= ee mo Sos Pan Ske. erie ce EE Tg TES BELL STI FE Bn Cae oe pw 4 fe COE EEE COC EE Cl EE rege ’ ns Ci C Tak CCE _§ UCC. Gee re ens ae NS ZA Fia. 3.—a represents coil No. 1, 6 helix No. 1, and c, d, handles for receiv- ing the shock. were joined by the magnetizing spiral (11), the enclosed needle became strongly magnetic. Also when the secondary current was passed through the wires of the iron horseshoe (12), magnetism was developed; and when the ends of the second coil were attached to a small decomposing apparatus, of the kind which accompanies the magneto-electrical ma- chine, a stream of gas was given off at each pole. The shock however from this coil is very feeble, and can scarcely be felt above the fingers. 30. This current has therefore the properties of one of moderate “intensity,” but considerable “quantity.” 31. Coil No. 1 remaining as before, a longer coil, formed by uniting Nos. 3, 4, and 5, was substituted for No.2. With this arrangement, the spark produced when the ends were rubbed together, was not as brilliant as before; the magnet- izing power was much less; decomposition was nearly the same, but the shocks were more powerful, or in other words the “intensity” of the induced current was increased by an increase of the length of the coil, while the “quantity” was apparently decreased. 32. A compound helix, formed by uniting Nos. 1 and 2, and therefore containing two thousand six hundred and fifty yards of wire, was next placed on coil No.1. The weight of this helix happened to be precisely the same as that of coil No. 2, and hence the different effects of the same quantity of metal in the two forms of a long and short conductor, could becompared. With thisarrangement the magnetizing effects, 116 WRITINGS OF JOSEPH HENRY. [1838 with the apparatus before mentioned, disappeared. The sparks were much smaller, and also the decomposition less, than with the short coil; but the shock was almost too intense to be received with impunity, except through the fingers of one hand. A circuit of fifty-six of the students of the senior class, received it at once from a single rupture of the battery current, as if from the discharge of a Leyden jar weakly charged. The secondary current in this case was one of small quantity, but of great intensity. 30. The following experiment is important in establishing the fact of a limit to the increase of the intensity of the shock, as well as the power of decomposition, with a wire of a given diameter. Helix No. 5, which consists of wire only z}zth - of an inch in diameter, was placed on coil No. 2, and its length increased to about seven hundred yards. With this extent of wire, neither decomposition nor magnetism could be obtained, but shocks were given of a peculiarly pungent nature; they did not however produce much muscular action. The wire of the helix was further increased to about fifteen hundred yards; the shock was now found to be scarcely per- ceptible in the fingers. , 34. As a counterpart to the last experiment, coil No. 1 was formed into a ring of sufficient internal diameter to admit the great spool of wire (11), and with the whole length of this (which, as has before been stated, is five miles) the shock was found so intense as to be felt at the shoulder, when passed only through the forefinger and thumb. Sparks and decomposition were also produced, and needles rendered mag- netic. The wire of this spool is 7gth of an inch thick, and we therefore see from this experiment, that by increasing the diameter of the wire, its length may also be much in- creased, with an increased effect. 35. The fact (33) that the induced current is diminished by a further increase of the wire, after a certain length has been attained, is important in the construction of the mag- neto-electrical machine, since the same effect is produced in the induction of magnetism. Dr. Goddard of Philadelphia, to whom I am indebted for coil No. 5, found that when its 1838] © WRITINGS OF JOSEPH HENRY. 117 whole length was wound on the iron of a temporary magnet, no shocks could be obtained. The wire of the machine may therefore be of such a length, relative to its diameter, as to produce shocks, but no decomposition; and if the length be still further increased, the power of giving shocks may also become neutralized. 36. The inductive action of coil No.1, in the foregoing experiments, is precisely the same as that of a temporary magnet in the case of the magneto-electrical machine. A short thick wire around the armature gives brilliant defla- grations, but a long one produces shocks. This fact, I be- lieve, was first discovered by my friend Mr. Saxton, and afterwards investigated by Sturgeon and Lenz. 37. We might, at first sight, conclude, from the perfect similarity of these effects, that the currents which, according to the theory of Ampere, exist in the magnet, are like those in the short coil, of great quantity and feeble intensity; but succeeding experiments will show that this is not necessarily the case. 388. All the experiments given in this section have thus far been made with a battery of a single element. This condi- tion was now changed, and a Cruickshanks trough of sixty pairs substituted. When the current from this was passed through the ribbon coil No.1, no indication, or a very feeble one, was given of a secondary current in any of the coils or helices, arranged as in the preceding experiments. The length of the coil, in this case, was not commensurate with the intensity of the current from the battery. But when the long helix, No. 1, was placed instead of coil No. 1, a powerful inductive action was produced on each of the articles, as before. 39. First, helices No. 2 and 3 were united into one, and placed within helix No. 1, which still conducted the battery current. With this disposition a secondary current was pro- duced, which gave intense shocks but feeble decomposition, and no magnetism in the soft iron horseshoe. It was there- fore one of intensity, and was induced by a battery current also of intensity. 118 WRITINGS OF JOSEPH HENRY. [1838 40. Instead of the helix used in the last experiment for receiving the induction, one of the coils (No. 3) was now placed on helix No. 1, the battery remaining as before. With this arrangement the induced current gave no shocks, but it magnetized the small horseshoe; and when the ends of the coil were rubbed together, produced bright sparks. It had therefore the properties of a current of quantity; and it was produced by the induction of a current, from a battery, of intensity. 41. This experiment was considered of so much impor- tance, that it was varied and repeated many times, but always with the same result; it therefore establishes the fact that an “intensity” current can induce one of “quantity,” and, by the preceding experiments, the converse has also been shown, that a “quantity” current can induce one of “intensity.” 42. This fact appears to have an important bearing on the law of the inductive action, and would seem to favor the supposition that the lower coil, in the two experiments with the long and short secondary conductors, exerted the same amount of inductive force, and that in one case this was expended (to use the language of theory) in giving a great velocity to a small quantity of the fluid, and in the other in producing a slower motion in a larger current; but in the two cases, were it not for the increased resistance to conduc- tion in the longer wire, the quantity multiplied by the square of the velocity would be the same. This however is as yet a hypothesis, but it enables us to conceive how in- tensity and quantity may both be produced from the same induction. 43. From some of the foregoing experiments we may con- clude, that the quantity of electricity in motion in the helix is really less than in the coil, of the same weight of metal; but this may possibly be owing simply to the greater resist- ance offered by the longer wire. It would also appear, if the above reasoning be correct, that to produce the most energetic physiological effects, only a small quantity of elec- tricity, moving with great velocity, is necessary. 44, In this and the preceding section, I have attempted 1838] | WRITINGS OF JOSEPH HENRY. 119 to give only the general conditions which influence the gal- vanic induction. To establish the law would require a great number of more refined experiments, and the consideration of several circumstances which would affect the results, such as the conduction of the wires, the constant state of the bat- tery, the method of breaking the circuit with perfect regu- larity, and also more perfect means than we now possess of measuring the amount of the inductive action; all these circumstanees render the problem very complex. SECTION III. On the Induction of Secondary Currents at a distance. 45. In the experiments given in the two preceding Sections, the conductor which received the induction, was separated from that which transmitted the primary current by the thickness only of a pane of glass; but the action from this arrangement was so energetic, that I was naturally led to try the effect at a greater distance. 46. For this purpose coil No. 1 was formed into a ring of about two feet in diameter, and helix No. 4 placed as is shown Fic. 4.—a represents helix No. 4, } coil No. 1, in the form of a ring. in the figure. When the helix was at the distance of about sixteen inches from the middle of the plane of the ring, shocks could be perceived through the tongue, and these rapidly increased in intensity as the helix was lowered, and when it reached the plane of the ring they were quite severe. The effect however was still greater, when the helix was 120 WRITINGS OF JOSEPH HENRY. [1838 moved from the centre to the inner circumference, as at c: but when it was placed without the ring, in contact with the outer circumference, at b, the shocks were very slight; and when placed within, but its axis at right angles to that of the ring, not the least effect could be observed. 47. With a little reflection, it will be evident that this arrangement is not the most favorable for exhibiting the induction at a distance, since the side of the ring, for ex- ample, at c, tends to produce a current revolving in one direction in the near side of the helix, and another in an opposite direction in the farther side. The resulting effect is therefore only the difference of the two, and in the position as shown in the figure; this difference must be very small, since the opposite sides of the helix are approximately at the same distance from c. But the difference of action on the two sides constantly increases as the helix is brought near the side of the ring, and becomes a maximum when the two are in the position of internal contact. A helix of larger diameter would therefore produce a greater effect. 48. Coil No. 1 remaining as before, helix No. 1, which is nine inches in diameter, was substituted for the small helix of the last experiment, and with this the effect at a distance was much increased. When coil No. 2 was added to coil No. 1, and the currents from two small batteries sent through these, shocks were distinctly perceptible through the tongue, when the distance of the planes of the coils and the three helices, united as one, was increased to thirty-six inches. 49. The action at a distance was still further increased by coiling the long wire of the large spool into the form of a ring of four feet in diameter, and placing parallel to this another ring, formed of the four ribbons of coils No. 1, 2, 3, and 4. When a current from a single battery of thirty-five feet of zinc surface was passed through the ribbon conductor, shocks through the tongue were felt when the rings were separated to the distance of four feet. As the conductors were approximated, the shocks became more and more severe; and when at the distance of twelve inches, they could not be taken through the body. 1838]. WRITINGS OF JOSEPH HENRY. 121 50. It may be stated in this connection, that the galvanic induction of magnetism in soft iron, in reference to distance, is also surprisingly great. A cylinder of soft iron, two inches in diameter and one foot long, placed in the centre of the ring of copper ribbon, with the battery above mentioned, becomes strongly magnetic. 51. I may perhaps be excused for mentioning in this com- munication that the induction at a distance affords the means of exhibiting some of the most astonishing experiments, in the line of physique amusante, to be found perhaps in the whole course of science. I will mention one which is some- what connected with the experiments to be described in the next section, and which exhibits the action in a striking manner. This consists in causing the induction to take place through the partition wall of two rooms. For this purpose coil No. 1 is suspended against the wall in one room, while a person in the adjoining one receives the shock, by grasping the handles of the helix, and approaching it to the spot opposite to which the coil is suspended. The effect is as if by magic, without a visible cause. It is best produced through a door, or thin wooden partition. 52. The action ata distance affords a simple method of graduating the intensity of the shock in the case of its appli- cation to medical purposes. The helix may be suspended by a string passing over a pulley, and then gradually low- ered down towards the plane of the coil, until the shocks are of the required intensity. At the request of a medical friend, I have lately administered the induced current precisely in this way, in a case of paralysis of a part of the nerves of the face. 53. I may also mention that the energetic action of the spiral conductors enables us to imitate, in a very striking manner the inductive operation of the magneto-electrical machine, by means of an uninterrupted galvanic current. For this purpose it is only necessary to arrange two coils to represent the two poles of a horseshoe magnet, and to cause two helices to revolve past them in a parallel plane. While a constant current is passing through each coil, in opposite 122 WRITINGS OF JOSEPH HENRY. [1838 directions, the effect of the rotation of the helices is precisely the same as that of the revolving armature in the machine. 