SCIENTIFIC SUMMARY. 
487 
the earth to be formed of the same ingredients as the exterior, minus oxygen, 
chlorine, bromine, &c., a specific gravity of 5 to 6 would not be an unlikely 
one. Many of the elementary bodies entering largely into the formation of 
the earth’s crust are as light or lighter than water, — for instance, potassium, 
sodium, &c. ; others, such as sulphur, silicon, aluminium, have from two to 
three times its specific gravity ; others, again, as iron, copper, zinc, tin, seven 
to nine times ; while others, lead, gold, platinum, &c., are much more dense — 
but, speaking generally, the more dense are the least numerous. There seems 
no improbability in a mixture of such substances producing a mean specific 
gravity of from 5 to 6, although it by no means follows, — indeed the pro- 
bability is rather the other way, — that the proportions of the substances in 
the interior of the earth are the same as on the exterior. It might be worth 
the labour to ascertain the mean specific gravity of all the known minerals on 
the earth’s surface, averaging them in the ratios in which, as far as our know- 
ledge goes, they quantitatively exist, and assuming them to exist without the 
oxygen, chlorine, &c., with which they are, with some rare exceptions, invari- 
ably combined on the surface of the earth. Great assistance to the know- 
ledge of the probable constitution of the earth might be derived from such an 
investigation.” 
We have received from M. Hermann Goldschmidt a paper on the physical 
constitution of the sun, in which he broaches an original and somewhat 
startling hypothesis, which is something like this : — 
If the sun is travelling along an orbit in space, as we suppose, and in the 
direction we suppose, it is next to impossible that the axis of rotation we see 
is the real one. Therefore there is a nucleus inside the photosphere with an 
axis of rotation differing from that of the photosphere. The nucleus is a 
spheroid, and its axis is inclined at an angle of 20° or 25° to the orbit of 
translation through space. M. Goldschmidt ascribes the production of the 
spots to the attraction between the spheroidal nucleus rotating on one axis and 
the spherical photosphere rotating on another, and this he does in a manner 
which is certainly ingenious if it be sound physically. At all events, those of 
our readers who can obtain access to M. Goldschmidt’s brochure will do well 
to read it. 
We have two other communications on the sun to notice, one by M. Faye, 
the other by Mr. Huggins. M. Faye is rather disappointed that in England, 
where he acknowledges the physics of the sun are studied more than anywhere 
else, we will not accept his theory, more especially with regard to the spots. 
He remarks, “We know that gases heated nearly to the luminous point, do 
not raise themselves to the incandescent state. (This seems to be a property 
belonging to solid bodies, even when reduced to the most extreme tenuity. 
Imagine, therefore, a gaseous medium, on the surface of which is formed by 
chemical condensation, little clouds of incandescent particles, and you have a 
faithful representation of the photosphere. If from any cause clouds are 
wanting in any particular region, that region will appear dark ; there will be 
a spot between the neighbouring clouds ; there will be small intervals, much 
less bright and almost dark. 
“ To this it is objected that, if gases emit but little light, they are at all 
events transparent ; if, therefore, we get an opening in the photosphere, we 
ought to see the photosphere of the opposite side, through the gaseous interior 
