538 



generally assumed in medical works on climate, but rather on 

 the combined effect of it taken in conjunction with moisture, 

 with currents of au', mth radiation, and with variations of the 

 densities of air, must be manifest even from a theoretical con- 

 sideration of the subject ; but up to the present time this com- 

 bined eflfect does not appear ever to have been experimentally 

 investigated. It occurred to me that, by substituting for the 

 human body a thermometer heated to its temperatiu-e, the time 

 in which it cooled down in any locality would afford a measure 

 of the cooling power of all those agencies combined in that 

 locality. Accordingly, having heated the bulb of a thermo- 

 meter to 90°, that being the average heat of the surface of the 

 body, I observed the time it requii-ed in different situations to 

 cool down to 80°, when taken inversely, corresponded so well 

 with what my feelings told me of the cold of those situations, 

 that I made a variety of experiments which con^^nced me of 

 its truthfulness and value. 



" Having introduced a short account of it Into a paper 

 which I read at the medical section of the British Association, 

 when in DubUn in 1835, I proposed, in order to avoid cir- 

 cumlocutions, that the thermometer so apphed should be 

 called a Psychometer, or measurer of refrigeration (from 

 xpvxog). The members present at the meeting of the section 

 appeared to view the proposal with great interest. No objec- 

 tion was offered to it, and a resolution was passed appointing 

 committees in London, Dublin, and Edinburgh (to which 

 copies of my communication were to be furnished), -with a re- 

 quest that they should report to the meeting to be held in the 

 following year. 



" I have to plead guilty of a great omission and of appa- 

 rent disrespect towards the Association, in not availing myself 

 of the extensive opportunity thus promptly thrown open ; but, 

 not wishing to compromise my prospects as a practising phy- 

 sician, by ajDpearing before the public in the light of an ex- 