54. A remarkable fact should here be noted in reference to helix No. 4, which is connected with a subsequent part of the investigation. This helix is formed of copper wire, the spires of which are insulated by a coating of cement in- stead of thread, asin the case of the others. After being used in the above experiments, a small discharge from a Leyden jar was passed through it, and on applying it again to the coil, I was much surprised to find that scarcely any signs of a secondary current could be obtained. 55. The discharge had destroyed the insulation in some part, but this was not sufficient to prevent the magnetizing of a bar of iron introduced into the opening at the centre. The effect appeared to be confined to the inductive action. The same accident had before happened to another coil of nearly the same kind. It was therefore noted as one of some importance. An explanation was afterwards found in a peculiar action of the secondary current. SECTION IV. On the Effects produced by interposing different Substances be- tween the Conductors. 56. Sir H. Davy found, in magnetizing needles by an electrical discharge, that the effect took place through in- terposed plates of all substances, conductors and non-con- ductors.* The experiment which I have given in para- graph 51 would appear to indicate that the inductive action which produces the secondary current might also follow the same law. 57. To test this the compound helix was placed about five inches above coil No.1, Fig. 5, and a plate of sheet iron, about =jth of an inch thick, interposed. With this arrange- ment no shocks could be obtained; although, when the plate was withdrawn, they were very intense. 58. It was at first thought that this effect might be pe- * Philosophical Transactions, 1821. 1838] WRITINGS OF JOSEPH HENRY. 123 culiar to the iron, on account of its temporary magnetism ; but this idea was shown to be erroneous by substituting a Fie 5.—a represents coil No.1, } helix No. 1, and ¢ an interposed plate of metal. plate of zine of about the same size and thickness. With this the screening influence was exhibited as before. 59. After this a variety of substances was interposed in succession, namely, copper, lead, mercury, acid, water, wood, glass, &c.; and it was found that all the perfect conductors, such as the metals, produced the screening influence; but nonconductors, as glass, wood, &c., appeared to have no ef- fect whatever. 60. When the helix was separated from the coil by a dis- tance only equal to the thickness of the plate, a slight sensa- tion could be perceived even when the zine of #5 of an inch in thickness was interposed. This effect was increased by increasing the quantity of the battery current. If the thick- ness of the plate was diminished, the induction through it be- came more intense. Thus a sheet of tinfoil interposed pro- duced no perceptible influence; also four sheets of the same were attended with the same result. A certain thickness of metal is therefore required to produce the screening effect, and this thickness depends on the quantity of the current from the battery. 61. The idea occurred to me that the screening might, in some way, be connected with an instantaneous current in the plate, similar to that in the induction by magnetic rotation, discovered by M. Arago. The ingenious variation of this principle by Messrs. Babbage and Herschel, furnished me with a simple method of determining this point. 124 WRITINGS OF JOSEPH HENRY. [1838 62. A circular plate of lead was interposed, which caused the induction in the helix almost entirely to disappear. A slip of the metal was then cut out in the direction ofa radius of the circle, as is shown in Fig. 6. With the Cr plate in this condition, no screening .was pro- duced; the shocks were as intense as if the Fia. 6.—a rep- resents a lead Metal were not present. plate, of which 63, This experiment however is not entirely e sector 6 is i ; Z : cut out. satisfactory, since the action might have taken place through the opening of the lead; to obviate this ob- jection, another plate was cut in the same manner, and the two interposed with a glass plate between them, and so ar- ranged that the opening in the one might be covered by the continuous part of the other. Still shocks were obtained with undiminished intensity. 64. But the existence of a current in the interposed con- ductor was rendered certain by attaching the magnetizing spiral by means of two wires to the edge of the opening in the circular plate, as is shown in Fig. 7. By this arrange- mentthelatent current was drawn # out, and its direction obtained by the polarity of a needle placed in F1a. 7.—a represents a lead plate, the spiral at b. bi the magnetizing spiral. 65. This current was a second- ary one, and its direction, in conformity with the discovery of Dr. Faraday, was found to be the same as that of the primary current. 66. That the screening influence is in some way produced by the neutralizing action of the current thus obtained, will be clear, from the following experiment. The plate of zinc before mentioned, which is nearly twice the diameter of the helix, instead of being placed between the conductors, was put on the top of the helix, and in this position, although the neutralization was not as perfect as before, yet a great reduction was observed in the intensity of the shock. 67. But here a very interesting and puzzling question oc- curs. How does it happen that two currents, both in the same direction, can neutralize each other? I was at first 1838] WRITINGS OF JOSEPH HENRY. 125 disposed to consider the phenomenon as a case of real elec- trical interference, in which the impulses succeed each other by some regular interval. But if this were true the effect should depend on the length and other conditions of the current in the interposed conductor. In order to investigate this, several modifications of the experiments were instituted. 68. First a flat coil (No. 8) was interposed instead of the plates. When the two ends of this wereseparated, the shocks were received as if the coil were not present; but when the ends were joined, so as to form a perfect metallic circuit, no shocks could be obtained. The neutralization with the coil in this experiment was even more perfect than with the plate. 69. Again, coil No. 2,in the form of a ring, was placed not between the conductors, but around the helix. With this disposition of the apparatus, and the ends of the coil joined, the shocks were scarcely perceptible, but when the ends were separated, the presence of the coil has no effect. 70. Also when helix No. 1 and 2 were together submitted to the influence of coil No. 1, the ends of the one being joined, the other gave no shock. 71. The experiments were further varied by placing helix No. 2 within a hollow cylinder of sheet brass, and this again within coil No. 2in a manner similar to that shown in Fig. 12, which is intended to illustrate another experi- ment. In this arrangement the neutralizing action was ex- hibited, as in the case of the plate. 72. A hollow cylinder of iron was next substituted for the one of brass, and with this also no shocks could be obtained. 73. From these experiments it is evident that the neutral- ization takes place with currents in the interposed or ad- joining conductors of all lengths and intensities, and there- fore cannot, as it appears to me, be referred to the interfer- ence of two systems of vibrations. 74. This part of the investigation was, for a time, given up almost in despair, and it was not until new light had been obtained from another part of the inquiry, that any further advances could be made towards a solution of the mystery. 126 WRITINGS OF JOSEPH HENRY. [1838 75. Before proceeding to the next Section, I may here state that the phenomenon mentioned, paragraph 54, in ref- erence to helix No. 4, is connected with the neutralizing ac- tion. The electrical discharge having destroyed the insula- tion at some point, a part of the spires would thus form a shut circuit, and the induction in this would counteract the action in the other part of the helix; or in other words, the helix was in the same condition as the two helices mentioned in paragraph 70, when the ends of the wire of one were joined. 76. Also the same principle appears to have an important bearing on the improvement of the magneto-electrical ma- chine: since the plates of metal which sometimes form the ends of the spool containing the wire, must necessarily di- minish the action, and also from experiment of paragraph 72 the armature itself may circulate a closed current which will interfere with the intensity of the induction in the sur- rounding wire. I am inclined to believe that the increased effect observed by Sturgeon and Calland, when a bundle of wire is substituted fora solid piece of iron, is at least in part due to the interruption of these currents. I hope to resume this part of the subject, in connection with several other points, in another communication to the Society. 77. The results given in this Section may, at first sight, be thought at variance with the statements of Sir H. Davy, that needles could be magnetized by an electrical discharge with conductors interposed. But from his method of per- forming the experiment, it is evident that the plate of metal was placed between a straight conductor and the needle. The arrangement was therefore similar to the interrupted circuit in the experiment with the cut plate (62), which produces no screening effect. Had the plate been curved into the form of a hollow cylinder, with the two ends in contact, and the needle placed within this, the effect would have been otherwise. 1838] WRITINGS OF JOSEPH HENRY. 127 SECTION V. On the Production and Properties of induced Ourrents of the Third, Fourth, and Fifth order. 78. The fact of the perfect neutralization of the primary current by a secondary, in the interposed conductor, led me to conclude that if the latter could be drawn out, or separated from the influence of the former, it would itself be capable of producing a new induced current in a third conductor. 79. The arrangement exhibited in Fig. 8 furnishes a ready ESS "i Ain 11 a Fie. 8.—a coil No. 1, 6 coil No. 2, ¢ coil No. 3, d helix No. 1. means of testing this. The primary current, as usual, is passed through coil No. 1, while coil No. 2 is placed over this to receive the induction, with its ends joined to those of coil No. 3. By this disposition the secondary current passes through No. 3; and since this is at a distance, and without the influence of the primary, its separate induction will be rendered manifest by the effects on helix No.1. When the handles e, f, are grasped a powerful shock is received, prov- ing the induction of a tertiary current. 80. By asimilar but more extended arrangement, as shown in Fig. 9, shocks were received from currents of a fourth and fifth order; and with a more powerful primary current, and additional coils, a still greater number of successive induc- tions might be obtained. 81. The induction of currents of different orders, of suf- ficient intensity to give shocks, could scarcely have been anticipated from our previous knowledge of the subject. The secondary current consists as it were of a single wave 128 WRITINGS OF JOSEPH HENRY. [1838 of the natural electricity of the wire, disturbed but for an instant by the induction of the primary; yet this has the power of inducing another current, but little inferior in energy to itself, and thus produces effects apparently much greater in proportion to the quantity of electricity in motion than the primary current. 82. Some difference may be conceived to exist in the action of the induced currents, and that from the battery, since they are apparently different in nature; the one consisting, as we may suppose, of a single impulse, and the other of a succes- sion of such impulses, or a continuous action. It was there- fore important to investigate the properties of these curreuts, and to compare the results with those before obtained. 83. First, in reference to the intensity, it was found that with the small battery a shock could be given from the cur- rent of the third order to twenty-five persons joining hands; also shocks perceptible in the arms were obtained from a current of the fifth order. 84. The action at a distance was also much greater than could have been anticipated. In one experiment shocks from the tertiary current were distinctly felt through the tongue, when helix No. 1 was at the distance of eighteen inches above the coil transmitting the secondary current. 85. The same screening effects were produced by the in- terposition of plates of metal between the conductors of the different orders, as those which have been described in refer- ence to the primary and secondary currents. 86. Also when the long helix is placed over a secondary current generated in a short coil, and which is therefore, as we have before shown, one of quantity, a tertiary current of intensity is produced. 87. Again, when the intensity current of the last experi- ment is passed through a second helix, and another coil is placed over this, a quantity current is again produced. Therefore in the case of these currents, as in that of the pri- mary, a quantity current can be induced from one of intensity, and the converse. By the arrangement of the apparatus as shown in Fig. 9, these different results are exhibited at once. 1838] | WRITINGS OF JOSEPH HENRY. 129 The induction from coil No. 3 to helix No.1 produces an intensity current, and from helix No. 2 to coil No. 4 a quan- tity current. Fia. 9.—a coil No. 1, 6 coil No. 2, ec coil No. 3, d helix No. 1, e helix No. 2 and 3, f coil No. 4, and g magnetizing spiral. 88. If the ends of coil No. 2,as in the arrangement of Fig. 8, be united to helix No. 1 instead of coil No. 3, no shocks can be obtained; the quantity current of coil No. 2 appears not to be of sufficient intensity to pass through the wire of the long helix. 89. Also, no shocks can be obtained from the handles attached to helix No. 2, in the arrangement exhibited in Fig. c a Fie. 10.—a coil No. 1, 6 helix No. 1, c coil No. 3, and d helix No. 8. 