Thermomelric Scales. 3S;> 



THERMOMETRIC SCALES. 



To Mr. Tilloch. 



Sir, — Referring to the note at the end of Mrs. Ibbetson*s 

 paper in your last number, J beg leave to observe that, not having 

 immediate access to the work referred to in her preceding com- 

 munication, I pointed out the error in the reduction of the de- 

 gree of heat shown by the plant in Mons. Hubert's experiment, 

 page 1S4, under the impression that Reaumur's thermometer 

 was correctly quoted. 



It nr)vv appearing that the circumstance is detailed with re- 

 ference to Celsius's thermometer, it must be obvious that instead 

 of making "the assertion respecting the heat the more impossi- 

 ble to be believed," it tends to strengthen it, by reducing the 

 extent of the variation : at the same time that it shows an in- 

 crease of temperature very evident to the sense of feeling, it 

 brings the phaeuomenoii more within the limits of probability. 



In both Reaumur and Celsius's thermometers the zero is fixed 

 at the freezing point of water, the range between that and boil- 

 ing being SO" in the former, and 100" in the latter. 



In my last* I pointed out that, according to the quotation in 

 page IS'l, the degrees of heat shown by the standard thermo- 

 meter and plant v.ere 



— ^ \-62.z= 72| F. ana — h 32 = 99| F., showing a 



rise of 27' F. Now as the degrees of Reaumur and Celsius 

 bear a relation to each other of 4 to 5, the difference will be 



~--\- 32 = 64-1^ F. standard thermometer: '"'^ ^ "" ^ +32 = 



^^ F. heat of the plant: the increase of temperature being 21|-^ 

 F. which is still very considerable^ and fully sufficient to pro- 

 duce the effect described. 



I should apologize for intruding upon your time at such 

 length on the present subject; but having in the former case 

 jjointed out what I considered an inadvertent error, I feel it in 

 some degree incum.bent upon me to notice that, although ad- 

 mitted, it has not been rectified. 



I have the honour to be. 



Your most obedient humble servant. 

 Thistle Grovp, Old Brompton, P. J. Brown. 



N'ov.4, lUlO. 



* Mrs. !l)bctso!i's notice of tlie error nlluderi to ImvitiL' rcnclicd us be- 

 fore Mr. IJiown's, wo ju(lf;i;il It iiiiiicec-Miiv ttu-n to insert tlio latter, as 

 the tlicinioinotrr referred to ^noved to be adilVercnt one from that wluctJ 

 lie noticed. Ilia ])rebent couimunication embraces both. — Ecrr. 



Vol. 48. No. 223. Nov. 1816. B b mines 



