78 Royal Society. 
diation is not less important, and has, in particular, beert 
very clearly established by some very excellent experiments 
by Mr. Leslie on the celerity of cooling im vesselss which 
radiate caloric unequally; water, for example, cooling more 
quickly jna tin vessel coated with lamp-black than when 
clean, the coating, though diminishing the conducting 
power, more than compensating for this by inereaying the 
radiating power. 
“‘ The proportion between the two must be considerably 
dependent on the temperature at which the estimate is 
made; for at high temperatures the cooling by slow com- 
munication will be accelerated by the more rapid current 
formed in the surrounding medivnY from the heated sur- 
‘face, while this can have no effect on the radiation. Mr. 
Leshie conciudes from his experiments, that at low tempe- 
ratures the heat lost by the direct communication is someé- 
what less, and at higher temperatures considerably greater 
than what is lost by radiation. 
«© The influence of these circumstances on refrigeration 
pives rise to sume results rather singular, and to some prac- 
tcal applicatrons of considerable importance. Thus water 
cools more quickly in a metallic vessel, the outside of which 
ys blackened, coated with varnish; or even covered with 
linen,-than when clean and polished. Hence, im conduct- 
ing the process of artificial refrigeration, vessels with such 
coatings will allow it to be performed most quickly ; for the 
same reason, where the object is to condense vapour or 
steam, as, for example, im applying this condensation to 
procure heat, the external surface of the tubes through which 
the steam passes ought to be painted or blackened; while, 
if it is of importance to prevent as much as possible the 
condensation, as in conveying steam, or applying its élasti- 
city as a mechanical power, the external surface ought te 
be clean and bright.” 
XV. Proceedings of Learned Societies. 
ROYAL SOCIETY. 
Dies Society assembled, after the holidays, on the loth; 
and concluded the reading of Dr. Parry’s paper on the 
means of curing certain nervous affections merely by pres- 
sure on the carotid’ artery ; a method which he proposed 
geveral years ago, and has found effectual in almost every 
case. 
The same evening a mathematical paper on the hyper- 
bola, 