10. In this case the quantity of electricity in the current from the helix appears to be too small to produce any effect, unless its power is multiplied by passing it through a con- ductor of many spires. 90. The next inquiry was in reference to the direction of these currents, and this appeared important in connection with the nature of the action. The experiments of Dr. Fara- day would render it probable, that at the beginning and ending of the secondary current, its induction on an adjacent Wire is in contrary directions, as is shown to be the case in the primary current. But the whole action of a secondary aia is so instantaneous, that the inductive effects at the 130 WRITINGS OF JOSEPH HENRY. [1838 beginning and ending cannot be distinguished from each other, and we can only observe a single impulse, which however may be considered as the difference of two impulses in opposite directions. 91. The first experiment happened to be made with a cur- rent of the fourth order. The magnetizing spiral (11) was attached to the ends of coil No. 4, Fig. 9, and by the polarity of the needle it was found that this current was in the same direction with the secondary and primary currents.* Bya too hasty generalization, I was led to conclude, from this experiment, that the currents of all orders are in the same direction as that of the battery current, and I was the more confirmed in this from the results of my first experiments on the currents of ordinary electricity. The conclusion however caused me much useless labor and perplexity, and was afterwards. proved to be erroneous. 92. By a careful repetition of the last experiment, in refer- ence to each current, the important fact was discovered, that there exists an alternation in the direction of the currents of the several orders, commencing with the secondary. This result was so extraordinary, that it was thought necessary to establish it by a variety of experiments. For this purpose the direc- tion was determined by decomposition, and also by the gal- vanometer, but the result was still the same; and at this stage of the inquiry I was compelled to the conclusion that the directions of the several currents were as follows: PIIMAry, CUELeMb ete eee eee eee ee ee -{- Secondary currentc sea see one oe ee ee eee Currentjof theithirdjorder.!-£. 22 ee ee Current of the founthvorden 22 =se 2 see ee vee @urrentiofithemitghyord erase ee 93. In the first glance at the above table, we are struck with the fact that the law of alternation is complete, except between the primary and secondary currents, and it appeared *Tt should be recollected that all the inductions which have been men- tioned were produced at the moment of breaking the circuit of the battery current. The induction at the formation of the current is too feeble to pro- duce the effects described. 1838] _ WRITINGS OF JOSEPH HENRY. 131 that this exception might possibly be connected with the induced current which takes place in the first coil itself, and which gives rise to the phenomena of the spiral conductor. If this should be found to be minus, we might consider it as existing between the primary and secondary, and the anomaly would thus disappear. Arrangements were therefore made to fully satisfy myself on this point. For this purpose the decomposition of dilute acid and the use of the galvanometer were resorted to, by placing the apparatus between the ends of a cross wire attached to the extremities of the coil, as in the arrangement described by Dr. Faraday (ninth series ;) but all the results persisted in giving a direction to this cur- rent the same as stated by Dr. Faraday, namely, that of the primary current. I was therefore obliged to abandon the supposition that the anomaly in the change of the current is connected with the induction of the battery current on itself. 94. Whatever may be the nature or causes of these changes in the direction, they offer a ready explanation of the neutra]- izing action of the plate interposed between two conductors, since a secondary current is induced in the plate; and although the action of this, as has been shown, is in the same direction as the current from the battery, yet it tends to induce a current in the adjacent conducting matter of a contrary direction. The same explanation is also applicable to all the other cases of neutralization, even to those which take place between the conductors of the several orders of currents. 95. The same principle explains some effects noted in reference to the induction of a current on itself. If a flat coil be connected with the battery, of course sparks will be produced by the induction, at each rupture of the circuit. But if in this condition another flat coil, with its ends joined, be placed on the first coil, the intensity of the shock is much diminished, and when the several spires of the two coils are mutually interposed by winding the two ribbons together into one coil, the sparks entirely disappear in the coil trans- mitting the battery current, when the ends of the other are joined. To understand this, it is only necessary to mention 132 WRITINGS OF JOSEPH HENRY. -[1838 that the induced current in the first coil is a true secondary current, and it is therefore neutralized by the action of the secondary in the adjoining conductor; since this tends to produce a current in the opposite direction. 96. It would also appear from the perfect neutralization which ensues in the arrangement just before described, that the induced current in the adjoining conductor is more powerful than that of the first conductor; and we can easily see how this may be. The two ends of the second coil are joined, and it thus forms a perfect metallic circuit; while the circuit of the other coil may be considered as partially interrupted, since to render the spark visible the electricity must be projected as it were through a small distance of air. 97. We would also infer that two contiguous secondary currents, produced by the same induction, would partially counteract each other. Moving in the same direction, they would each tend to induce a current in the other of an opposite direction. This is illustrated by the following ex- periment: helix No. 1 and 2 were placed together, but not united, above coil No. 1,so that they each might receive the induction; the larger was then gradually removed toa ereater distance from the coil, until the intensity of the shock from each was about the same. When the ends of the two were united, so that the shock would pass through the body from the two together, the effect was apparently less than with one helix alone. The result however was not as satisfactory as in the case of the other experiments; a slight difference in the intensity of two shocks could not be appreciated with perfect certainty. SECTION VI. The production of induced Currents of the different Orders from ordinary Electricity. 98. Dr. Faraday, in the ninth series of his researches, re- marks that “ the effect produced at the commencement and the end of a current (which are separated by an interval of time when that current is supplied from a voltaic apparatus) must occur at the same moment when a common electrical 1838] WRITINGS OF JOSEPH HENRY. 183 discharge is passed through a long wire. Whether if it happen accurately at the same moment they would entirely neutralize each other, or whether they would not still give some definite peculiarity to the discharge, is a matter re- maining to be examined.” 99. The discovery of the fact that the secondary current, which exists but for a moment, could induce another cur- rent of considerable energy, gave some indication that simi- lar effects might be produced by a discharge of ordinary electricity, provided a sufficiently perfect insulation could be obtained. 100. To test this a hollow glass cylinder, Fig. 11, of about 6 = = = || 5 ATR iitaai is Fia. 11.—a glass cylinder, 6 Leyden jar, c magnetizing spiral. six inches in diameter, was prepared with a narrow ribbon of tinfoil, about thirty feet long, pasted spirally around the outside, and a similar ribbon of the same length, pasted on the inside; so that the corresponding spires of the two were directly opposite each other. The ends of the inner spiral passed out of the cylinder through a glass tube, to prevent all direct communication between the two. When the ends of the inner ribbon were joined by the magnetizing spiral (11), containing a needle, and a discharge from a half gallon jar sent through the outer ribbon, the needle was strongly magnetized in such a manner as to indicate an induced cur- rent through the inner ribbon in the same direction as that of the current of the jar. This experiment was repeated many times, and always with the same result. 101. When the ends of one of the ribbons were placed very nearly in contact, a small spark was perceived at the 134 WRITINGS OF JOSEPH HENRY. [1838 opening, the moment the discharge took place through the other ribbon. 102. When the ends of the same ribbon were separated to a considerable distance, a larger spark than the last could be drawn from each end by presenting a ball, or the knuckle. 103. Also if the ends of the outer ribbon were united, so as to form a perfect metallic circuit, a spark could be drawn from any point of the same, when a discharge was sent through the inner ribbon. 104. The sparks in the two last experiments are evidently due to the action known in ordinary electricity by the name of the lateral discharge. To render this clear, it is perhaps necessary to recall the well known fact, that when the knob of a jar is electrified positively, and the outer coat- ing is connected with the earth, then the jar contains a small excess of positive electricity beyond what is necessary to perfectly neutralize the negative surface. Ifthe knob be put in communication with the earth, the extra quantity, or the free electricity, as it is sometimes called, will be on the negative side. When the discharge took place in the above experiments, the inner ribbon became for an instant charged with this free electricity, and consequently threw off from the outer ribbon, by ordinary induction, the sparks de- scribed. It therefore became a question of importance to determine whether the induced current described in para- graph 100 was not also a result of the lateral discharge, in- stead of being a true case of a secondary current analogous to those produced from galvanism. For this purpose the jar was charged, first with the outer coating in connection with the earth, and again with the knob in connection with the same, so that the extra quantity might be in the one case plus and in the other minus; but the direction of the in- duced current was not affected by these changes; it was always the same, namely, from the positive to the negative side of the jar. 105. When however the quantity of free electricity was increased, by connecting the knob of the jar with a globe about a foot in diameter, the intensity of magnetism ap- 1838] WRITINGS OF JOSEPH HENRY. 135 peared to be somewhat diminished, if the extra quantity was on the negative side; and this might be expected, since the free electricity, in its escape to the earth through the ribbon, in this case would tend to induce a feeble current in the op- posite direction to that of the jar. 106. The spark from an insulated conductor may be con- sidered as consisting almost entirely of this free or extra electricity, and it was found that this was also capable of producing an induced current, precisely the same as that from the jar. In the experiment which gave this result, one end of the outer ribbon of the cylinder (100) was con- ‘nected with the earth, and the other caused to receive a spark from a conductor fourteen feet long, and nearly a foot in diameter. The direction of the induced current was the same as that of the spark from the conductor. 107. From these experiments it appears evident that the discharge from the Leyden jar possesses the property of in- ducing a secondary current precisely the same as the gal- vanic apparatus, and also that this induction is only so far connected with the phenomenon of the lateral discharge as this latter partakes of the nature of an ordinary electrical current. 108. Experiments were next made in reference to the pro- duction of currents of the different orders by ordinary elec- tricity. For this purpose a second cylinder was prepared with ribbons of tinfoil, in a similar manner to the one before described. The two were then so connected that the second- ary current from the first would circulate around the second, When a discharge was passed through the outer ribbon of the first cylinder, a tertiary current was induced in the inner ribbon of the second. This was rendered manifest by the magnetizing of a needle in a spiral joining the ends of the last mentioned ribbon. 109. Also by the addition, in the same way, of a third cylinder, a current of the fourth order was developed. The same result was likewise obtained by using the arrangement of the coils and helices shown in Fig. 9. For these experi- ments however the coils were furnished with a double coat- 136 WRITINGS OF JOSEPH HENRY. [1838 ing of silk, and the contiguous conductors separated by a large plate of glass. 110. Screening effects precisely the same as those exhibited in the action of galvanism were produced by interposing a plate of metal between the conductors of different orders, Figures 8 and 9. The precaution was taken to place the plate between two frames of glass, in order to be assured that the effect was not due to a want of perfect insulation. 111. Also analogous results were found when the experi- ments were made with coils interposed instead of plates, as described in paragraph 68. When the ends of the inter- posed coils were separated, no screening was observed, but when joined, the effect was produced. The existence of the induced current, in all these experiments, was determined by the magnetism of a needle in a spiral attached to one of the coils. 112. Likewise shocks were obtained from the secondary current by an arrangement shown in Fig. 12. Helices No. ) Fia. 12.—a coil No. 2, 6 an inverted bell glass, ¢ helices No. 2 and 8. 