 

Instruments to measure humidity were much more 
utilitarian than many of the earlier instruments for other 
purposes and consequently lacked the decoration that had 
!"een characteristic. An exception is the famous condensa- 
tion apparatus produced for the Accademia and still 
preserved in Florence, Fig. II. It comprises a cork-lined 
cone which was filled with crushed ice which chilled a glass 
extension. An overflow ensured that the melting ice was 
free from water and that this water was kept separate. 
Moisture from the air condensed on the glass extension and 




Fig. II. The atmospheric condensation apparatus made for the 
Accademia del Cimento 



28 







Fig. 12. An early windvane 
with thirty-two point windrose 



dripped into a collecting vessel suitable for measurement. 
There were various means of arriving at the uniform timing 
required but somehow the sandglass seems appropriate. 
The fourth requirement for the meteorology of the 
Accadcmia was the wind direction and the wind force. One 
suspects that many of the observations were based on 
smoking chimneys but the compass card was already 
recognized as having 32 points, four of which went to a 
"wind", so some more accurate means was desirable for 
research purposes. Fig. 12 shows one example. The wind 



direction positioned the vane which is linked via pinwheel 
gears to the pointer. The dial shows the principal four 
quarters each divided into eight. The materials of con- 
struction and the nature of the surface finish suggest that 
it was not intended to be left in the open air during all 
weathers. It was associated with an anemometer consisting 
of a rectangular plate carried on a graduated bar traversing 
a hollow handle. When the plate was presented to the wind 
the bar would be forced back into the handle and against 
a spring. The graduations could be counted and a 
reproducible reading obtained but the calibration must have 
been arbitrary. 

These two instruments suggest that they were kept 
indoors and only taken out when readings were required. 
It must have been an unpleasant procedure when the 
observations would be of great interest during rain and a 
howling gale on a dark night. However, the meteorological 
system was operated by religious orders so perhaps these 
observations came under the heading of "penance". 



Biblioteca Nationale di 



Bibliography 

Saggi di naturali csperienzc. 
Firenza. 1666-1667. 

Celebrazione della Accademia del Cimento. nel Tricen- 
tenario dclla Fondazione. Presso la Domus Galileana. 
Pisa. 1957. 

Un esperienza di Vincenzio Viviani. Fatta dalla torrc 
di Pisa. Dr. M. L. R. Bonclli. "Physis" Vol. 1. Fasc 1. 
1959. 

A History of Technology. Editor — Charles Singer. 
Oxford. 1957. 

Scientific Instruments in Art and History. 
Barrie Rockcliff. London. 

A History of Pressure Measurement. L. B. 
Transactions of the Society of Instrument 
1963. 

A History of Humidity Measurement. L. B. Lambert. 
Instrument Practice. 1965. 

Enciclopcdia Mondadori delle Scienzc. S4. 
Macorini. Florence. 1968. 



H. Michell. 

Lambert. 
Technology. 



Fdgardo 



Museo Di Storia Della Scienza 

Information for Visitors to the Museum in Florence 



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Wagons/Lits via Tornabuoni, Firenza. 

Istituto Tccnico Galileo Galilei, via 
Giusti, Firenza. 



29 



PART 5 MAINLY OPTICS, MAGNETICS AND STATICS 




This is the last of a series of articles 
giving some of the early history of 
instruments, more particularly that 
part of it associated with the 
Galilean School and its work now 
preserved in the Institute and 
Museum of the Story of Science at 
Florence — the centre from which 
spread the Renaissance. 

Somewhere near the beginning of 
the story there appeared Galileo, 
who adopted as his motto and guid- 
ing principle "Prove and reprove" — 
an ideal supported for a brief but 
brilliant period by the Accademia 
del Cimento, who also accepted 
Galileo's principle and embodied it 
in the frontispiece of their publica- 
tion "Saggi di naturali esperienze" 
which is reproduced as the heading 
illustration linking this series of 
articles. The instrument making 
industry can trace its first "mass 

production" efforts back to the grinding machines for lens work when the demand outstripped the earlier "one off" system, 
period was when observation replaced magic and machines were used to supplement exquisite workmanship. 



