?4$() ACCOl/Nt OF THERMoM£T£*S. 



Six's thcrrao- Contrivances acceptable. Mr. James Six communicated, 

 about 25 years ago, to the Royal Society a thermometer, in 

 which two (mall indicating pieces were driven by the fluid in 

 the tubes to (rations where they ftuck, and remained after the 

 change of temperature, and (hewed the higheft and loweft 

 degrees that had occurred fince the laft placing of them in 

 contact with if. As this inftrument is fufficiently known, and 

 I am now to advert to a fimpler contrivance, I will difmifs 

 that fubjeft and advert to this laft. 

 ©bjc^ions to it. In Mr. Six's complicated thermometer the tubes were ver- 

 tical, and the indexes (luck in the glafs by their fpring ; be- 

 tides which, a fmall piece of fteel wire being expofed to alco- 

 Another ther- hoi, was at length oxided and fet raft. The other contrivance 

 ihews the Treat- novv *° ^ e ^ een m a " our London fliops, and refpeciing which 

 t<k and Jeaft you will do an acceptable fervice to your readers and the 

 temperatures, fcienilfic world, by inferting a tketch in your Journal, con (ills 

 fimply in two thermometers, one mercurial and the other of 

 alcohol (Fig. I, PL X.) having their ftems horizontal; and 

 the former has for its index a fmall bit of magnetical fteel wire, 

 and the latter a minute thread of glafs, having its two ends 

 formed into fmall knobs by fuiion in the flame of a candle. 

 Defcription. It The magnetical bit of wire lies in the vacant fpace of the 

 ,. as ameicuml mercurial thermometer, and is pufhed forward by the mercury 



thermometer ' * *. % ] J 



which ihews the whenever the temperature rifes and pufhes that fluid againftit: 



m J ximu ^'' and but when the temperature falls and the fluid retires, this index 

 meter for the is left behind, and confequentjy thews the maximum. The 

 minimum. other index, or bit of glafs, lies in the tube of the fpirit ther- 



mometer immerfed in the alcohol, and when the fpirit retires 

 by depreflion of temperature, the index is carried along with 

 it in apparent contact with its interior furface : but on increafe 

 of temperature the fpirit goes forward and leaves the index, 

 which therefore ihews the minimum of temperature fince it 

 was (ei. As thefe indexes merely lie in the tubes, their rc- 

 frftance to motion is altogether inconfiderable. The fteel in- 

 dex is brought to the mercury by applying a magnet on the 

 outfide of the tube, and the other is duly placed at the end of 

 the column of alcohol by inclining the whole inftrument. 

 Quertion. Why I beg you will explain the motion of the glafs index. I can 

 ir^dex^wa 8 ^ 5 ea ^'^ underftanci * rom lne general facl that mercury repels pel, 

 mains in the that this fluid will drive the fteel index before it ; but I cannot 

 *«* make 



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