2 and No. 8 united are put within a glass jar, and coil No. 2 is placed around the same. When the handles are grasped, a shock is felt at the moment of the discharge, through the outer coil. The shocks however were very different in in- tensity with different discharges from the jar. In some cases no shock was received, when again, with a less charge, a severe one was obtained. But these irregularities find an explanation in a subsequent part of the investigation. 118. In all these experiments, the results with ordinary and galvanic electricity are similar. But at this stage of the investigation there appeared what at first was considered a 1838] WRITINGS OF JOSEPH HENRY. 137 remarkable difference in the action of the two. I allude to the direction of the currents of the different orders. These, in the experiments with the glass cylinders, instead of ex- hibiting the alternations of the galvanic currents (92), were all in the same direction as the discharge from the jar, or in other words, they were all plus. 114. To discover, if possible, the cause of this difference, a series of experiments was instituted; but the first fact de- veloped, instead of affording any new light, seemed to ren- der the obscurity more profound. When the directions of the currents were taken in the arrangement of the coils (Fig. 9) the discrepancy vanished. Alternations were found the same as in the case of galuanism. This result was so extraordinary that the experiments were many times repeated, first with the glass cylinders, and then with the coils; the results how- ever were always the same. The cylinders gave currents all in one direction; the coils in alternate directions. 115. After various hypotheses had been formed, and in succession disproved by experiment, the idea occurred to me that the direction of the currents might depend on the dis- tance of the conductors, and this appeared to be the only difference existing in the arrangement of the experiments with the coils and the cylinders.* In the former the distance between the ribbons was nearly one inch and a half, while in the latter it was only the thickness of the glass, or about spth of an inch. 116. In order to test this idea, two narrow slips of tinfoil, about twelve feet long, were stretched parallel to each other, and separated by thin plates of mica to the distance of about ~jth of an inch. When a discharge from the half gallon jar was passed through one of these, an induced current in the same direction was obtained from the other. The ribbons were then separated, by plates of glass, to the distance of jth of an inch; the current was still in the same direction, or plus. When the distance was increased to about 4th of an inch, no induced current could be cbtained; and when they * This idea was not immediately adopted, because I had previously experi- mented on the direction of the secondary current from galvanism, and found no change in reference to distance. 138 WRITINGS OF JOSEPH HENRY. [1838 were still further separated the current again appeared, but was now found to have a different direction, or to be minus. No other change was observed in the direction of the current; the intensity of the induction decreased as the ribbons were separated. The existence and direction of the current, in this experiment, were determined by the polarity of the needle in the spiral attached to the ends of one of the ribbons. 117. The question at this time arose, whether the direc- tion of the current, as indicated by the polarity of the needle, was the true one, since the magnetizing spiral might itself, in some cases, induce an opposite current. To satisfy myself on this point a series of charges, of various intensity and quantity, from a single spark of the large conductor to the full charge of nine jars, were passed through the small spiral, which had been used in all the experiments, but they all gave the same polarity. The interior of this spiral is so small, that the needle is throughout in contact with the wire. 118. The fact of a change in the direction of the induced current by a change in the distance of the conductors, being thus established, a great number and variety of experiments were made to determine the other conditions on which the change depends. These were sought for ina variation of the intensity and quantity of the primary discharge, in the length and thickness of the wire, and in the form of the cir- cuit. The results were however in many cases anomalous, and are not sufficiently definite to be placed in detail before the Society. I hope to resume the investigation at another time, and will therefore at present briefly state only those general facts which appear well established. 119. With a single half gallon jar, and the conductors separated toa distance less than 5th of an inch, the in- duced current is always in the same direction as the primary. But when the conductors are gradually separated, there is always found a distance at which the current begins to change its direction. This distance depends certainly on the amount of the discharge, and probably on the intensity, and also on the length and thickness of the conductors. With a battery of eight half gallon jars, and parallel wires of about ten feet long, the change in the direction did not 1838] WRITINGS OF JOSEPH HENRY. 139 take place at a less distance than from twelve to fifteen inches, and with a still larger battery and longer conductors, no change was found, although the induction was produced at the distance of several feet. 120. The facts given in the last paragraph relate to the inductive action of the primary current; but it appears from the results detailed in paragraphs 110 and 114, that the currents of all the other orders also change the direction of the inductive influence with a change of the distance. In these cases however the change always takes place at a very small distance from the conducting wire; and in this re- spect the result is similar to the effect of a primary current from the discharge of a small jar. 121. The most important experiments, in reference to dis- tance, were made in the lecture room of my respected friend Dr. Hare of Philadelphia, with the splendid electrical appa- ratus described in the Fifth Volume (new series) of the Transactions of this Society. The battery consists of thirty- two jars, each of the capacity of a gallon. for the free electricity of the cloud. It is not however prob- able that the attraction, whatever may be its intensity, of so small a quantity of matter as that of the wire of the telegraph, can of itself produce an electrical discharge from the heavens, although, if the discharge were started by some other cause, such as the attraction of a large mass of conducting matter in the vicinity, the attraction of the wire might be sufficient to change the direction of the descending bolt, and draw it, in part or in whole, to itself. It should also be recollected, that on account of the perfect conduction, a discharge on anv part of the wire must affect every other part of the connected line, although it may be hundreds of miles in length. That the wire should give off a discharge to a number of poles in succession is a fact I should have expected from my previous researches on the lateral discharge of a conductor transmitting a current of free electricity. In a paper on this subject, presented to the British Association in 1837,* I showed that when electricity strikes a conductor explosively it tends to give off sparks to all bodies in the vicinity, how- ever intimately the conductor may be connected with the earth. In an experiment in which sparks from a small machine were thrown on the upper part of a lightning rod, erected in accordance with the formula given by the French Institute, corresponding sparks could be drawn from every part of the rod, even from that near the ground. In acommu- nication since made to this Society, I have succeeded in refer- ring this phenomenon to the fact, that during the transmission of a quantity of electricity along a rod, the surface of the conductor is charged in succession, as it were, by a wave of the fluid, which, when it arrives opposite a given point, tends to give off a spark to a neighboring body for the same reason * [Report of British Association, 1887. See ante, page 101.] 1846] WRITINGS OF JOSEPH HENRY. 247 that the charged conductor of the machine gives off a spark under the same circumstances. It might at first be supposed that the redundant electricity of the conductor would exhaust itself in giving off the first spark, and that a second discharge could not take place; but it should be observed that the wave of free electricity, in its passage, is constantly attracted to the wire by the portion of the uncharged conductor which immediately precedes its position at any time; and hence but a part of the whole redundant electricity is given off at one place, the velocity of transmission of the wave as it passes the neighboring body, and its attraction for the wire, preventing a full dis charge at any one place. The intensity of the successive explosions is explained by referring to the fact, that the dis- charge from the clouds does not generally consist of a single wave of electricity, but of a number of discharges along the same path in rapid succession, or of a continuous discharge. which has an appreciable duration; and hence the wire of the telegraph is capable of transmitting an immense quantity of the fluid thus distributed over a great length of the con- ductor. The remarkable facts of the explosions of the electricity into the air, and of the poles being struck in interrupted suc- cession, find a plausible explanation in another electrical principle which I have established, namely, in all cases of the disturbance of the equilibrium of the electrical plenum which we must suppose to exist throughout all terrestrial space, the state of rest is attained by a series of diminishing oscillations. Thus, ina discharge of a Leyden jar, I have shown that the phenomena exhibited cannot be explained by merely supposing the transfer of a quantity of fluid from the inner to the outer side of the jar; but in addition to this we are obliged to admit the existence of several waves, backwards and forwards, until the equilibrium is attained. In the case of the discharge from the cloud, a wave of the natural electricity of the metal is repelled each way from the point on which the discharge falls, to either end of the wire, is then reflected, and in its reverse passage meets in 248 WRITINGS OF JOSEPH HENRY. [1846 succession the several waves which make up the discharge from the cloud. These waves will therefore interfere at cer- tain points along the wire, producing, for a moment, waves of double magnitude, and will thus enhance the tendency of the fluid at these points to fly from the conductor. I do not say that the effects observed were actually produced in this way; I merely wish to convey the idea that known principles of electrical action might, under certain circum- stances, lead us to anticipate such results. 2. The state cf the wire may be disturbed by the conduc- tion of a current of electricity from one portion of space to another, without the presence of a thunder-cloud ; and this will happen in case of a long line, when the electrical con- dition of the atmosphere which surrounds the wire at one place is different from that at another. Now it is well known that a mere difference in elevation is attended with a change in the electrical state of the atmosphere. A conductor, elevated by means of a kite, gives sparks of positive electricity on a perfectly clear day; hence, if the line of the telegraph passes over an elevated mountain ridge, there will be con- tinually, during clear weather, a current from the more elevated to the lower points of the conductor. A current may also be produced in a long level line by the precipitation of, vapor, in the form of a fog, at one end, while the air remains clear at the other; or by the existence of a storm of rain or snow at any point along the line, while the other parts of the wire are not subjected to the same influence. Currents of sufficient power to set in motion the marking machine of the telegraph have been observed, which must have been produced by some of these causes. In one case the machine spontaneously began to operate without the aid of the battery while a snow-storm was falling at one end of the line, and clear weather existed at the other. On another occasion a continued stream of electricity was observed to pass between two points at a break in the wire, presenting the appearance of a gaslight almost extinguished. A con- 1846] WRITINGS OF JOSEPH HENRY. 249 stant effect of this kind indicates a constant accession of elec- tricity at one part of the wire, and a constant discharge at the other. 38. The natural electricity of the wire of the telegraph is liable to be disturbed by the ordinary electrical induction of a distant cloud. Suppose a thunder-cloud driven by the wind in such a direction as to cross one end of the line of the telegraph at the elevation—say of a mile; during the whole time of the approach of the cloud to the point of its path directly above the wire, the repulsion of the redundant elec- tricity with which it is charged would constantly drive more and more of the natural electricity of the wire to the farther end of the line, and would thus give rise to a current. When the cloud arrived at the point nearest to the wire, the current would cease for a moment; and as the repulsion gradually diminished by the receding of the cloud, the natural elec- tricity of the wire would gradually return to its normal state, giving rise to a current in an opposite direction. If the cloud were driven by the wind parallel to the line of the telegraph a current would be produced towards each end of the wire, and these would constantly vary in intensity with the different positions of the cloud. Although currents pro- duced in this way may be too. feeble to set in motion the marking apparatus, yet they may have sufficient power to influence the action of the current of the battery so as to interfere with the perfect operation of the machine. 