This 



IN THE YEAR 1610 some unsuspected features of our 
constellation were seen for the first time. Galileo had 
completed his astronomical telescope and had seen that 
the Moon did not have the smooth surface as generally 
believed but was pitted, ridged and lined. He also saw 
that Jupiter had four satellites and that Saturn had a 
different feature — its rings. All this was recorded and 
published in twenty-four highly significant pages of the 
"Sidereus nuntius" which contradicted much of the philo- 
sophical thought and religious beliefs of the time. The 
possibility of other planetary systems with their own earth, 
associated moons and stars with, possibly, other civilisa- 
tions was too startling to be reconciled with many ideas 
of which man had talked with so much confidence and for 
so long. It brought trouble from the Inquisition but it 
also brought a great deal of genuine interest from scientists 
in many countries. These first views of the Moon were as 



big a step forward as the explorations of today but the 
impact must have been far greater — we are inured to 
scientific progress and the spectacular presentation of it. 
The first authenticated reference to the telescope or 
microscope was an idea for improved or enlarged sight in 
a communication from Giovani Faber to the Prince 
Federico Cesi, founder of the Accademia dei Lincei. 
While Galileo did not invent the lens he saw its possibilities 
and made rapid strides in the development of simple and 
compound types that made his astronomical work possible. 
His original ocular is shown in Fig. 1. This is an unusual 
view as the ocular was mounted in an ivory plaque in 
1677 by Vittorio Croster and this assembly provides the 
illustration normally used. The plaque, together with 
two of Galileo's telescopes can be seen in the Institute at 
Florence. The latter are shown in Fig. 2. The first has a 
tube made of wood and covered with paper. It is 1 -36m 



30 




fig. I. Galileo's ocular — made in 1610 



Fig. 2. Two of Galileo's telescopes 




long, has an effective aperture of 26mm and a focal length 
of l-36m with a planoconcave lens and gives a magnifica- 
tion of fourteen times. The second is formed of a tube of 
wood covered with leather and embossed in gold. It is 
0-92m long, has an elfcctive aperture of 16mm, with a focal 
length of l-96m and an objective consisting of a biconvex 
lens with a magnification of 20 times. We are told that the 
construction of the tube presented more difficulty than 
that of" the lenses. There was not, at the time, any means of 
drawing tubes or swaging it to closer dimensions or to a 
taper. Many of them were made of paper or parchment 
wound on to mandrels and stiffened with lacquer. Whether 
made in wood or paper it was dilficult to get them con- 
centric to start with and keep them so with changes of 
humidity. Two of Galileo's telescopes were mounted side 
by side in an outer support of rectangular section which 
also suffered from the same lack of suitable materials and 
must have presented considerable difficulty in optical 
alignment. Its weight and dimensions made a tripod 
essential but it seems to have worked and can be regarded 
as the forerunner of the binocular. 

Galileo's lenses were made by hand but the demand that 
he had accelerated brought in various machines — one of 
which appeared about a hundred years later and is shown 
in Fig. 3. The urge for embellishment had not entirely 
gone and its excellent condition suggests that it was either 
used with drawing room care or not used much at all. 

Another constructional difficulty that had to be over- 
come before much progress could be made with focusing 
arrangements as well as the machine aids to manufacture 
was the production of better screw threads. Hero's method 
of cutting a triangle in flexible sheet and winding it round 
a rod so that the hypotenuse could be used to mark off 
the pitch of the thread was slow and not very precise. 
Leonardo da Vinci sketched a machine which was developed 
by others and which we show in Fig. 4. Turning the handle 
rotates two lead screws which advance the block carrying 
the cutter that planes off the screw blank and, in a number 
of traverses, produces a thread. Change wheels enable 
different pitches of thread to be obtained from the same 
lead screws while the bearing blocks can be moved for 
different diameters of screws. This device reverses the 
direction of thread between the lead screws and the pro- 
duced thread whereas Leonardo's sketch shows all three 
to be left-handed. From this error it is argued that he did 
invent the machine and was not copying something he could 
see or his artists' eye for detail would have operated against 
this mistake. 

