800 



ON TAKING DAGUERREOTYPES WITHOUT A CAMERA. 



[1855 



the aurial wave formed by the vibration of the sonorous body ; 

 so the vibrations, more or less rapid or more or less vigorous, 

 of the electric fluid excited by the action of batteries of a 

 greater or smaller number of plates, are propagated in con- 

 ductors with the same velocity. Every one will see how the 

 hypothesis imagined by us to give a reason for natural pheno- 

 mena, will serve to suggest certain experimental investigations, 

 the results of which will test their validity or insufficiency." 



Melloni then says, that he shall shortly have occasion to 

 publish facts which clearly demonstrate the errors of certain 

 conclusions admitted up to the present time respecting electro- 

 static induction; and I am aware, from written communications 

 with him, that he considered the results arrived at by Coulomb, 

 Poisson, and others since their time, as not accordant with the 

 truth of nature.* In the meantime he died, and whether his 

 researches are sufficiently perfected for publication or not, I do 

 not know. 



The uniformity in the time and appearance of currents of 

 different intensities at the further end of the same wire in the 

 same inductive state, is a very beautiful result. It might at 

 first be supposed to be in opposition to the views I set forth 

 some years ago on induction and conduction, and the state- 

 ments more recently made with regard to time. That, however, 

 does not appear to :i.e to be the case, as a few further observa- 

 tions on Mr. Clark's recent experiments will perhaps show. 

 When the smaller battery is used, much less electricity passes 

 into the wire in a given time, than when the larger one is 

 employed. Suppose that the batteries are so different that the 

 quantities are as 1 to 10 ; then, ttiough a pulse from each 

 would take the same time for transmission through the wire, 

 still it is evident that the wire would be a tenfold better con- 

 ductor for the weak current than for the strong one ; or in 

 other words, that a wire having Only one-tenth of the mass of 

 that used for the greater current should be employed for the 

 smaller one, if the resistance for equal quantities of electricity 

 having dilferent intensities is to be rendered equal. 



My views connect the retardation of the transmitted current 

 with the momentary induction set up laterally by the insulated 

 and externally coated wire. The induction will be proportion- 

 ate to the intensity, and therefore its especial effect on the time 

 of retardation proportionately diminished with the less intense 

 current, — a result of action which will aid in rendering the 

 time of retardation of the two currents equal. 



The difference of time in the former experiments with air 

 wires, and earth or water wires, very clearly depends upon the 

 difference of lateral induction ; the air wire presented a retar- 

 dation scarcely sensible, the earth wire one amounting to nearly 

 two seconds. If the insulating layer of gutta percha could be 

 reduced from 0-1 to 0-01 of an inch in thickness, and mercury 

 could be placed on the outside of that instead of water or earth, 

 I do not doubt that the time wou.ld be still more increased. 

 Yet there is every probability that in any one of these vai-ying 

 cases, electric currents of high and of low intensity would 



* Hesays, " Ideceive myself much, or else the fundamentaltheorem 

 of electrical induction, as we find it ordinarily announced, ought to be 

 modified so as not to confound two efiFects completely distinct — the 

 electric state during induction, and after the contact and separation of 

 the inducing body. We know perfectly what occurs in the latter case, 

 but not in the former," &c. Again, " In my last letter I raised doubts 

 with regard to the consequences which have up to the present been 

 deduced from the experiments serving as a base for the fundamental 

 theorem of electro-static induction. These doubts have passed to a 



state of certitude in my mind and behold me at 



this time thoroughly convinced that the enunciation of that theorem 

 ought to be essentially modified." (July, 1854.) 



appear at the end of the same long wire after equal intervals 

 of time. 



Mr Clark's results may be stated thus : — A given quantity 

 of electricity at a high intensity, or a smaller quantity at a 

 proportionally lower intensity, will appear at the further end of 

 the same wire after the lapse of the same period of time. My 

 statement assumed the discharge of the same quantity at dif- 

 ferent intensities through the same tvire, and the quantities in 

 the illustrative experiments were measured by a Leyden jar. 

 In the consideration and further development of these results, 

 it must be remembered that it is not the difference either in 

 time, velocity, or transmission of a continuous current which 

 constitutes the object in view; for that is the same both for an 

 air wire and a subterraneous wire, but it is the difference in 

 the first appearance only of the same current when wires under 

 these different conditions are employed. After the first appear- 

 ance both wires are alike in power unto the end of the current, 

 and then a difference again appears which is complementary 

 to the first. 



There are many variations of these experiments which one 

 would wish to make, if possible, and perhaps by degrees the 

 possibility, or else equivalent experiments in other forms, may 

 occur. If the wire employed were changed from a cylinder to 

 a flat ribbon of equal weight, or to several small wires, all 

 being equally coated with gutta percha and submerged, differ- 

 ences would probably arise in the time of delay with the same 

 current ; and I think that the ribbon, presenting more induc- 

 tion surface than the cylinder, would cause more delay ; but 

 probably any of these, or of like varieties, would cause the 

 same delay for currents of different intensities. Again, one 

 can scarcely doubt that with different conducting substances, 

 as iron and copper, the delay would vary, as is the case in the 

 transmission of sound and light. That the delay for currents 

 of high and low intensity should be the same for the .same 

 wire in any one of such cases may still be expected, but it 

 would be very interesting to know what would be the fact. 



The prosecution of these results and the principles concerned 

 in them, through the various forms they may assume by such 

 like variations of the conductors and also of the currents, 

 offers, as Melloni has observed, most extensive and interesting 

 inquiries; even the power of a current to induce a current in 

 neighboring wires and conductors is involved in the inquiry, 

 and also the phenomena and principles of magneto-electric 

 induction. 



On taking Daguerreotypes without a Camera. 



BY J. r. MASCHER.* 



The accompanying stereoscopic pictures were taken by me, 

 by means of a box (to be described hereafter) that contained 

 neither lenses, reflectors, or in short any refracting or reflecting 

 medium of any kind. I accidentally made the discovery that 

 photographic pictures could be taken in this manner while 

 prosecuting some experiments relative to stereoscopic angles. 



It is well known that two pictures taken with two ordinary 

 cameras placed only 2i inches apart horizontally, will not when 

 placed in the stereoscope show proper or sufficient stereoscopic 

 relief, yet it is well known that the human eyes areonly placed 2* 

 inches apart, yet are enabled to see solid objects in their proper 

 solidity and relief; and to explain the why and wherefore of 

 these facts has challenged the attention of Professor Wheat- 



* Journal of the Franklin Institute. 