4, Powerful electrical currents are produced in the wires of the telegraph by every flash of lightning which takes place within many miles of the line, by the action of dynamic induction; which differs from the action last described in being the result of the influence of electricity in motion on the natural electricity of the conductor. The effect of this induction, which is the most fruitful source of disturbance, will be best illustrated by an account of some experiments of my own, presented to the Society in 1843. A copper wire was suspended by silk strings around the ceiling of an upper 250 WRITINGS OF JOSEPH HENRY. [1846 room so as to form a parallelogram of about sixty feet by thirty on the sides; and in the cellar of the same building, immediately below, another parallelogram of the same dimen- sions was placed. When a spark from an electrical machine was transmitted through the upper parallelogram an induced current was developed in the lower one, sufficiently powerful to magnetize needles, although two floors intervened, and the conductors were separated to the distance of thirty feet. In this experiment no electricity passed through the floors from one conductor to the other; the effect was entirely due to the repulsive action of the electricity in motion in the upper wire on the natural electricity of the lower. In another experiment two wires, about 400 feet long, were stretched parallel to each other between two buildings; a spark of electricity sent through one produced a current in the other, though the two were separated to the distance of 300 feet; and from all the experiments it was concluded that the dis- tance might be indefinitely increased, provided the wires were lengthened in a corresponding ratio. That the same effect is produced by the repulsive action of the electrical discharge in the heavens is shown by the following modification of the foregoing arrangement. One of the wires was removed and the other so lengthened at one end as to pass into my study and thence through a cellar window into an adjacent well. With every flash of lightning, which took place in the heavens within at least a circle of twenty miles around Princeton, needles were magnetized in the study by the induced current developed in the wire. The same effect was produced by soldering a wire to the metallic roof of the house, and passing it down into the well; at every flash of lightning a series of currents, in alternate directions, was produced in the wire. I was also led, from these results, to infer that induced currents must traverse the line of a railroad, and this I found to be the case. Sparks were seen at the breaks in the con- tinuity of the rail with every flash of a distant thunder cloud. Similar effects, but in a greater degree, must be produced on the wire of the telegraph, by every discharge in the 1846] WRITINGS OF JOSEPH HENRY. 251 heavens; and the phenomena which I witnessed on the 19th of June in the telegraph office in Philadelphia were, I am sure, of this kind. Inthe midst of the hurry of the transmis- sion of the congressional intelligence from Washington to Philadelphia, and thence to New York, the apparatus began to work irregularly. The operator at each end of the line announced at the same time a storm at Washington, and another at Jersey City. The portion of the circuit of the telegraph which entered the building, and was connected with one pole of the galvanic battery, happened to pass within the distance of less than an inch of the wire which served to form the connection of the other pole with the earth. Across this space, at an interval of every few minutes, a series of sparks in rapid succession was observed to pass ; and when one of the storms arrived so near Philadelphia that the lightning could be seen, each series of sparks was found to be simultaneous with a flash in the heavens. Now we cannot suppose, for a moment, that the wire was actually struck at the time each flash took place; and indeed it was observed that the sparks were produced when the cloud and flash were at a distance of several miles to the east of the line of the wire. The inevitable conclusion is that all the exhibition of electrical phenomena witnessed during the afternoon was purely the effects of induction, or the mere disturbance of the natural electricity of the wire at a distance, without any transfer of the fluid from the cloud to the apparatus. The discharge between the two portions of the wire con- tinued for more than an hour, when the effect became so powerful that the superintendent, alarmed for the safety of the building, connected the long wire with the city gas pipes, and thus transmitted the current silently to the ground. I was surprised at the quantity and intensity of the current; it is well known that to affect a common galvanometer with ordinary electricity requires the discharge of a large battery ; but such was the quantity of the induced current exhibited on this occasion that the needle of an ordinary vertical gal- vanometer, with a short wire, and apparently of little sensi- bility, was moved several degrees. 252 WRITINGS OF JOSEPH HENRY. [1846 The pungency of the spark was also, as might have been expected, very great. When a small break was made in the circuit, and the parts joined by the forefinger and thumb the discharge transmitted through the hand affected the whole arm up to the shoulder. I was informed by the superintendent that on another occasion a spark passed over the surface of the spool of wire surrounding the legs of the horse-shoe magnet at right angles to the spires; and such was its intensity and quantity that all the wires across which it passed were melted at points in the same straight line as if they had been cut in two by a sharp knife. The effects of the powerful discharges from the clouds may be prevented, in a great degree, by erecting at intervals along the line, and aside of the supporting poles, a metallic wire connected with the earth at the lower end, and terminating above at the distance of about half an inch from the wire of the telegraph. By this arrangement the insulation of the conductor will not be interfered with, while the greater portion of the charge will be drawn off. I think this pre- caution of great importance at places where the line crosses a river, and is supported on high poles. Also in the vicinity of the office of the telegraph where a discharge, falling on the wire near the station, might send a current into the house of sufficient quantity to produce serious accidents. The fate of Professor Richman, of St. Petersburg, should be recollected, who was killed by a flash from a small wire, which entered his house from an elevated pole, while he was experimenting on atmospheric electricity. The danger however which has been apprehended from the electricity leaving the wire and discharging itself into a person on the road is, I think, very small; electricity, of sufficient intensity to strike a person at the distance of eight or ten feet from the wire, would, in preference, be conducted down the nearest pole. It will however in all cases be most prudent to keep at a proper distance from the wire during the existence of a thunder storm in the neighborhood. | 8 1846] WRITINGS OF JOSEPH HENRY. 253 It may be mentioned as an interesting fact, derived from two independent sources of information, that large numbers of small birds have been seen suspended by the claws from the wire of the telegraph. They had, in all probability, been instantaneously killed, either by a direct discharge, or an induced current from a distant cloud while they were rest- ing on the wire. Though accidents to the operators, from the direct dis- charge, may be prevented by the method before mentioned, yet the effect on the machine cannot be entirely obviated; the residual current which escapes the discharge along the perpendicular wires must neutralize, for a moment, the cur- rent of the battery, and produce irregularity of action in the apparatus. The direct discharge from the cloud on the wire is, com- paratively, not a frequent occurrence, while the dynamic inductive influence must be a source of constant disturbance during the seasons of thunder storms; and no other method presents itself to my mind at this time for obviating the effect, but that of increasing the size of the battery, and diminishing the sensibility of the magnet so that at least the smaller induced currents may not be felt by the machine. It must be recollected that the inductive influence takes place at a distance through all bodies, conductors and non- conductors; and hence no coating that can be put upon the wire will prevent the formation of induced currents. I think it-not improbable, since the earth has been made to act the part of the return conductor, that some means will be discovered for insulating the single wire beneath the sur- face of the earth; the difficulty in effecting this is by no means as great as that of insulating two wires, and prevent- ing the current striking across from one to the other. A wire buried in the earth would be protected in most cases from the effect of a direct discharge; but the inductive in- fluence would still be exerted, though perhaps in a less degree. The wires of the telegraph are too small and too few in number to affect, as some have supposed, the electrical con- 254 WRITINGS OF JOSEPH HENRY. [1846 dition of the atmosphere by equalizing the quantity of the fluid in different places, and thus producing a less change- able state of the weather. The feeble currents of electricity which must be constantly passing along the wires of a long line may however, with proper study, be the means of dis- covering many interesting facts relative to the electrical state of the air over different regions.* ON THE “FOUNTAIN-BALL,’ AND ON THE INTERFERENCE OF HEAT. (Proceedings of the American Philosophical Society, vol. Iv, p. 285.) October 16, 1846. Professor Henry laid before the Society the results of some investigations that he had lately made on two questions in physical science, and a theory of the causes of the phenomena observed. The well known phenomenon of a ball resting on a jet of water he ascribed to the action of three different causes: 1st, to the adhesion of the water to the ball: 2d, to the adhesion of the water to itself: 3d, to the tendency of water to move in a straight line and also to the principle of action and re-action. He had also made experiments in regard to the interfer- ence of heat for the purpose of discovering whether certain phenomena of interference of light were exhibited as well in the case of heat. He found it to be so, and that two rays of heat may be thrown on each other so as to produce a reduc- tion of temperature. *[Re-printed in Silliman’s American Journal of Science, 1847, vol. 111, pp. 25-382. Also in the London and Edinburgh Philosophical Magazine, 1847, vol. xxx, pp. 186-194.] 1846] WRITINGS OF JOSEPH HENRY. 255 ON THE ATOMIC CONSTITUTION OF MATTER. (Proceedings of the American Philosophical Society, vol. Iv, pp. 287-290.) November 6, 1846. The reference to a paper presented at the preceding meet- ing of the Society led Professor Henry to make some remarks on the corpuscular hypothesis of the constitution of matter. He stated that this subject has occupied attention at every period of the history of science, and though at first sight speculations of this kind might appear to belong exclusively to the province of the imagination, yet in reality he con- sidered this hypothesis a fruitful source of valuable additions to our knowledge of the actual phenomena of the physical world. Though simple insulated facts may occasionally be stumbled upon by a lucky accident, the discovery of a series of facts or of a general scientific principle is in almost all cases the result of deductions from a rational antecedent hypothesis, the product of the imagination—founded it is true on a clear analogy with modes of physical action the truth of which have been established by previous investigation. In constructing an hypothesis of the constitution of matter the simplest assumption, and indeed the only one founded on a proper physical analogy, is that the same laws of force and motion which govern the phenomena of the action of matter in masses pertains to the minutest atoms of these masses. It isa well established fact that portions of matter at a distance tend to approach each other, and when they are brought very near, to separate, and still nearer, again to approach, and so on through several alternations. In the present state of science we consider these actions as ultimate facts to which we give the name of attracting and repelling forces, and without attempting to go behind them we may study their laws of variation as to intensity and direction under different circumstances and particularly in reference to a change of distance. Bodies or masses of matter are also subjected to fixed laws of motion which have been classed 256 WRITINGS OF JOSEPH HENRY. [1846 under three heads, namely, the law of inertia or tendency to resist a change of state and to move in astraight line with a constant velocity, the law of the co-existence of separate motions, and the law of the equality of action and reaction. The explanation of a mechanical phenomenon consists in its analysis and the reference of its several parts to the fore- going laws of force and motion, and as no phenomenon, whether it relates to masses or the minutest portions of matter is fully explained until it can be referred to one or more of these laws it follows that any corpuscular hypothesis which does not ascribe to each atom of matter the property of obedience to the same laws must be defective. It was for this reason that in printing a syllabus of his lectures about two years ago he was induced to make some additions to the assumptions on which the corpuscular hypothesis of Bosco- vich is founded. According to this celebrated hypothesis, a portion of matter consists of an assemblage in space of an indefinite number of points kept at a given distance by attracting and repelling forces: these points have relative position but not magnitude, and are merely centers of action of the forces which affect our senses, and since all our knowl- edge of matter is derived from the action of these forces, to infer that these points are anything more than the centers of forces is going beyond our premises. This hypothesis readily explains the statical properties of bodies, such as elasticity, porosity, impenetrability, solidity, liquidity, crystallization, resistance to compression when a force is apphed to either side of the body, etce.; but it fails to account for the dynamic phenomena of masses of matter, or those which are referable to the three laws of motion. It is not therefore enough that we assume, as the elements of matter, an assemblage of points in space from which merely emanate attracting and repelling forces; we must also suppose these points to be endowed with inertia, or a ten- dency to resist a change of state, whether of rest or motion, and a tendency to move in a straight line; also to possess the property of preserving the effects of a number of im- pulses, as well as that of transferring motion from one point 1846] : WRITINGS OF JOSEPH HENRY. 