EU-nvometcr.—Sc'teni'ific Procefs of Tanning, 27I 



which they ftriie a pair of uninfulated metallic bars. In Plate XII. Fig. 3, A reprefents 

 the infulated metallic cap, from which, at C, depend the two narrow pointed flips of gold- 

 leaf. BB is the glafs (liade, which ferves to fupport the cap, and defend the leaves from the 

 motion of the furrounding air. DD are two flat radii of brafs, which open and fliut by 

 Rieans of one common axis, like a pair of compafles. By a contrivance of fprings, they are 

 difpofed to open when left at liberty ; but the micrometer fcixw E ferves to draw a nut, 

 which has two (leel bars, with a claw at the end of each, that enters into a correfpondent 

 flit, in two fmall cylindrical pieces, to which the radii are fi.Ked refpe£llvely. This appa- 

 ratus is feen in another pofition iu Fig. 4. KL reprefents a piece of brafs, which 

 ferves as the frame for the work, and fits the lower focket of the ele£lrometer, FF, 

 Fig- 3- In this the letters I H indicate the cylindrical pieces which carry the radii, and 

 are feen from beneath. On the fide of the nut G, one of the ftecl drawing pieces is feen ;. 

 the other being on the oppofite Cdc, and confequently not vifibk. Towards L appear the 

 two re-a£lion fprings. The other paits require no verbal defcrlption. 



In the common conftruClion of the gold-leaf eleclrometcr, there are two pieces of tinfoil 

 parted on oppofite parts of the internal furface of BB ; againd which the gold-leaf ftrikes 

 when its ele£lricity is at the maximum. If the radii DD be left at the greateft opening,, 

 our inflrument does not then difl^er from that in common ufe. But if the divergence pro- 

 duced by the conta£l of an atmofpheric conduiSlor, or any other fource of ele£lricity, be fo 

 fmall as to render it doubtful whether the leaves be eleftrified or not, the radii may then be 

 brought very gradually together by means of the fcrew, until the increafed divergency from 

 their attraftive force be fufficient to afcertain the kind of eleiSlricity poflefled by the leaves. 

 In this and all other cafes, the divifion on the micrometer head, which (lands oppofite the 

 fixed index, at the time the leaves ftrike the radii, will fliew the greater or lefs degree of 

 intenfity- 



X. 



The improved Procefs of Tanning. By Citizen SeGUIN *. 



XN confequence of our knowledge of the multiplied refearches and Important difcoveries 

 of Citizen Seguin rcfpe£ling aftringent fubflances, and the happy application of thofe dif- 

 coveries to Amplify and perfeft the art of tanning, we invited him to viCt the public la- 

 boratory, for the purpofe of communicating his proceffes and obfervations. Far different 

 from thofe felfilh manufaflurers, who carefully conceal under the cloak of pretended myf- 

 tcry, operations in themfelves fimple, frequently tranfmitted by oral tradition, and which 

 have coll them neither trouble nor expence, the Citi/.en Seguin did not hefitate to comply 

 with our wiftics, and has devoted to this obje£l two fittings, at which all the pupils, and 

 the grcatcfl part of the inftitutors and agents of the fchool, were prefent. He not only 

 cxhibitc<l without rcferve all that experience and meditation had difcovered to him, but he 

 likewife came attended by ikilful workmen, with proper inllruments to execute all the 

 proccfles. Laflly, he furniflied gratuitoufly the flcins, and a confider.ible quantity of tan, 



• Reported by Citizen Chaulfjcr ; being part of the Tr.infai\ions of the Polytechnic School of Fiance. From 

 tliiir Jouraal, IV. 678. 



