Dr Brewster on the Mean Temperature of the Equator. 117 



a state of weakness that I could do hardly any thing more dur- 

 ing the season. In the short interval of fair weather which 

 now and then occurred in the course of the winter, I crawled 

 to the woods in search of mosses, but my limited knowledge 

 on that head does not allow me to say what they are. As 

 nothing could be effected in the way of botany, I began 

 forming a collection of birds ; but here I experienced a sad 

 hindrance from the state of my eyes, which, always weak, have 

 lately been much impaired ; and though I have felt no pain 

 or inflammation, yet they have become so dim that I can 

 hardly use the gun, which I could formerly do with consider- 

 able advantage. However, I am in possession of a species of 

 Pinus, the finest of the genus, and hope soon to obtain better 

 specimens, and plenty of ripe seeds. This is unquestionably 

 the most splendid specimen of transatlantic vegetation. I 

 have another species of Mimulus, M. alba. I left the ocean 

 in the middle of this month, but though I could have crossed 

 the continent and returned to England, I thought it incom- 

 patible with the interest of the Society which employs me, to 

 neglect so interesting a field of discovery as that now before 

 me, in the upper country towards the head waters of the 

 river. Excuse this bad writing. I have little time, and less 

 convenience for writing, my specimen board being the only 

 substitute for desk and table ; but then it contains some most 

 interesting plants under it. 



Art. XV. — Notice respecting the Mean Temperature of the 

 Equator. By David Brewster, LL. D. F. R. S. Lond. 

 and Sec. R. S. Edin. 



In the seventh Number of this Journal, (p. 180.) we laid be- 

 fore our readers an abstract of the results obtained by Mr 

 Atkinson, respecting the mean temperature of the equator. 

 According to these results, which were deduced from the Ame- 

 rican observations given by Humboldt, the mean temperature 

 of the equator at the level of the sea is §6°.55 of Fahrenheit, 

 while Humboldt himself made it only 81°.5. 



As the equatorial temperature must always be a fundamental 



