TL 
Correspondence—Mr. T. P. Barkas. 429 
perpetually radiating away. When this is brought into the reckoning, 
there is no such decrease in available energy as Mr. Greenwood’s 
argument supposes. The reason for expecting that the winter 
snowfall will be increased with increased eccentricity is that the 
heat-receipt during winter will be then diminished. Some vapour 
which the sun’s heat might have maintained as vapour during the 
winter, will then radiate off its heat without compensation ; will be 
chilled and fall as snow. But the summer’s receipt of heat is 
increased, increased to the exact extent of the winter decrease, and so 
to the extent required for the dissipation of the supposed additional 
snow. The heat thus spent in dissipating Mr. Greenwood’s extra 
foot of snow would before the increase of eccentricity have been 
spent in preventing that snow from being formed. There is no 
increase of work to be done. 
Mr. Greenwood’s argument would become correct if the snow 
were supposed to be generated in some different region, and thence 
brought to the region considered. Obviously a room will be chilled 
if a block of ice be introduced. 
I find it difficult to reconcile the language of Mr. Greenwood’s 
second paragraph with the article which it criticizes. He says that 
I argue from “increased radiation being greater in proportion to 
the increase of temperature.” He probably means, “ greater than in 
proportion.” He says that I ignore the fact that if radiation is 
increased in greater proportion by arise in temperature, it is decreased 
in like proportion by a fall. This fact is only roughly true, just as 
when a conical vessel contains water, it is true that whether the 
water level be raised or lowered an inch, the quantities to be poured 
in or poured out are nearly the same. But only roughly, not quite. 
The equality is not perfect. This is pointed out at some length in 
the article considered, and the argument questioned by Mr. Green- 
wood was built on this absence of equality. The words “ignore” 
and ‘fact ” seem incorrectly applied. 
The question is at present scarcely worth discussion. Mathe- 
matical calculation of the effect is environed with apparently insu- 
perable difficulties. But the rough attempts at calculation which I 
have made lead me to suspect that its amount is insignificant, and 
not even inadequate to alter mean temperature by a degree. 
Sr, Joun’s Cottece, CAMBRIDGE, Avg. 10. E. Hitt. 
SCLEROTIC BONES OF COAL-MEASURE REPTILES. 
Srr,—Would you kindly permit me to inform your readers that I 
have obtained from the Northumberland Coal-measures a perfect 
ossicular sclerotic ring of a Carboniferous reptile? It consists of eight 
ossicles of a quadrate form which slightly overlap each other and 
produce a perfect ring, the central opening of which is 55;ths of an 
inch in diameter; and the extreme diameter of the ring of ossicles 
is ths of an inch. 
I have also obtained a series of six sclerotic ossicles lying in 
regular order. The ring, if complete, indicates the existence of about 
24 ossicles, and the central opening about 2ths of an inch in diameter. 