Galileo's lead was taken up by, amongst others, Giuseppe 
Campani and Eustachio Divini of Rome but the school at 
Florence continued to be very active in this field and both 
telescopes and microscopes improved fairly rapidly. 
Figure 7 shows two microscopes that have been attributed 
to Galileo but there is no proof of this and it is probable 
that they are the work of Campani or Divini. Figure 5 
shows a line drawing of three microscopes from the records 
of the Accademia del Cimento which reinforces the view 
that the metal bodied ones were of later date. 

Illumination of the specimen to be studied was another 
problem. Mirrors were introduced fairly quickly that were 
helpful for light porous matter but completely opaque 
specimens demanding adequate top light needed different 
treatment. Some of these were a sort of periscope that 
could bring sunlight to bear from awkward angles but 
one arrangement is of particular interest. This is a micro- 
scope due to Filippo Pacine which employed a prism 
combination to enable the microscope objective to be 
underneath the platform looking upwards and leaving the 



31 



space above the specimen freely accessible for lighting 
or for manipulation of the specimen. 

We have commented on the first significant things seen 
by telescope. There is no similar clearly defined parallel 
in the case of the microscope but there is some evidence 
of the microscopical examination of insects, including 
some of those too small to be seen by the unaided human 
eye. Not having the advantage of photography the observer 
had to be something of an artist or to enlist the services 
of one. An example of the result is shown in Fig. 7 and is 
the cheese mite as seen in 1687. 

It is indeed fortunate that the ocular of Galileo, his 
telescopes and the early microscopes escaped damage 
during the Arno floods to which we referred in an earlier 
article. 

We have already touched on two machines intended to 
facilitate the production of instruments. A third was the 
instrument developed by the Duke Chaulncs (1714 to 1769) 
who worked in France. This optical device was employed 
to measure the refractive index of glass and did much to 
assist the production of better and more consistent glass 
and, hence, better lenses (Fig. 8). 

Another piece of progressive apparatus was the dividing 
machine. This not only assisted the preparation of tympani 
for astrolabes and dials for other types of instruments but 
also aided the production of gears of greater precision which, 
in turn, led to improved screw threads. This had a con- 
siderable impact on instruments, especially the microscope, 
where the means of adjusting the focus had lagged behind 
the ability of the lenses of the time. 

The improvement in gears and threads also brought 
better machine tools. All this contributed to the establish- 
ment of instruments as an industry, small but recognizable 
as such. In the first half of the seventeenth century scientific 
apparatus was entirely hand made and usually on a "one 
off" basis to further the studies of one man. Galileo's 
discoveries played a big part in stimulating interest. His 
success with the telescope created a demand for lenses from 
all over Europe and signalled the birth of the optical instru- 
ment as a commercial entity. A few years after Galileo's 
initial work single and compound lenses were being pro- 
duced in some quantity by Leeuwenhoek in Holland. The 
invention and production of machines became as important 
as the development of the instruments themselves. Ob- 
viously one helped the other and progress, at first slow, 
quickened and by the end of the century some parts of 
instruments had definitely moved from the "one off" 
basis to batch production and thence, during the next 
century, to the batch production of complete instruments, 
even if only in small numbers. 

