TRANSACTIONS OF THE SECTIONS. 
41 
nwter (which was communicated by Mr. Caldecott to Mr. Forbes for publication) 
hiipp^ in the Edinburgh Transactions. The principal results (mean of three 
tars) are contained in the following Table, from which it appears that the mean 
iaperatnre of the ground is nearly 0 ® higher than that of the air, and also that at 
wdre feet the range is still very considerable :— 
Air. 
Three Feet. 
Twelve Feet. 
0 
0 
0 
January ... 
78-9 
85-0 
85*5 
February ... 
80-4 
86-6 
85*8 
March . 
82-7 
88*8 
86*4 
.April . 
83-4 
89'C 
86*9 
May . 
81*6 
88-4 
June . 
79-9 
85-0 
86-9 
July. 
79-4 
83-2 
8C-5 
August . 
79-0 
83-6 
85-9 
September.. 
80-0 
84*6 
85-6 
October. 
79-1 
84*7 
85*7 
November.. 
79-7 
84-6 
85-7 
December... 
78-0 
84*2 
85-6 
80-0 
85*7 
86-0 
On the Cause of the Aurora, awl (he Declination of the NeedU'., 
/ly G. A. Rowell. 
Jtdmission that electricity is raised by evaporation, carried northward iri 
regions of the air, and then brought down by condensation, Mi% Rowell 
the existence of compensating under-curnnits of electricitj’ returning from the 
^impolar (positive) pari# of the earth’s surface to the tropical (negative parts}. 
® corrsnts he ascribes the direction of the magnetic needle 5 and to the inter- 
¥iuii of these currents, by the i’y and non-conducting state of the air m me 
51'“ r^ona during some parts (whereby the electricity is accumulated m the clouds 
It flishes back throogh the higher and rarer air towanl the more temperate re- 
Pjl.bereferstbe exhibition of aurora, and the coincident disturbances of the needle, 
^die same basis he endeavour# to explain the production and locality ot me 
Jgttic poles, which he supposes not to be subject to periodical displacement but 
nth in intensity and relative influence, according to physical conditio , 
M the openness of seas, geological changes, See. 
Cause of EvaporaHon, Emn, Hailstojies, and the Winds of temperate 
regions. JSy G. A. Rowell. 
I^fic explanation of ratn and cognate phenomena, the author 
•jj? by^thesrs. Electricity having no weight, and diffusing itself 
^of bodies, the minute particles of water, oven in their tn^^Gther 
■ o^coDipletely enveloped in the iiatur^ coating of electricity, ^ ^en- 
it npariy the space of an equal weight of air^ and ar . 
jj|*yy*nt 5 when by heat tlicir specific gravity is lessened, and P 
enlarged by the augmentaUen of surface, Uiey are uplifted in ’ 
particle becomes condensed, the electricity, bemg m , ^ 
and dew is deposited i or the particles, being above J ® 
isl vs’ **tch other and form clouds and tain. th® ° 
thus occasioned, the author ascribes many (especially 
»ind». and with this view refers to cases of extraordinary depths of fam 
‘S'‘'’'eiy short tiroes. 
