XII. A Description of an Improved Thermometer. Com- 

 municated by Daniel Rutherford, M. D. F. R. S. Edin. 

 ProfeJJbr of Medicine and Botany in the Univerfity of Edin- 

 burgh. 



{Read April $. 1790.] 



HT^HE following improvement on the conftruclion of the 

 X thermometer, by which it is fitted to mark the loweft or 

 the higheft point to which the fluid has attained in the abfence 

 of the obferver, is due to John Rutherford, M. D. of Middle 

 Balilifli. This gentleman communicated it to me fome time 

 ago, and accompanied the defcription with one of his thermo- 

 meters. The contrivance is fo very fimple and. ingenious, that 

 it well deferves to be made public. I therefore, by permiffion 

 of the author, beg leave to lay an account of it before the 

 Royal Society. 



1. If it be required, that the thermometer fhould mark the 

 loweft point to which the liquid has defcended within any given 

 time, a common fpirit of wine thermometer mud be provided, 

 of a convenient fize, fuch as is reprefented by the figure AB*. 

 Into the tube is introduced a fmall conical piece of coloured 

 glafs or enamel, (C), with its point turned towards the bulb of 

 the thermometer. This piece is about ^ inch long, and of fuch 

 diameter at the bafe, that it may move freely within the tube, 



yet 



* See the figure, plate 4. at the end of No. XIII. 