We must now go back in time once again and follow up 
another part of the instrument story — that relating to 
magnetism and static electricity. The phenomenon of 
magnetism, as evidenced by the loadstone, was known to a 
very limited extent, in antiquity. Its first use seems to have 
been as a mechanism to extract goods or cash from the 
unwary. An apparently innocent object, such as a wooden 
fish, containing some magnetic material and floating in a 
bowl of water could be guided to "yes" or "no" signs or, 
alternatively, to letters to make up a name or give an 
answer to a posed question, by a loadstone secretly moved 
by the operator. A name so. apparently, chosen by the Gods 
was expected to give the recipient a good start in life and 
worth a good fee. It was but a short step from this device 
to the early compass in which a shaped piece of loadstone 
would be incorporated in the float which was left free to 
indicate the North. As it led to the North it became known 
to mariners as the "leading stone" and thence to "load- 




Fig. 3. An early lens forming and polishing machine 



Fig. 4. Thread cutting machine as sketched by Leonardo da 
Vinci 



«:g| 




......V-rr-r- *r •V 1- *': 




32 



stone". There is some evidence that it was known in China 
but later research suggests that it was the Scandinavians, 
the earliest long distance navigators, who developed the 
early form of compass and put it to practical use. It 
appears that the Scandinavian experience with the load- 
stone was communicated to the Normans, who had estab- 
lished a colony at Amalfi now well known as an Italian 
holiday resort. It was from this colony that the early 
knowledge spread throughout the Mediterranean area 
including, of course, the rest of Italy. 

One of the earliest records of any scientific approach to 
the subject of magnetism is that by Robert Norman, of 
Wapping, who published his work "Newe Attractive" in 









Fig. 5. Drawing of three early microscopes reproduced from the 
records of the Accademia del Cimento 



1581. It is possible that he was anticipated by Gerolamo 
Cardano about thirty years earlier but there is no clear 
record of this. However, the first real understanding can 
be seen in William Gilbert's famous treatise "The Magnet" 
which appeared in 1600. In this he made clear the difference 
between magnetic attraction and electrostatic attraction 
and established both as seperate natural forces and divorced 
them from the atmosphere of "magic" that had previously 
surrounded them. The subject did not escape Galileo's 
attention and his work was carried on by the Accademia del 
Cimento. The illustration, Fig. 9, shows apparatus, 
preserved in the Florentine collection, devised by Galileo. 
This demonstrates the force exerted by loadstones and was 




Fig. 6. A model of the thread cutting machine as sketched by 
Leonardo da Vinci. "Crown copyright. Science Museum, London". 

most probably used to show the useful effect of arming the 
natural stone with soft iron poles so as to concentrate 
the magnetic force. The lifting power of the magnet could 
be evaluated by varying the weights in the decorative box, 
the whole being raised by the magnet. From the records 
of the Accademia del Cimento we reproduce a sketch 
showing an experiment in attraction and repulsion of a 
magnetized needle by other magnets (Fig. 10). 

In these early days the principal use of their knowledge 
was the magnetic compass which received a considerable 
fillip when it proved possible to dispense with floating 
devices and make it liquid free, compact and readily 
portable. For a time the method of magnetizing a needle 
and pivoting it was a closely guarded secret of commercial 
value but with so many workers in so many countries it 
cannot have remained so for very long. Brass cases were 
quite common and the needle and scale were protected 
by mica but this was soon replaced by glass. The compass 
could now be made small enough to be embodied in 
many other instruments, some of which have been described 
in earlier articles. One of the popular uses was intended 
for the traveller. The compass was mounted together with 
a gnomon on a base carrying sunlines. The gnomon was 
often hinged so that it could be folded down. Between 
the base and the gnomon would be a thread. The compass 
was used for directional purposes and also to orientate 

Fig. 7. Two early microscopes — possibly the first to have thread 
focusing 




33 



the device to the North when the shadow of the thread 
would fall on the sunlines and show the time. A number of 
these have survived. Most are attractively decorated and 
some are made in precious metals. All are valued museum 
pieces. 