257 to another, the one losing as much motion as the other gains. But the admission of the existence of points with such qual- ities brings us back to the Newtonian hypothesis of matter. According to the view we have given, a portion of matter consists of an assemblage of indivisible and indestructible atoms endowed with attracting and repelling forces, and with the property of obedience to the three laws of motion. All the other properties, and indeed all the mechanical phe- nomena of matter, so far as they have been analyzed, are probably referable to the action of such atoms, arranged in groups of different orders, namely, of ultimate atoms, chem- ical atoms, simple molecules, compound molecules, particles, etc.; the distance in all cases between any two atoms being much greater than the diameter of the atoms or molecules. In order that we may bring all the phenomena of the “im- ponderable” agents of nature, (as they are called,) under the category of the laws of force and motion, we are obliged to assume the existence of an etherial medium formed of atoms, which are endowed with precisely the same properties as those we have assigned to common matter ; and this assump- tion leads us to the inference, that matter is diffused through all space. That something exists between us and the sun, possessing the properties of matter, may be inferred from the simple fact that time is required for the transmission of light and heat through the intervening space. The phenomena of the transmitted motion, in these cases, are perfectly represented by undulations, in a medium composed of very minute atoms of ordinary matter, endowed with all the mechanical prop- erties we have mentioned. Indeed,the motion isanalogous— though not precisely similar—to the transmission of sound through air; the time however in the two cases being very different. Light passes the space between us and the sun in about eight minutes, while sound (through air) would require 13% years to perform the same journey. This difference in velocity is however readily explained by a difference in den- sity and elasticity of air, and the etherial medium. That the phenomena of light and heat from the sun are not the AW 258 WRITINGS OF JOSEPH HENRY. [1846 effect of transmission of mere force, (without intervening matter,) such as that of attraction and repulsion, is evident from the fact that these actions require no perceptible time for their transmission to the most distant part of the solar system. If the sun were at once to be annihilated the planet Neptune would, at the same instant begin to move in a tan- gent to its present orbit. Also, the phenomena of electricity and magnetism involve the consideration of time; the dis- charge of the former through a copper wire is transmitted with about the velocity of light, and the development of the latter in an iron bar is attended with a change in the ponderable molecules of the metal which requires time for its completion. According to the foregoing rules, we may assume with Newton, the existence of one kind of matter diffused through- out all space, and existing in four states, namely, the zethe- rial, the aériform, the liquid, and the solid. This method of presenting the atomic hypothesis of the constitution of mat- ter, may at first sight appear startling; but on a little re- flection, it will be found a necessary consequence of the attempt to explain the mechanical phenomena of matter by an assemblage of separateatoms. It may be objected to the assumption of one kind of matter that the fact of the im- ponderable nature of light, heat, electricity and magnetism require at least two kinds of matter; but if we adopt the theory of undulation, the phenomena of the “imponderables” (as they are called) are merely the results of the motions of the atoms of the etherial medium combined in some cases with the motion of the atoms of the body ; and since the vi- brations of the atoms of a mass of matter do not increase the attraction of the earth on the mass, an increase of tempera- ture in a body cannot change its weight ; and also because the etherial medium fills all space, a portion of this medium can no more exhibit weight than a quantity of air when weighed in the midst of the atmosphere. The points here noticed, relate merely to the fundamental conceptions of the corpuscular or atomic constitution of matter, and not to the arrangement of the atoms into sys- 1846] WRITINGS OF JOSEPH HENRY. 259 tems of groups, which are necessary to represent the varied and complicated mechanical and chemical phenomena ex- hibited in the physical changes going on around us. Though he could not at this time attempt to give any details of ap- plication of this hypothesis, he drew attention to one class of facts of which it is important to furnish an expression in the arrangement of the atoms. He alluded to the facts of polarity, or those which exhibit the action of opposite forces at the extremities of molecules or of masses. The north and south poles of two magnets, brought together, neutralize each other; the attraction of one is balanced by the repul- sion of the other, and the point of junction is without action on a third ferruginous body. In the same manner appar- ently, two chemical elements which enter into combination ~ exhibit a neutralizing effect, which indicates the existence of polar forces in the phenomena of chemical action. Noth- ing however is perceptible of this kind in the effects of gravi- tation; the action of two particles on each other does not interfere with the action at the same time of these two on any number of other particles. In conclusion it should be remembered that the legitimate use of speculations of this kind is not to furnish plausible explanations of known phenomena, or to present old knowl- edge in a new and more imposing dress, but to serve the higher purpose of suggesting new experiments and new phe- nomena, and thus to assist in enlarging the bounds of science and extending the power of mind over matter; and unless the hypothesis can be employed in this way, however much ingenuity may have been expended in its construction, it can only be considered as a scientific romance worse than useless, since it tends to satisfy the mind with the semblance of truth, and thus to render truth itself less an object of desire. 260 WRITINGS OF JOSEPH HENRY. [1846 ON THE HEIGHT OF THE AURORA. (Proceedings of the American Philosophical Society, vol. Iv, p. 870.) December 3d, 1846. Professor Henry made a communication relative to some observations on the aurora borealis, with the object of deter- mining the height of the meteor. The result of the observa- tions tended to establish the fact that the arch of the aurora like the rainbow isa local phenomenon, each observer seeing a different object. SCIENTIFIC WRITINGS OF JOSEPH HENRY. PARE Er, From 1847 ro 1878. (261) bea “AA HAO TO eye Oi AAs . SS te) Rng DS «SL a } Pinkie eas ih ahs ae f ‘Cus ’ i el ' Th cal wien OF Vee ‘ ‘ ; f be P . J ; a : 1 i 6) ~ ‘ Sb Bin Fh ui ies | Ov) Dea F : ! Pp i i a ye a } r yi y ry ae SCIENTIFIC PAPERS AND ABSTRACTS. PROGRAMME OF ORGANIZATION OF THE SMITHSONIAN INSTITUTION. (From the First Annual Report of the Secretary to the Board of Regents.)* December 8, 1847. GENTLEMEN: - - - In accordance with my instructions I consulted with men of eminence in the different branches of literature and science, relative to the details of the plan of organization, and arranged the various suggestions offered in the form of the accompanying programme. This, after having been submitted to a number of persons in whose knowledge and judgment I have confidence, is now pre- sented to the Board, with the concurrence of the Committee on Organization, for consideration and provisional adoption. I regret that I could not give the names of those whose sug- gestions have been adopted in the programme; the impos- sibility of rendering justice to all has prevented my attempt- ing this. Many of the suggestions have been offered by different persons independently of each other. - - - The introduction to the programme contains a series of propositions suggested by a critical examination of the will of Smithson, to serve as a guide in judging of the fitness of any proposed plan for carrying out the design of the tes- tator. - - - That all the propositions will meet with general approval cannot be expected; and that this organization is the best that could be devised is neither asserted nor believed. To produce @ priori a plan of organization which shall be found *[The Plan adopted by the Board of Regents, December 13, 1847.] (263) 264 WRITINGS OF JOSEPH HENRY. [1847 to succeed perfectly in practice, and require no amendment, would be difficult under the most favorable circumstances, and becomes almost impossible where conflicting opinions are to be harmonized and the definite requirements of the Act of Congress establishing the Institution are to be ob- served. It is not intended that the details of organization as given in the programme, should be permanently adopted without careful trial; they are rather presented as sugges- tions to be adopted provisionally, and to be carried into operation gradually and cautiously, with such changes from time to time as experience may dictate. INTRODUCTION. General considerations which should serve as a guide in adopting a Plan of Organization. 1. Will of Smithson. The property is bequeathed to the United States of America, “to found at Washington, under the name of the Smithsonian Institution, an establishment for the increase and diffusion of knowledge among men.” 2. The bequest is for the benefit of mankind. The Gov- ernment of the United States is merely a trustee to carry out the design of the testator. 3. The Institution is not a national establishment, as is frequently supposed, but the establishment of an individual, and is to bear and perpetuate his name. 4. The objects of the Institution are—1st, to increase—and 2d, to diffuse—knowledge among men. 5. These two objects’ should not be confounded with one another. The first is to enlarge the existing stock of knowl- edge by the addition of new truths; and the second, to dis- seminate knowledge, thus increased, among men. 6. The will makes no restriction in favor of any partic- ular kind of knowledge; hence all branches are entitled to a share of attention. 7. Knowledge can be increased by different methods of facilitating and promoting the discovery of new truths; and 1847] WRITINGS OF JOSEPH HENRY. 265 can be most extensively diffused among men by means of the press. 8. To effect the greatest amount of good, the organization should be such as to enable the Institution to produce re- sults in the way of increasing and diffusing knowledge, which cannot be produced either at all or so efficiently by the existing institutions in our country. 9. The organization should also be such as can be adopted provisionally, can be easily reduced to practice, receive mod- ifications, or be abandoned in whole or in part, without a sacrifice of the funds. 10. In order to compensate, in some measure, for the loss of time occasioned by the delay of eight years in establish- ing the Institution, a considerable portion of the interest which has accrued should be added to the principal. 11. In proportion to the wide field of knowledge to be cul- tivated, the funds are small. Economy should therefore be consulted in the construction of the building; and not only the first cost of the edifice should be considered, but also the continual expense of keeping it in repair, and of the support of the establishment necessarily connected with it. There should also be but few individuals permanently employed by the Institution. 12. The plan and dimensions of the building should be determined by the plan of the organization, and not the converse. 13. It should be recollected that mankind in general are to be benefited by the bequest, and that therefore all un- necessary expenditure on local objects would be a perver- sion of the trust. 14. Besides the foregoing considerations, deduced imme- diately from the will of Smithson, regard must be had to certain requirements of the act of Congress establishing the Institution. These are, a library, a museum, and a gallery of art, with a building on a liberal scale to contain them. 266 WRITINGS OF JOSEPH HENRY. [1847 SECTION I. Plan of Organization of the Institution in accordance with the foregoing deductions from the will of Smithson. To increase knowledge: It is proposed— 1. To stimulate men of talent to make original researches by offering suitable rewards for memoirs containing new truths; and, 2. To appropriate annually a portion of the income for particular researches, under the direction of suitable persons. To diffuse knowledge: It is proposed— 1. To publish a series of periodical reports on the progress of the different branches of knowledge; and, 2. To publish occasionally separate treatises on subjects of general interest. DETAILS OF THE PLAN TO INCREASE KNOWLEDGE. I. By stimulating researches. 1. Rewards consisting of money, medals, &c., offered for original memoirs on all branches of knowledge. * 2. The memoirs thus obtained to be published in a series of volumes, in a quarto form, and entitled “Smithsonian Contributions to Knowledge.” 