1854.] OBSERVATIONS ON THERMOMETERS. 125 



watched. From these registries it is evident that the 

 freezing-point does not confine its further retrogression, 

 and that, after contracting to 41, or below, it will still 

 indicate a motion above or below 41, or, in other terms, 

 is not solidly congealed. These observations, noticed in 

 the Appendix, as compared with the action of the spirit 

 thermometers, may afford interesting matter for those 

 inclined to pursue this subject. 



Notwithstanding this peculiar disposition of the mer- 

 curial thermometers, it cannot but prove a source of 

 great satisfaction to those who have bestowed so much 

 pains on these delicate instruments to learn that, under 

 all changes, both spirit and mercury have been found so 

 closely to coincide. 



Another fact, entirely incomprehensible to me, occurs 

 with regard to thermometers used for water purposes, 

 either in the sea or in the wet and dry bulb thermo- 

 meters ; these, although agreeing perfectly before sub- 

 jection to moisture, disagree completely for many days 

 after depriving them of their covering, or completely dry- 

 ing them. A pair of the most perfect, now before me 

 (belonging to the wet and dry bulb), undergoing clean- 

 ing preparatory to fresh clothing, have for three days 

 afforded two degrees of difference ! and yet for weeks, 

 during the winter of 1852-53, they coincided at every 

 division ! 



March 4. I have not progressed towards recovery as 

 I had anticipated ; in fact, I learn that this is not a climate 

 to trifle with. Undue exertion of the lungs (reading the 

 service on Sunday) has thrown me back and confined me 

 to cabin exercise. The following ideas have lately been 



