SCIENTIFIC SUMMAKT. 
335 
distance, provided there he alternate condensations and rarefactions, as seems 
to he inevitable ; for it is contrary to known hydrodynamical laws to suppose 
the possibility of a solitary wave of condensation. The above-mentioned 
velocity gives rise to a continual flow from the rarified into the condensed 
parts, and just in the proportion required for altering the law of diminution 
with the distance from the inverse square to the simple inverse. Professor 
Challis believes that the attraction of magnetism is caused by vibration, to 
which he might have added the attraction of gravity— a doctrine long since 
propounded by Robert Hooke, and of which an account is given in his pos- 
thumous works. In the revolving grate erected by Boulton and Watt 
beneath a steam-boiler at the Bank of England, the coal was fed by a scoop 
moved by a cam, which advanced the scoop gradually over an orifice, carry- 
ing coal with it, and then suddenly drew back the scoop, when the coal, by 
its inertia, remaining behind it, fell into the fire. In this case we have a 
backward and forward motion causing bodies subjected to it to travel in a 
certain direction ; and if we suppose a similar motion to exist in the 
particles of bodies, an attraction like that of gravity will be the result. — 
Society of Arts Journal. 
Physics of Arctic Ice. — Mr. Brown has published, in the u Quarterly 
Journal of the Geological Society” (February 1871), a very long and im- 
portant paper on the above subject, especially as regards Scottish geology. 
The author concludes : — 
(a.) That after the Tertiary period the country was covered with a great 
depth of snow and ice, very much as in Greenland at the present day 5 but 
possibly some of the mountain-tops appeared as islands. During this and 
the subsequent period glaciers ploughed their way down from the inland ice, 
and icebergs broke off and reached the sea through the glens, then ice-fjords. 
(/3.) After this the country sank gradually, as Greenland is now sinking, 
to the depth of several hundred feet ; and during this period most of the 
glacial laminated fossiliferous clays were formed. During this period 
boulders were deposited from the icebergs broken off from the glaciers of 
Scotland, as well as from the icebergs and other floating ice drifted both 
from the north and south, as was also the case during the former (a) period. 
(7.) The country seems then to have emerged from the water, but no 
doubt slowly, until the glaciers finally left the country. 
(1) By this time the country was much higher than now, and the land 
being connected with the continent, the bulk of the present flora and fauna 
crept into it from various quarters, though the alpine plants still kept posses- 
sion of the higher mountain-regions during a great portion of this epoch. 
(f.) A depression now took place, and the estuarini beds, or carses , of the 
Scotch rivers were formed. Much of the fossiliferous boulder-clay was 
formed as he has described it ; is now under the sea ; off the coast remains 
of its fauna are continually dredged up. Man had also by this time got into 
the country. 
(£.) The land after this seems to have risen, in all probability, to its pre- 
sent level, for we have no certain evidence that since the dawn of history 
there were any oscillations of level. 
A Temporary Accidental Fountain . — M. H. Vogelsang gives, in Poggen- 
dorff’s “Annalen” (No. 2, 1811), a long account of a curious fountain 
