230 



THE "MASTODON GIGANTEUS." 



[1853. 



ed to a pair of electrodes, in tlie solution forraei-ly described as 

 being generally recoinmended. Each electrode had live square 

 inches of f.ue, an 1 was oated on the back to prevent radiaiion. 

 They were phiced one inch apart, and had thin plates of wood 

 bound against their elgvs, to prevent any lateral spread of tlio 

 current iu pasjiug between them. Tlie following was then ob- 

 tiiined : 



Battery plates in contact gave 300 cubic inches gas per hour. 



Electriitles iu contact do. 216 do do. do. 



Current through electrolyte, at 58°, gave IG cubic in. gas perh. 23'I5 

 do. do. 6J° do. 2.) do. do. 18-15 



do. do. ]00° do. 27 do. do. 13 00 



do. do. 175° do. 37 do. do. 8-96 



The last column of figures shows the value of the resistance 

 of the solution, its compared with B of the formula. This col- 

 umn was obtained by first uniting the battery plates, and after- 

 ■wards the electiodes. 



From the above table it ap])eai-s that beat may be made to di- 

 minish the resistance in the decomposition cell in the proportion 



■2 E 



of 2-5S to 1 : and the whole resistance by 2-25. And as-—— 



E 



R -f r ; therefore, by heating the electrol3'te, we may with a sin- 



2 

 gle electrical equivalent make a plate as rapidly as by working 

 at atmospheric temperatures with two batteries in consecutive 

 order, with double surfaces, (four times the battery and twice the 

 e.Kpense.) 



But as Smee's laws require that, in forming a plate, certain 

 mutual co.iditious of ajipaiatus be maintained, it follows that 

 alterations in one element or condition must be attended by cor- 

 responding changes in the others. Hence, if the temperature of 

 the electrolyte be raised to a certain point, and the apparatus 

 correspondingly adjusted, it is e\ident that, to avoid incessant 

 adjustment, the original temperature must be maintained. 



Thus, to avail ourselvesof the advantages experimentally found 

 from heating the solutions, an apparatus for steadily maintaining 

 a high temperature in the electrolyte through se\-eral successive 

 days becomes indepensable. 



As the electrotype operations are not suspended at night, it is 

 important that the heating apparatus should ]ierform its office 

 for at least twelve hours without supervision or replenishing its 

 fuel ; and its action should be sensibly uniform, during all the 

 time, between successive replenishings. 



Such an apparatus I have devised, aTid is now in use. A 

 peck of charcoal furnishes fuel for twelve hours, and maintains 

 100 gallons of copper solutions steadily, at any required point 

 between 100= and 200 = . 



With the above arrangement in use, I have made a large re- 

 verse or alto, ami I'eturned the original to the engraving depart- 

 ment in 55 hours from its bein^r placed in my hands. This time 

 included trimming the edges and the preparations to prevent ad- 

 hesion. 



Again recun-ing to Ohm's formula, the relative value of R to 

 r w;is once more experimentally found. This gave R:)-:: 1 :4 



or Q =r-v77=0'20, a great improvement as compared with the 

 first determination of R: r :: 1: 19, or Q= j _[.^,j ^0-0.5. Hav- 

 ing now made r so small compare:! with R, the size of the bat- 

 tery can be profitably increased until the result is about 24. 

 Moreover, using a double arrangement of cells with the double 



surfaces, for a double effect, we now have 2 I — r- B^.tXI^'^''^'^ ' 

 As the relative resistance of the electrolyte becomes now still 



smaller, we may yet more increase the battery surface, until the 

 result is nearly O-o. 



The electrotype has now ceased to be a mere experiment, un- 1 

 certain, expensive, and slow. I have lately formed plates of II 

 most excellent quality, at the rate of three pounds to the square 

 foot, in 24 hours. This rate will lequii-e but two days to form 

 one of our largest plates, basing ten square feet surface, and one- 

 eighth of an i ich thick. 



Actions in the electrolytic solution. — The quality of the de- 

 posited metal is governed solely by the relations between the 

 quantity of the electricity passing through an}' solution and the 

 amount of metal the solution contains. The usual supposition is, 

 that the acid of the salt goes to one electrode and the metal to the 

 other, but it is now ascertained that no such mutual transfer takes 

 place; for, while the acid is carried to tlie positive electrode, the 

 metal is not carried to the negative electrode. Hence, however 

 strong the solution on commencing the process, the negative elec- 

 trode, by abstracting the metal in its vicinity, is soon surrounded 

 with a weak solution. With a simple wire electrode, the ex- 

 hausted solution surrounding the electrode is readily renewed by 

 mere difference of si)ecific gravit)' producing a flow. But, with 

 large parallel plate electrodes, this rapid renewal of dense solu- 

 tion becomes impossible, and the electiode is soon surrounded 

 with a weak solution. This state of things must be recognized 

 in adjusting our b;ittery arrangements. Electrotvpists not aware 

 of this fact find themselves much perjilexed by fiuling to accom- 

 plish with large plates what is so easily done with medals or 

 small plates. 



It would, at first sight, appear that, by strengthening the solu- 

 tion of sulphate of copiper, a more rapid supply of metal to the 

 electrode would be obtained. Unfortunately, the eft'eet of this is 

 to diminish the solvent capacity of the water in the solution for 

 the sulphate formed on the positive electrode by the action of the 

 transferred acid. The grand essential in electrolysis i'- liquii.lity. 

 Thus, if the quantity of free water surrounding tlie positive elec- 

 trode be small, this electiode is soon enveloped in a saturated 

 solution, and the newly-formed salt remains undissolved upon it. 

 This salt, being a non-conductor, virtually excludes the electrode 

 from the solution, and thus arrests the current, except wdien the 

 efflux of saturated solution permits the salt to dissobe, and so re- 

 opens the pas.sage for the eurrentin irregular quantities. From 

 this spasmodic action result plates of copper-sand, or sometimes 

 copper as soft as lead. 



By applying heat to the solution when this state of things exists, 

 the solvent capacity of the water for the salt is increased, rapid 

 diffusion takes place, the salt is carried to the negative electrode, 

 and the exhausted water to the positixe electrode ; the dormant 

 batteries rush into uninterrupted action, and in a short time a 

 plate is deposited, having all the hardness and ela-iticity of ham- 

 mered or rolled copper. Smee's conditions, then, seem to m.ain- 

 tain themselves. The electrotypist's axiom of " work slowl_v," 

 requires to be reversed into "the quicker the work, the better the 

 quality." 



Notice of the "Mastodon Gigant.us" of Dr. J. C. Warren.* 



We have already breifly announced the publication of the 

 magnilicent volume on the " Mastodon Gig inteus," by the emi- 

 nent surgeon and scholar, Dr. Warren. Turning aside from the 

 profession which he has honored by his profound knowledge and 

 successful labors, he here entei's the 3>-ena of Science, and substan- 

 tiates his claims to a distinguished place among the Zoologists of 

 the age. 



•Dcscrlpiirri ol a Skek-ion ol the MasUidon GmaiiUMis ol' Nonh America, 

 bv John C. Warren, M.D., &c. 219 pp -llo.' wilh a fronlispiece and 27 

 plnlesin4lo. Boston: IS.'>2. .T. Wilson A: Son, 22School Street.— SiV/Jaur. 