The fact that a free-moving magnetized needle pointed 
to the North was appreciated centuries before it was realized 
that it dipped from the horizontal an increasing amount as 
it was carried towards the Poles. The appreciation that this 
was associated with the earths magnetic field led to the 
shaping of loadstones into "terrellae" or "little Earths" 
which enabled the effect to be demonstrated on a miniature 
scale and attempts were made to use it as a navigational 
aid. The variations in the Earth's magnetic lines were 
discovered and also the deviation from true North (Fig. 1 1). 
Some of the early compasses bore corrections for the devia- 
tion, effected by small pieces of loadstone appropriately 
positioned under the compass card, but these were more 
of the nature of intelligent guesses than established fact. 

Parallel to the growing awareness of the properties of 
the loadstone was the somewhat similar property of amber. 



\^U 













Fig. 7. One of the early forms of life to be seen by the micro- 
scope, the cheese mite 



True it had to be rubbed to develop the static charge 
necessary to enable it to attract small pieces of non-conduct- 
ing material and it was not so powerful. In the limited 
demonstration of the time there must have seemed a 
connexion between the two. However, as we have said, 
Gilbert established that they were two distinct forces and 
the scientists of the Renaissance treated them as such. 
There were few known substances in Nature that lent 
themselves to the controlled generation of static electricity 
and amber was almost as rare as loadstone. Later sulphur 
came into the picture and was used by Otto von Guericke 
in the first rudimentary machine to produce an electric 
spark or an attractive force. Other machines employed one 
of man's earliest synthetics — glass. In each case a sphere or 
cvlinder was rotated by hand via a speed increasing belt 
drive and friction set up by contact with a leather or fabric 
pad — the resulting static charge being collected by metallic 
electrodes. This simple apparatus facilitated a great deal 
of research, especially between 1730 and 1740, leading to 
the first electrical instrument — the Electroscope. The way 

Fig, 9. Galileo's apparatus to demonstrate the power of load- 
stones 




Fig. 8. A major step forward in optical construction — a refracto- 



meter 




34 



Fig. LIU 



'- - '|5.-y-. 




Fig. 10. Early experiments with magnets — reproduced from the 
records of the Accademia del Cimento 



The Renaissance, absorbing Galileo's lead, saw the 
change from intellectual speculative discussion to practical 
demonstration. What was also important was that the 
principle of "Prove and Reprove" was accompanied by 
adequate recording so that knowledge was not lost and 
could be made available to others. Some examples of this 
systematic recording are included in the Museum and 
excite admiration for the excellence of the freehand draw- 
ings, maps and decorative binding, all of which reflect the 
care with which the subject matter was committed to paper. 
It is, of course, only part of that held in the Archives of 
Florence containing, as they do, so much that was new 
and basic in the knowledge of man. 

One cannot help wondering how much more progress 
would have been made by the Galilean School if Galileo 
himself had not been subjected to so much religious persecu- 
tion and had been given proper support. Perhaps he 
sharpened his wits in argument with the Inquisition, perhaps 
a certain amount of austerity kept his brain clear, perhaps 
an easier supply of material comforts would have led to 
overgood living and some stultification. However, it would 
seem that the man's great thirst for knowledge would not 
have been adversely affected and that happier circumstances 
would have provided even more stimulus and an even 
greater contribution to man's development. 

Similarly, one wonders to what extent progress was 
slowed down by the disbanding of the Accademia del 
Cimento. True the anonymity provided by co-operative 
effort was no longer so necessary for the protection of the 
individual but they had accomplished so much and it 
seems a pity that they did not continue. We must, of 
course, be grateful for what they did do towards the con- 
solidation of experimental science. 

The Institute and Museum of the Story of Science docs 
not compare in size with, say, our Science Museum but it 
is an intimate link with the Renaissance and the Galilean 
School, having a pleasant atmosphere all its own. It should 
be visited by anyone interested in instruments who appre- 
ciates artistry and craftsmanship and is prepared to make 
a gesture of gratitude to the era in which our great industry 
really started life. 



was opened for the work of Stephen Gray, Charles du Fay 
and, later, Coulomb, Poisson and Oersted. The latter 
showed the similarity of the field of a magnet and that of 
a conductor carrying an electric current, thus arriving at 
elcctromagnetism. To all this must be added the work of 
Ampere and Volta. The latter wrote to Sir Joseph Banks — 
then President of the Royal Society- describing his experi- 
ments and, in particular, what came to be known as Volta's 
Pile. Thus the original "magic" had become an established 
part of science and the foundation laid for the production 
of the vast array of engineering equipment and the enor- 
mous variety of scientific instruments that we have today. 
A variety that touches all aspects of life and reaches down 
towards the centre of the Earth as well as out to the great 
spaces of the Universe. 