3. No memoir on subjects of physical science to be accepted for publication which does not furnish a positive addition to human knowledge, resting on original research; and all unverified speculations to be rejected. 4. Each memoir presented to the Institution to be sub- mitted for examination to a commission of persons of reputation for learning in the branch to which the memoir pertains, and to be accepted for publication only in case the report of this commission is favorable. 5. The commission to be chosen by the officers of the Institution, and the name of the author (as far as practicable) concealed, unless a favorable decision be made. *[{In the annual report for 1855, this clause was changed to read— ‘1. Facilities afforded for the production of original memoirs on all branches of knowledge.’’] 1847] WRITINGS OF JOSEPH HENRY. 267 6. The volumes of the memoirs to besexchanged for the transactions of literary and scientific societies, and copies to be given to all the colleges and principal libraries in this country. One part of the remaining copies may be offered for sale, and the other carefully preserved, to form complete sets of the work, to supply the demand from new institutions. 7. An abstract, or popular account of the contents of these memoirs to be given to the public through the annual report of the Regents to Congress. II. By appropriating a part of the income annually to special objects of research. 1. The objects and the amount appropriated to be recom- mended by counsellors of the Institution. 2. Appropriations in different years to different objects; so that in course of time each branch of knowledge may receive a share. 3. The results obtained from these appropriations to be published, with the memoirs before mentioned, in the vol- umes of the “Smithsonian Contributions to Knowledge.” 4. Examples of objects for which appropriations may be made: (a.) System of extended meteorological observations for solving the problem of American storms. (6.) Explora- tions in descriptive natural history, and geological, magnet- ical, and topographical surveys, to collect materials for the formation of a Physical Atlas of the United States. (c.) Solution of experimental problems, such as a new determina- tion of the weight of the earth, of the velocity of electricity, and of light; chemical analyses of soils and plants; collection and publication of scientific facts accumulated in the offices of Government. (d.) Institution of statistical inquiries with reference to physical, moral, and political subjects. (e.) His- torical researches and accurate surveys of places celebrated in American history. (f.) Ethnological researches, particu- larly with reference to the different races of men in North America; also explorations and accurate surveys of the mounds and other remains of the ancient people of our country. 268 WRITINGS OF JOSEPH HENRY. [1847 \ DETAILS OF THE PLAN FOR DIFFUSING KNOWLEDGE. I. By the publication of a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge not strictly profes- sional. 1. These reports will diffuse a kind of knowledge generally interesting, but which at present is inaccessible to the public. Some of the reports may be published annually, others at longer intervals, as the ineome of the Institution or the changes in the branches of knowledge may indicate. 2. The reports are to be prepared by collaborators eminent in the different branches of knowledge. 3. Each collaborator to be furnished with the journals and publications, domestic and foreign, necessary to the compila- tion of his report; to be paid a certain sum for his labors, and to be named on the title-page of the report. 4, The reports to be published in separate parts so that persons interested in a particular branch can procure the parts relating to it without purchasing the whole. 5. These reports may be presented to Congress for partial distribution, the remaining copies to be given to literary and scientific institutions, and sold to individuals for a moderate price.* II. By the Publication of separate treatises on subjects of gen- eral interest. 1. These treatises may occasionally consist of valuable memoirs, translated from foreign languages, or of articles *The following are some of the subjects which may be embraced in the reports: I. PuystcaL Cuiass.—l. Physics, including astronomy, natural philos- ophy, chemistry and meteorology. 2. Natural history, including botany, zoology, geology, &c. 38. Agriculture. 4. Application of science to arts. II. Morat anv PouitTicat Ciass.—5. Ethnology, including particular history, comparative philology, antiquities, &c. 6. Statistics and political economy. 7. Mental and moral philosophy. 8. Asurvey of the political events of the world; penal reform, &c. III. LireratTuRE AND THE FinE Arts.—9. Modern literature. 10, The fine arts and their application to the useful arts. 11. Bibliography. 12. Obituary notices of distinguished individuals. 1847] WRITINGS OF JOSEPH HENRY. 269 prepared under the direction of the Institution, or procured by offering premiums for the best exposition of a given sub- ject. 2. The treatises should in all cases be submitted to a com- mission of competent judges previous to their publication. 3. As examples of these treatises, expositions may be ob- tained of the present state of the several branches of know]- edge mentioned in the table ofreports. Also of the following subjects, suggested by the Committee on Organization, viz: the statistics of labor, the productive arts of life, public in- struction, &c. SECTION II. Plan of Organization, in accordance with the terms of the resolu- tions of the Board of Regents, providing for the two modes of increasing and diffusing knowledge. 1. The Act of Congress establishing the Institution con- templated the formation of a library and a museum; and the Board of Regents, including these objects in the plan of organization, resolved to divide the income into two equal parts. 2. One part to be appropriated to increase and diffuse knowledge by means of publications and researches, agree- ably to the scheme before given. The other part to be ap- propriated to the formation of a library and a collection of objects of nature and of art. 3. These two plans are not incompatible with one another. 4. To carry out the plan before described, a library will be required, consisting, 1st, of a complete collection of the transactions and proceedings of all the learned societies in the world; 2d, of the more important current periodical publications, and other works necessary in preparing the periodical reports. 5. The Institution should make special collections, par- ticularly of objects to verify its own publications. 6. Also a collection of instruments of research in all branches of experimental science. 270 WRITINGS OF JOSEPH HENRY. [1847 7. With reference to the collection of books, other than those mentioned above, catalogues of all the different libra- ries in the United States should be procured, in order that the valuable books first purchased may be such as are not to be found in the United States. 8. Also catalogues of memoirs and of books in foreign libraries, and other materials, should be collected for ren- dering the Institution a centre of bibliographical knowledge, whence the student may be directed to any work which he may require. 9. It is believed that the collections in natural history will increase by donations as rapidly as the income of the Institution can make provision for their reception, and there- fore it will seldom be necessary to purchase any articles of this kind. 10. Attempts should be made to procure for the gallery of art, casts of the most celebrated articles of ancient and modern sculpture. 11. The arts may be encouraged by providing a room free of expense for the exhibition of the objects of the Art-Union, and other similar societies. 12. A small appropriation should annually be made for models of antiquities, such as those of the remains of ancient temples, &c. 13. For the present, or until the building is fully com- pleted, besides the Secretary, no permanent assistant will be required, except one to act as librarian. 14. The duty of the Secretary will be the general super- intendence—with the advice of the Chancellor and other members of the establishment—of the literary and scientific operations of the Institution; to give to the Regents annually an account of all of the transactions; of the memoirs which have been received for publication; of the researches which have been made; and to edit, with the assistance of the librarian, the publications of the Institution. 15. The duty of the Assistant Secretary, acting as libra- rian, will be, for the present, to assist in taking charge of the collections, to select and purchase, under the direction of 1847] WRITINGS OF JOSEPH HENRY. 271 the Secretary and a committee of the Board, books and cata- logues, and to procure the information before mentioned ; to give information on plans of libraries, and to assist the Secretary in editing the publications of the Institution and in the other duties of his office. 16. The Secretary and his assistants, during the session of Congress, will be required to illustrate new discoveries in science, and to exhibit new objects of art; also distinguished individuals should be invited to give lectures on subjects of general interest. 17. When the building is completed, and when in accord- ance with the act of Congress, the charge of the National Museum is given to the Smithsonian Institytion, other as- sistants will be required.* Explanation and Illustration of the Programme. Though the leading propositions of the Programme have been fully discussed by the Board, yet it will be important to offer some remarks in explanation and illustration of them in their present connection. That the Institution is not a national establishment, in the sense in which institutions dependent on the Govern- ment for support are so, must be evident when it is recol- lected that the money was not absolutely given to the United States, but intrusted to it for a special object, namely: the establishment of an institution for the benefit of men, to bear the name of the donor, and consequently to reflect upon his memory the honor of all the good which may be accomplished by means of the bequest. The operations of the Smithsonian Institution ought therefore to be mingled as little as possible with those of the Government, and its funds should be applied exclusively and faithfully to the increase and diffusion of knowledge among men. That the bequest is intended for the benefit of men in general, and that its influence ought not to be restricted to a * [Re-printed in Silliman’s American Journal of Science, September, 1848, vol. vi (2d series), pp. 288-292. ] 272 WRITINGS OF JOSEPH HENRY. [1847 single district, or even nation, may be inferred not only from the words of the will, but also from the character of Smith- son himself; and I beg leave to quote from a scrap of paper in his own hand the following sentiment bearing on this point: “The man of science has no country; the world is his country—all men his countrymen.” ‘The origin of the funds, the bequest of a foreigner, should also preclude the adoption of a plan which does not, in the words of Mr. Adams, “ spread the benefits to be derived from the institu- tion not only over the whole surface of this Union, but throughout the civilized world.” “ Mr. Smithson’s reason for fixing the seat of this institution at Washington obviously was, that there is the seat of Governmentof the United States, and there the Congress by whose legislation, and the Execu- tive through whose agency, the trust committed to the honor, intelligence, and good faith of the nation, is to be fulfilled.” The centre of operations being permanently fixed at Wash- ington, the’character of this city for literature and science will be the more highly exalted in proportion as the influ- ence of the Institution is more widely diffused. That the terms increase and diffusion of knowledge are logically distinct, and should be literally interpreted with reference to the will, must be evident when we reflect that they are used ina definite sense, and not as mere synonyms, by all who are engaged in the pursuits to which Smithson devoted his life. In England there are two classes of insti- tutions, founded on the two ideas conveyed by these terms. The Royal Society, the Astronomical, the Geological, the Statistical, the Antiquarian Societies, all have for their ob- ject the increase of knowledge; while the London Institution, the Mechanics’ Institution, the Surrey Institution, the Soci- ety for the Diffusion of Religious Knowledge, the Society forthe Diffusion of Useful Knowledge, are all intended to diffuse and disseminate knowledge among men. In our own country, also the same distinction is observed in the use of the terms by men of science. Our colleges, acade- mies, and common schools, are recognized as institutions partially intended for the diffusion of knowledge, while the 1847] WRITINGS OF JOSEPH HENRY. 