242 



ELECTRICITY. 



photographs can be taken with any power given by 

 sunlight, but also that the exaggeration of light and 

 shadow, which has prevented the electric light from 

 being generally adopted as a source of illumination 

 iu the preparation of ordinary photographs of the 

 natural size or less, proved ot infinite advantage in 

 the reproduction of feeble, microscopical images of 

 highly-magnified objects. 



The microscopical pictures are clearer and more de- 

 fined than those produced by sunlight. The electric 

 light is much more manageable than sunlight, and 

 readily arranged to produce negatives with shorter 

 exposures. The magnesium light, though sharing 

 these qualities, is found to be less adapted to the 

 higher powers. 



The electric light is considered to be the best. 

 Grove's battery, already spoken of, is placed in a 

 closet just outside the operating-room. The battery 

 used by the doctor is the compact form of the 

 Grove's battery employed by Prof. Tyndall in his 

 celebrated lectures on heat and sound. It was made, 

 we understand, by Mr. Ladd, of London, who manu- 

 factures the apparatus used by Prof. Tyndall. 



The chief point about this battery is its compact- 

 ness. It occupies, when set up, a space of a little 

 more than two feet square, and the cells are so small 

 that a little over seven pounds of nitric and three of 

 sulphuric acid, costing altogether much less than one 

 dollar, is sufficient to charge the fifty elements and 

 run the battery for a day's work. The wires from 

 the battery are connected with the Duboscq lamp, 

 which is the one that was exhibited by that ingenious 

 maker at the recent Universal Exposition in Paris. 

 This lamp is provided with a clock-work, regulated 

 by a magnet, and keeps the carbon-points perfectly 

 steady. The light from the burning carbon-points, 

 which approximates in brilliancy the brightness of 

 the sun, is concentrated by a pair of condensing 

 lenses on the achromatic condenser of the micro- 

 scope, passes thus through the object and the object- 

 glass of the microscope, and projects the image on 

 the sensitive plate, which is placed at a few feet dis- 

 tance. The photograph is then taken by precisely 

 the same chemical process by which portraits are 

 photographed. 



This lamp maybe substituted for the electric clock 

 and battery in the above process with similar results, 

 but requires somewhat longer exposures. It is not 

 so well adapted to taking pictures with high powers, 

 and at the present price of the magnesium ribbon, 

 which is two dollars and one-half per ounce, is more 

 costly than the electric light. 



We are inclined to believe that the above new ap- 

 plications of the electric and magnesium lights will 

 prove of great practical value, by enabling micro- 

 scopists, laboring in the various branches of medical 

 and scientific research, to reproduce the results of 

 their investigations in such form as to make them in- 

 structive to the world. 



Dr. Woodward showed us during a recent visit 

 photographs of sections of cancers, tumors, and other 

 morbid tissues, in which the most minute structural 

 points were faithfully reproduced, with powers ran- 

 ging from 350 to 1,000 diameters ; and also of a great 

 variety of test-objects, some of which were magni- 

 fied as highly as 2,500 diameters. We can readily 

 understand how by the exchange of such pictures 

 microscopists, working at distant points, could co- 

 operate and assist in each other's labors. And we 

 are therefore glad to learn that it is probable that 

 the surgeon-general will publish at an early day a 

 ill account of those experiments, which will render 

 the process available for any microscopist of ordi- 

 nary industry. It is not necessary for the micro- 

 Bcopist to be a practical photographer, as any ordi- 

 nary portrait photographer can be employed by him 

 for the purpose. 



We understand that the magnesium and electric 

 lights have both been used for copying maps and 

 drawings, and no doubt much can be done to render 



this application more economical and simple than 

 hitherto. But it is not likely that these lights will 

 be generally introduced as sources of illumination in 

 taking ordinary photographs, for which they are un- 

 fitted by the violence of the contrasts of the light 

 and shade which they produce. 



Vegetable Electro-motors. Mr. Edwin Smith 

 contributes to the London Chemical News the 

 results of experiments to determine the electric 

 relations between vegetable substances of a 

 nature to act chemically on each other an 

 alkaloid and an organic acid, for example. He 

 deemed it probable that, whenever two flavors 

 are habitually conjoined in eating, the reason 

 why they mutually improve each other is be- 

 cause a certain amount of electric action is set 

 up between the substances employed to pro- 

 duce them, and that the rationale of the right 

 blending of flavors might be found partly in 

 galvanism as well as in chemistry. He says : 



Pursuing this idea, I tried pairs of eatables which 

 generally go together, such as pepper and salt, coffee 

 and sugar, almonds and raisins, and the like, and 

 found that a voltaic current more or less strong was 

 excited in every instance which I tested. Bitters 

 and sweets, pungents and salts, or bitters and acids, 

 generally appear to furnish true voltaic couples, 

 doubtless in consequence of the mutual action or 

 some alkaloid salt and an acid or its equivalent. As 

 others may like to repeat or extend the experiments, 

 I will describe shortly my^ mode of procedure : Cut 

 two pieces of platinum-foil about five inches by two 

 and a half inches, and a number of pieces of filter- 

 paper a trifle larger. Well- washed linen is sometimes 

 more convenient than filter-paper. Have a small 

 wooden board near the mercury-cups of the galva- 

 nometer, and let a short copper or platinum wire, dip- 

 ping into one of the cups, rest on the board. The 

 substances to be tried must be brought to a state of 

 solution, the stronger the better, by infusion, decoc- ^ 

 tion, or otherwise. Suppose coffee and sugar are to * 

 be operated upon : solutions of both having been 

 prepared, dip into each a slip of filter-paper ; place 

 one slip on one of the pieces of platinum-foil, and 

 the other on the second piece. Next lay the first 

 slip and its foil on the board, with the metal touching 

 the copper wire before mentioned. Lay the second 

 slip with its platinum upward, so that the coffee and 

 sugar come into even contact with slight pressure, 

 and immediately connect this upper slip, through a 

 bit of copper wire, insulated from the touch, with the 

 other terminal of the galvanometer. Deflection oc- 

 curs instantaneously, and may be increased to a con- 

 siderable vibration by breaking and making circuit 

 at the right swing of the needle. After a few distinct 

 vibrations, it is well to turn over the whole pile of 

 slips just as they are, and connect opposite ends with 

 the galvanometer, so as to reverse the current. This 

 is desirable for the sake of confirming your previous 

 observation, and of correcting any slight disturbing 

 cause arising from the wire and mercury-connectors, 

 temperature of the hand, etc. It will be found that 

 coffee and sugar have the same electrical relation to 

 each other as zinc and platinum. Coffee, in fact, 

 is the positive, sugar the negative element. ^ I sub- 

 join a table of the results of numerous experiments, 

 conducted in the manner above described. 



ELKCTRO-POSITIVK. ELECTRO-NEGATIVE. 



Coffee Sugar (loaf). 



Tea (black) 



Cocoa. 



Nutmeg. 



Cloves 



Cinnamon 



Mace 



Vanilla 



Almonds 



