May 26, 1893. J 



SCIENCE. 



293 



touched with loadstone seizes iron with not less force than load- 

 stone itself. These fights, seditions, conspiracies, in a stone, as 

 though it were nursing quarrels as an occasion for calling in 

 auxiliary forces, are the maunderings of a babbling hag, rather 

 than the devices of an accomplislied prestigiator." 



So much for his attacks on the older philosophy As an exam- 

 ple of his own reasoning, we may give the following: " What is 

 it that produces this movement? (speaking of the attraction of 

 electrified bodies). The body itself circumscribed by its contour? 

 Or is it something imperceptible for us, flowing out of the sub- 

 stance into the ambient air? And, if it is an effluvium, does the 

 effluvium set the air in current, and is the current then followed 

 by the bodies? Or is it the bodies themselves that are directly 

 drawn up? But, if the amber attracts the body itself, then 

 suppose the body itself is clean and free from adhesions, what 

 need is there of friction? Nor does the force come from the 

 lustre proceeding from the rubbed and polished electric, for the 

 vincentina, the diamond, and pure glass attract when they are 

 rough, but not so strongly nor so readily; because they are not 

 so readily cleaned from the extraneous moisture settled on the 

 surface, nor are they subjected all over to such an equal degree 

 of friction as to be resolved into effluvia. Nor does the sun, with 

 its shining and its rays, which are of vast importance in nature, 

 attract bodies thus, and yet the common run of philosophers think 

 that liquids are attracted by the sun, whereas only the denser 

 humors are resolved into rarer, (and) into vapor and air; and thus, 

 through the motion given them by diffusion, tbey ascend to the 

 upper regions, or, being attenuated exhalations, they are lifted 

 by the heavier air. Neither does it seem that the electric attrac- 

 tion is, by the effluvia, rarefying the air so that the bodies, im- 

 pelled by the denser air, move towards the source of rarefaction. 

 If that were so, then hot bodies and flaming bodies would attract 

 other bodies, but no lightest straw, no rotating pointer is drawn 

 toward a flame. If there is afflux and appulsion of air, how can 

 a minute diamond, the size of a chick-pea, pull to itself so much 



air as to sweep in a corpuscle of relatively considerable length, 

 the air being pulled toward the diamond only from round a small 

 part of one or other end ? Beside, the attracting body must move 

 more slowly or stand still before coming into contact, especially 

 if the attracting body be a broad flat piece of amber, on account 

 of the heaping-up of air on the surface, and its rebounding 

 after collision. And if the effluvia go out rare and return dense, 

 as with vapors, then the body would begin to move towards the 

 electric a little after the beginning of the application, yet when 

 rubbed electrics are suddenly applied to a versorium, instantly 

 the pointer turns, and the nearer it is to the electric, the quicker 

 is the attraction. ... In addition to the attraction of bodies, 

 electrics hold them for a considerable time, hence it is probable 

 that amber exhales something peculiar which attracts the bodies 

 themselves, and not the air. It plainly attracts the body itself 

 in the case of a spherical drop of water standing on a dry surface ; 

 for a piece of amber held at a suitable distance pulls towards 

 itself the nearest particles and draws them into a cone, were they 

 drawn by the air the whole drop would come toward the amber." 



Page 273. "The variation in the Indian Ocean all the way to 

 Goa and the Moluccas is noted by the Portuguese, but they are 

 mistaken in many points, for they follow the first observers who 

 set down the variations for sundry places, ascertained by the use 

 of unfit instruments, or by inaccurate observations, or by con- 

 jecture. Thus in the island of Brando they make the compass 

 vary 33 degrees to the northwest. Now, in no region, in no 

 place on the earth that has not a higher latitude than that, is the 

 variation so much as 23 degrees; in fact the variation on the 

 island is trifling, so when they say that in Mozambique the com- 

 pass varies to the northwest one point, they are in error, even 

 though the compass they use be that of Portugal, for without a 

 doubt the needle varies in Mozambique to the southwest one- 

 quarter of a point or more." 



The book is handsomely bound, and will form a valuable addi- 

 tion to the electrical library. r. ^ p 



ATonk 



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Descriptive pamphlet free. 

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Beware of Substitutes and Imitations. 



Exchanges. 



[Freeof charge to all, if of satisfactory character 

 Address N. D. C. Hodges, 874 Broadway, New York.l 



For sale or exchange.— Johnson's Universal Cyclo- 

 PEBdia, 8 vols., ed. 1888. Binding, half-morocco. 

 Will sell cheap for cash or would exchange for 

 typewriter. Address W. J. McKom, Mason, Mich. 



I have 500 microscopic slides to exchange in lots 

 to suit. Want Kodak, flrst-class field-glass or 

 scientiflc books. A. C. Gruhlke, Waterloo, Ind. 



Texas Plants. I will collect sets of plants repre- 

 sented in this region of Texas, either for sale or 

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For sale or exchange— A Telescope (36 diameters, 

 copper barrel;- for $20 cash or scientiflc books of 

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For sale— A complete set of the Reports of the 

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The undersigned has skins of Pennsylvania and 

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 specimens: which he wishes to exchange for ma- 

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 J. Percy Moore, School ot Biology, University of 

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for sale or exchange.— I have a Caligraph type- 

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 is in a heavy leather, plush-lined office case, the 

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 it, either by sale or exchange, anew, No. 5 "Kodak" 

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 price of what I desire in exchange is $78. Address, 

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For sale.— An Abbe binocular eye-piece for the 

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For sale or exchange. — One good long range Rem- 

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 water, and marine shells. Want shells. Safety, 

 camera or printing press. A. H. Boies, Hudson. 

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Wants. 



WANTED. — Second-hand copy of Ehrenberg's 

 Radiolaria, Berlin. 1875. Selected diatom 

 slides, cash or both in exchange. D. C. Lewis, M D 

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WANTED, as principal of a flourishing technical 

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WANTED.— A young man as assistant in our 

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THE undersigned desires specimens of North 

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 their pterylosis. These species are especially de- 

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 above are requested to communicate with Hubert 

 Lyman Clark, 3923 Fifth Avenue, Pittsburgh. Pa 



A COMPETENT TEACHER of botany in coUege 

 t\ or university is open to engagement. Address 

 L., Box 86, Rochester, Mich. 



CAN any one inform me as to the age to which 

 cats have lived? I have one twenty years old 

 Edward D. Webb, 1.32 W. Eighty-flrst St., New York. 



WANTED — Second-hand. Foster's Physiology, 

 Balfour's Comparative Embryology, Claus & 

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A GRADUATE ENGINEER will give instruction 

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