J24< EI,ECTRICAL MACHINE. 



oF the Royal College of Phyficians, to ufe a little rancid fat 

 or oil, in order lo facilitate my labour and favour my indolence, 

 and I was agreeably furprifed at ray fuccefs. The College 

 order the pureft and fweeteft fat to be ufed; neverthelefs the 

 utmoil diligence and care in rubbing the mercury with it does 

 wot produce fuch an accurate combination at firft as is accom- 

 pli (hed, after being fet by for a week or two, and this my be 

 made evident by comparing two fpecimens of ointment made 

 . with equal care and diligence, the one being quite recently 

 finilhed, and the other having afterwards been kept undifturbed 

 for two or three weeks. — I merely offer thefe hints for the con- 

 (ideration of wifer heads than mine, and fliould they with this 

 view be honoured with a place in your valuable repofitory, 

 your ijidulgence will be moll refpeflfully acknowledged by 



Sir, 



Yours, &c, 



NORTHUMBRIENSJS. 



VIII. 



JmproT^mcnt of the EliciricalMaddnef chiejfj/mih refpe6t to ijie 

 Rubbers; by Mr, Wolff, of Hanover'^, 



Pefcription of xVlY ele6lrical apparatus is a plate machine, conflruded on 

 Uic machine. ^j^g pj^j^ ^^f ^j^^t defcribcd by Van-Matum f, with a few flight 

 The plate. alterations, which are principally in the rubbers. The plate 



is eighteen inches in diameter, and the piece of wood, which 

 receives the fcrew that faflens the plate to the axis, is an inch 

 and half in diameter. The rubbers (at the extremities of 

 which, toward the axis, are flicks of black fealing-wax, 

 rounded at each end, and overhanging or projefting on three 

 fides) are in conta61 with the glafs for the length of 5f inches, 

 Confequently the diliance from the circular or central piece 

 of wood to the rubbers is 2j inches, to which extent the plate 



♦ From GilbeiVs Anrahn der Phy/ichy 1802, No. 13. p; 601. 

 f Obfern;ationi fur la Phy/ique, Vol. 38, p. 437, or PhilofophicaJ 

 Journal, 4to. Series, No. 2. 



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