273 express object of some of our scientific societies is the promo- tion of the discovery of new truths. The will makes no restriction in favor of any particular kind of knowledge; though propositions have been fre- quently made for devoting the funds exclusively to the pro- motion of certain branches of science having more imme- diate application to the practical arts of life, and the adoption of these propositions has been urged on the ground of the conformity of such objects to the pursuits of Smithson; but an examination of his writings will show that he excluded from his own studies no branch of general knowledge, and that he was fully impressed with the important philoso- phical fact that all subjects of human thought relate to one great system of truth. To restrict therefore the operations of the Institution to asingle science or art, would do injustice to the character of the donor, as well as to the cause of gen- eral knowledge. If preference is to be given to any branches of research, it should be to the higher and apparently more abstract; to the discovery of new principles rather than of isolated facts. And this is true even in a practical point of view. Agriculture would have forever remained an empir- ical art, had it not been for the light shed upon it by the atomic theory of chemistry; and incomparably more is to be expected as to its future advancement from the perfec- tion of the microscope than from improvements in the ordinary instruments of husbandry. The plan of increasing and diffusing knowledge, pre- sented in the first section of the programme, will be found in strict accordance with the several propositions deduced from the will of Smithson, and given in the introduction. It embraces, as a leading feature, the design of interesting the greatest number of individuals in the operations of the Institution, and of spreading its influence as widely as pos- sible. It forms an active organization, exciting all to make original researches who are gifted with the necessary power, and diffusing a kind of knowledge, now only accessible to the few, among all those who are willing to receive it. In this country, though many excel in the application of 18 274 WRITINGS OF JOSEPH HENRY. [1847 science to the practical arts of life, few devote themselves to the continued labor and patient thought necessary to the discovery and “development of new truths. The principal cause of this want of attention to original research, is the want, not of proper means, but of proper encouragement. The publication of original memoirs and periodical reports, as contemplated by the programme, will act as a powerful stimulus to the latent talent of our country, by placing in bold relief the real laborers in the field of original research, while it will afford the best materials for the use of those engaged in the diffusion of knowledge. The advantages which will accrue from the plan of pub- lishing the volumes of the Smithsonian Contributions to Knowledge, are various. In the first place, it will serve to render the name of the founder favorably known wherever literature and science are cultivated, and to keep it in con; tinual remembrance with each succeeding volume, as long as knowledge is valued. A single new truth, first given to the world through these volumes, will forever stamp their character as a work of reference. The contributions will thus form the most befitting monument to perpetuate the name of one whose life was devoted to the increase of knowledge, and whose ruling passion, strong in death, prompted the noble bequest intended to facilitate the labors of others in the same pursuit. Again, the publication of a series of volumes of original memoirs will afford to the Institution the most ready means of entering into friendly relations and correspondence with all the learned societies in the world, and of enriching its library with their current transactions and proceedings. But perhaps the most important effect of the plan will be that of giving to the world many valuable memoirs, which on account of the expense of the illustrations could not be otherwise published. Every one who adds new and im- portant truths to the existing stock of knowledge must be of necessity to a certain degree in advance of his age. Hence the number of readers and purchasers of a work is generally in the inverse ratio of its intrinsic value; and 1847] WRITINGS OF JOSEPH HENRY. 275 consequently authors of the highest rank of merit are fre- quently deterred from giving their productions to the world on account of the pecuniary loss to which the publication would subject them. When our lamented countryman, Bowditch, contemplated publishing his Commentary on La Place he assembled his family and informed them that the execution of this design would sacrifice one-third of his. fortune, and that it was proper his heirs should be con- sulted on a subject which so nearly concerned them. The answer was worthy the children of such a father: “We value,” said they, “your reputation more than your money.” Fortunately in this instance the means of making such a sacrifice existed, otherwise one of the proudest monuments of American science could not have been given to the world. In the majority of cases however those who are most capable of extending human knowledge are least able to incur the expense of the publication. Wilson, the Amer- ican ornithologist, states in a letter to Michaux that he has sacrificed everything to publish his work: “I have issued,” he says, “six volumes and am engaged on the seventh, but as yet I have not received a single cent of the proceeds.” In an address on the subject of natural history by one of our most active cultivators of this branch of knowledge we find the following remarks, which are directly in point: “Few are acquainted with the fact that from the small number of scientific works sold, and the great expense of plates, our naturalists not only are not paid for their labors but suffer pecuniary loss from their publications. Several works on different branches of zoology now in the course of publication will leave their authors losers by an aggre- gate of $15,000. I do not include in this estimate works already finished—one, for instance, the best contribution to the natural history of man extant, the publication of which will occasion its accomplished author a loss of several thou- sand dollars. 349 Earth, original heat of, indicated in many ways------ ----~-- ----- 153 Earths, different, heat absorbing capacity of ------ -------.------ 192 Earth’s induction shown by the electrical state of an insulated long AICO sears ese Ca a eee aS eae e 352, 354 Earth’s surface practically a slag, or burned out mass -._-- ---. ---- 88, 132 Easter, Dr., experiments by, on temperature expansion of sulphuric VCE oe ee ee eet ee Se 425 Eastward direction of atmospheric movements in the United States_ 290 Echo, aerial, hypothesis in explanation of ------------— -------- 524, 525 Echo dependent upon appreciable interval between a sound and its reflection ._-.---.---~---- ---. ---- ------------ ---= ---- ---- 409 35-2 546 ; INDEX. Pace Elastic force of vapor proportional to its density_------_- ---. -_-- 224 Elastic force of vapor, table of, at different temperatures ._..-__-- 217 Elasticity, an ultimate property of matter ---. ___. ---. .-.- --.. 94, 95 Electrical absorption and induction, instruments for observing ._-_ 358, 359 Electrical condition of an insulated long vertical rod ---.-_-_ -_-- 352 Hilectricalgimductyom abe SCT cclieeeet ee eee eee eee ee 328, 333 Electrical kite, observations with “2--- 2-— -22-2= -s2-__ = - 358, 359; 389 Electric discharge accompanied by a transfer of matter from con- COBY) pe ep I i a Ne ee el 336 Electric discharge tending mainly to surface of conductors -_____- 342 Electricity by Franklin’s theory, the postulated conditions of_-__- 312 Electricity from steam explained by Faraday ----_ ~---------- ae 347 Electricity, mechanical, more self-repellant than galvanism eaoeas 800,542 Electricity, positive and negative, method of distinguishing ______ 318, 329 Electricity referred to an action of the ether_--____-_-. ---__105, 3138, 346 Electricity, simple method of develope —__ ee 315 Electric tension increased by diminished surface in cloud condensa- (OP ee A Oe eee sees 860 Electro-magnetic bell signal devised at Albany in 1831 -_-__- -___ 434 Electro-magnetic telegraph first made operative by the “intensity ” PAN CE oe Ee co en te ele eel oe at ee RE Electro-magnetic telegraph, two systems of --_-_- _-__ ._-. -_--- 427 Electro-magnet with numerous close coils illustrated ~----. ---- = 429 Electrometer devised by Pettier, for measuring the force of elec- tricaljinduction: of the earthy see ee ee Dao Electroscope, simple forms of, illustrated _--__. -_---_. ---. ---- 317, 322, 328 Energy developed by the running down of organic compounds --_-- 118, 120 Energy developed from matter in a potential state __--__. -__-_ -. -.- 457 Energy of de-composition exactly equal to that of composition -__- 131 Epinus, theory by, of electric Maid oon ee aes ky oes Espy, Mr. James P., investigation by, on conditions of vapor FUOKO AS) CORO le a a a a epg Se 264 Espy, Mr. James P., investigation of tornadoes by------- ~~ 292, 293, 306 Espy, Mr. James P., meteorological labors of, highly commended- 442 Espy, Mr. James P., observations by, on the warming effect of at- DIMOSPINCTUC VA PVON aaa a ee ei Og OM Espy, Mr. James P., theory of storms by, not sufficiently appre- CLR CO sng a a ee eee 308 Espy, Mr. James P., views of, as to the compensation of wind cur- =) 01 ape a AEA ASA LPL SO US a te R ilo)! Equatorial belt of calms and rains illustrated ....---__.__ BESO Oa Calls: Equatorial rain-belt, oscillation of, with the seasons____-__- ~~ as 58 Equivalents, chemical, determining series of chemical compounds_ 110, 111 Evaporation greatly promoted by wind._....._...-. _____._-.__.. - 238 Evaporation not a probable cause of atmospheric electricity ~----- 346 Evaporation of water, method of estimating--._-..__.._--------_. 236, 239 INDEX. Evaporation proportional to the difference of tension between the water and the vapor in-the air... ._. . secre EL Expansion of air by increase of temperature ___.___._..._ Expansive effect resulting from the central rarefaction in tornadoes. Explosion, danger-from, in the use of petroleum lampets. wil8 6 Faraday, experiment by, on insulated metallic room ___. ___. _____ Faraday, explanation by, of the evolution of electricity from steam Faraday, remark by, on the electricity of chemical decomposition_ iPeagey es scCoures quoted <== seso nn oye soko a ~ es EPCE 112, Ferrel, Mr. W., observations by, of the air being heavier by loss of contrifupal TOUALLOM sere eet, ohne) een amine eres ape ae EiPh EOzeM.sTetaining vitality 20022 20 ONIN ee rt nl ey Fitzroy, Mauieal: direction by, of system of meteorology in Great Ber N Cir cee ee oo ee he eee mene oo MAIO Flashing test of the inflammability of petroleum described _____ Floods on upper rivers, importance of telegraphing, to lower parts Flourens, assumption by, of the SEL De) in tbat of organic (IES as i Ne ge Pr epee da ala Pt Fluidity of oils, relative, the method of estimating ________.____ Reswimwallevs, explanation Of, 2-22. 22ST 2 iomeainaeiecL On, Onclimate .o2 222222 be se Fossils, meteorological indications derived from --_. -----._--___- Foucault, M. Leon, apparatus by, for BeneraHing heat without con- WHO) Sa SSS SS ae ee ey a aS a eee ee See Fountain lamp employed in light-houses -_-_ -----.---_--__-.-.-. France, meteorological system established in__.-_.-_-. ----_. ____ Franklin, investigation of tornadoes by —---— -_---_ ---.-___ -_.- Franklin, observation by, on the travel of storms__-------___ -__- Franklin; theory by, of a single electric fluid ___. -____. -____L___. Fresnel, polarization of light explained by, through transverse vi- BacionerOretho mother 226 ts oS Bee 8 ee eee Funck, Mr. Joseph, improvement by, in lard-oil lamps ---- ------ Gages for rain and snow, observations on-_--— _--...------ ---- nee Gale, Dr. L. D., application by, of the ‘intensity’? magnet to the MIRO RUEIe eietp he aero oo ete eee ee cea ote eer Galvanic electricity less self-repellant than mechanical electricity - Gasparin, estimate by, of the annual consumption of carbon from the air-by vegetation .-_- -._----- --Le ee Gasparin, table by, of relative evaporation from water and earth_- Gas-pipes and water-pipes g good conductors for lightning ~~~ ---. - GS Thuscec and Biot, electrical observation by, in balloon ascent ~ Germination of plants effected by internal, not external, energy --- ‘ Globular lightning ’’ as-described- by Arago-- ~~ ---- -.-- ----~- Goodwin, Mr. William, assistance by, in lard-oil investigations__- 547 Pace. 50 1, 3, 427, 3386, 121, 548 INDEX. Green and Mason, observations by, on upper winds, in balloon SUS CO TUG ee cee Green, Mr. James, sulphuric acid barometer proposed by_-----_-- Gulf of Mexico the principal source of rain for the eastern portion of the United States) 6 so16coep ep tee eee sees Gulf-stream, effect of, on the climate of northwestern Europe-_-___ Hail-stones, the mode of formation of (222-25 (22s ae es Hall, Prof. James, notice by, of electro-magnetic bell signal at Albany an i682 oe os ee eee en eee eee Hamilton, Col. C. S., acknowledgment by, of the superiority of bE Ff) et pn ig I rr tn pep) Sele wk or Hamilton, Col. C. S., manufactory of rape-seed oil established by_ Hare, Dr. Robert, hypothesis by, as to the origin of atmospheric ClOCETICItYy soo eee LN ea i ee ee Hare, Dr. Robert, investigation of tornadoes by .----.----------- Harris, Sir W. Snow, arrangement by, of lightning-rods for ships- Harris, Sir W. Snow, experiment by, showing line of electric dis- Char ee ee oe eee ee eee ee oe eee Harris, Sir W. Snow, remark by, on the effect of lightning-rods__ Harrison, Mr., process by, of making ice artificially -----. ..--.._ Hawkins, Mr. C. D., account by, of thunder-storm at Key West hight-howse) 2 2 so ee ee ee ea Haziness of the air in ‘‘Indian summer”’ possibly due to smoke POM HD UTM TACOS as eee ee eee een eee Heat, absorption of, may be increased by interposed screen —--~--- Heat, accumulation of, under glass cover -22- -—=— 22 se Heat and moisture (the conditions of vegetable growth) greater to- wards the equator)... 22) 2s So oe ee ee ee Heat-capacity, effect of, on the temperature of soils__.__--------- Heat demonstrated by Count Rumford to be a form of motion -__. Heat given out by the precipitation of rain, very considerable_-__ ‘Heat-lichting,” explanation Of-2 -s-. Joo ee oe Heat, non-luminous, less penetrating than luminous heat -__- ---- Heat of the earth, original, numerous indications of -----_. --___. Heat retention of different kinds of earth, table of _--_-. ----_.__-_ Heat, the mechanieal equivalent of, accurately determined by Joule Heat, total diurnal, from the sun in summer greater at the pole than at the equator i223. e oo Be ee Height of clouds estimated by depression of the dew-point -_--_._ Herschel, Sir John, experiment by, on accumulation of solar heat in enclosed bO® : UP! eas pS } Rae SS = SS et > SS) ec. , Ds > ys: MLD Fhe ») pee 2 pS > Banaue BD? ) De : DP?222 F FWD 2 LVS, 3p DD» 2 Sy 2S yy) eo 3) BP. >> p>») 3 9088 01421 oe ih