There are some good examples of early electrical appara- 
tus in the Institute at Florence in spite of some losses 
during the Arno floods. The smaller items were either lost 
entirely or severely damaged. Heavier specimens withstood 
the initial rush of water and the subsequent eddies and 
needed little more than cleaning and a coat of varnish. 
They include, besides those already mentioned, electro- 
static and electromagnetic apparatus and an early telephone. 
(Fig. 12), (Fig. 13). 




Fig. II. An instrument to measure magnetic "dip" 



35 




Fig. 12. Galvanometer devised by Leopoldo Nob///' (1787-1835) 
having a stationary coil with a suspended moving magnet 



Bibliography 

Saggi di naturali cspericnze. Biblioteca Nationale di 
Firenze. 1666-1676. 

Celcbrazionc della Accademia del Cimcnto. nel Tricen- 
tenario della Fondazione. Presso la Domus Galilcana. 
Pisa. 1957. 

A History of Technology. Editor — Charles Singer. 
Oxford. 1957. 

Newe Attractive. Robert Norman. 1581. 

The Magnet. William Gilbert. 1600. 

Galileo— His Life and Work. J. J. Fahie. John Murray. 
London. 1903. 

Sidercus Nuntius. Galileo. 1610. 

Scientific Instruments in Art and History. H. Michel I. 
Barrie KocklifT. London. 

Enciclopedia Mondadori delle Scienze. S4. Fdgardo 
Macorini. Florence. 1968. 



Why Look Back? 

'"Wo learn from history that wc do not learn from history". I am sure 
that this is a quotation but it has been with me for so many years that 
I have lost all recollection of the origin. However, the phrase has often 
prompted the question — Do wc learn as much as wc should from the 
past? Wars, politics, and other eruptions of human nature suggest 
that we do not always perceive the lesson that could be learnt or, if wc 
do, we cannot bring ourselves to that point of action which would 
enable us to fully prolit from it. With this query so much in mind 
and for so long it is not surprising that I have an interest in History and 
its use. Alongside this, being essentially a practical type, there has, 
from boyhood, been great interest for me in the skill of human hands. 
I still remember watching an old fashioned french polisher working 
his way through the preliminary sticky stage, the "spiriting off" to 
the final production of a mirror surface. Also watching the local 
watch repairer who repaid my interest with some gratuitous instruc- 
tion. Later in life I have been the audience appreciating the skill of 
ivory carvers in India, the making of wood figures with the crudest of 
tools in Africa, Aborigine techniques in Australia, the delicacy of 
touch used by the moulders of figurines in Denmark, the manipulation 
of hoi glass by the blowers in Murano and so on. The combination of 
interest in the potential lessons of History, great appreciation of 
manual dexterity and my long association with the Instrument In- 
dustry arc. of course, the reasons for my interest in the history of early 
instruments. Over the years I have watched the growth of design 
complication facilitated by a wealth of exciting new materials and 
manufacturing processes all of which necessitates a complex team and 
diminishes the part played by the individual. Wc have lost the personal 
touch and much of the sense of individual responsibility that once 
provided such a spur to progress and a great sense of accomplishment. 
Our pioneers progressed in spite of the limitations of the materials 
and tools available to them and succeeded in laying the foundation 
on which wc have built and I, for one, look back with gratitude. 




Fig. 13. The most modern piece of 
apparatus in the Institute — 
a phonograph constructed 
by Thomas Alva Edison 



36 



HIIKALD I'RINTIKS. Mlltk 



I