174 
Considering, first, the northern hemisphere alone, the constants 
are introduced into such a formula by a comparison of the observed 
temperatures of latitudes 0°, 30°, 50°, and 70°, with the following 
result : — 
T a = 12°-5 + 59°-2 cos.f X + 38°-l L' cos. 2x 
where T is the temperature of latitude X on Fahrenheit’s scale, 
and X/ the effective proportion of land in the circumference of that 
parallel. 
The extension of the formula to the southern hemisphere is 
shown to give satisfactory results, although all merely empirical for- 
mulae for the northern hemisphere altogether fail in this case. 
Some other and independent confirmations of the formula are 
then adduced. 
Supposing the globe to be entirely composed of land, or entirely 
of water, the temperature of any parallel may be deduced from the 
formula. In the case of a globe all land, the Equatorial tempera- 
ture would be about 110°, and the Polar temperature about — 26°; 
whereas, on an aqueous sphere, the formed would be about 72°, and 
the latter + 12°. 
2. On the Spermogones and Pycnides of Lichens. By W. 
Lauder Lindsay, M.D., F.L.S. Communicated by Prof. 
J. IT. Balfour. 
The researches contained in the author’s memoir, of which the 
following is a brief abstract, extended over a period of several years, 
and are based on careful microscopic examination of several thou- 
sand specimens of lichens from every part of the known w r orld. 
The author examined the lichens of the Hookerian Herbarium at 
Kew, which contains an unrivalled series of specimens collected by 
the various surveying and exploring expeditions of the British Go- 
vernment, as well as by all the more distinguished modern British 
travellers. This collection is further valuable, from containing authen- 
tic specimens collected and named by Borrer, Turner, Hooker, Bro«* 
die, Carmichael, Babington, and other distinguished British lichenolo- 
gists, as well as by Acharius, Schaerer, Swartz, and other continen- 
tal authors. Access was also had to the Menziesian Herbarium in 
the University of Edinburgh, the Herbaria of the said University, 
of the Botanical Society of Edinburgh, of the Museum of Irish 
