-120 
is Cretaceous, while that of Greenland is regarded as Miocene; 
but the close correspondence is curious. 
Pror. D. S. MArtTiIn remarked upon the geological posi- 
tion of this Disco lignite, and its association with Miocene 
plant remains, as described by Prof. Heer (Brit. Assoc., Exe- 
ter, 1869), such as Magnolia, Liquidambar, Sequoia, ete., very 
closely related to our own existing species. This is, doubt- 
less, one of the many localities where the great Miocene flora, 
so close to that of North America at the present day, has left 
the record of its wide extension oyer what are now the 
frozen wastes of the Arctic zone, indicating the prevalence of 
a mild climate and a rich vegetation, throughout the whole 
of the far North, and the probable existence of a land-connec- 
tion by way of Greenland, Iceland, etc., between our own 
continent and Europe. 
Pror. A. K. Eaton read a paper on the ‘Construction of 
the Spectroscope,” reviewing the history of the instrument in 
its several forms, and also presenting some important improve- 
ments and simplifications devised by himself For a direct- 
vision spectroscope, he uses a single bisulphide of carbon 
prism, right-angled, and with a thick glass plate fastened up- 
on its hypothenuse side in such a position that the rays shall 
be refracted into or out of the prism, by total reflection from 
the inner surface of the glass plate, entering or leaving through 
one of its ends, which are beveled so as to form a right angle 
with that face of the prism to which the plate is attached. 
There are thus two modes of transmitting light through this 
instrument; and the resulting dispersion is very different in 
the two cases. When the rays enter one of the opposite sides 
of the prism, and pass out through the edge of the plate, a 
dispersion is obtained four times as great as when they take 
the reverse course, entering on the end of the plate, and 
emerging on the opposite side of the prism. 
The power of this simple spectroscope is very great indeed, 
On a screen ten feet distant, it projects a spectrum of eight 
feet long, in which a hundred lines may be counted. Used 
for direct vision, a number of lines are discernible even by 
