320 Scientific Intelligence. 
per cent, but the residue gave a heavy precipitate with silver 
nitrate when examined by Rose’s method. It was found that 
only a very small quantity of the chlorides escaped at a high 
_red heat, a white heat being required to expel them in large 
quantity, although even at that temperature some remain as 
proved by the last experiment. bout half a gram of the 
finely powdered mineral was treated with cold distilled water 
for about forty-five hours, but not a trace of the chlorides 
went into solution. The scapolites mentioned in the table, 
which contain the highest percentage of chlorine, are generally 
sound and undecomposed. ‘T'wo specimens of the Ripon min- 
eral, with little or no luster, were found to contain less chlorine 
than an undecomposed specimen with a high lustre. Fuchs 
states that the “ Porzellanspath,” examined by him, lost a por- 
tion of its chlorides on decomposition. The specimen from 
Hull, which contained only -202 per cent, was almost entirely 
devoid of lustre and contained carbon dioxide. It is therefore 
highly probable that chlorine is lost, and not gained by the 
decomposition of the scapolite minerals. 
It is possible that in some cases at least the failure of scapo- 
lites to give a good formula, may be due to the fact that suffi- 
cient alkali to combine with the undetermined chlorine present 
has not been deducted before attempting to deduce the formula. 
My best thanks are due to Professor Allen, who has kindly 
directed this investigation. 
SCIENTIFIC INTELLIGENCE. 
I. Puysics. 
1. On the Formation of Mountains and the Secular Cooling 
of the Earth ; by G. H. Darwin.—The letters of Mr. Wallace 
and Mr. Fisher in Natwre, vol. xix, pp. 121, 172, 244, 267, raise 
the question as to whether or not it is possible that the interior © 
the earth can be cooling more rapidly than the exterior. The 
following is an attempt to answer the query as to where the loss 
of temperature per unit of time is greatest. 
ir W. Thomson (see Thomson and Tait, “ Nat. Phil.” App. D) 
considers the cooling of “a solid extending to infinity in all direc- 
tions, on the supposition that at an initial epoch the temperature 
has had two different constant values on the two sides of a certain 
infinite plane.” The solution given is— 
Baus oy. —F_ cee 
Pe ied: 2J (kt) ; z Pt 
0 
be k denotes the conductivity of the solid, measured in terms 
4 
F 
“ 
fi 
Se at ase ee 
of the thermal capacity of the unit of bulk; V, half the difference : 
