21 
copies of which may be had of the Secretary. The nucleus of a 
good scientific library for the use of members has been formed, and 
contains already some valuable works. ‘The number of members 
is 99, and the balance sheet shows eight pounds in favour of the 
society. Next came the election of a President, Dr. FitzGerald 
having resigned at the previous annual meeting and no one having 
been appointed in his place. He was present in the chair, aowever 
that evening, and proposed as his successor Dr. Thomas Eastes, 
whose name was warmly received and who was unanimously elected. 
The same Vice-Presidents as before were chosen, and also the 
committee, to which latter were added the names of Mr. Hambridge, 
Mr. S. Hills, and Mr. A. H. Ullyett. Mr. Kerr remains Secretary 
of the microscopical section, and Mr. H. Ullyett, General Secretary. 
Business matters were succeeded by the second part cf Mr. H. 
Ullyett’s lecture on the Ice Age, illustrated by lantern slides. After 
giving a brief description of ice and ice phenomenas as at present 
displayed in Greenland, India, and Switzerland, he proceeded 
to give the generally accepted 
CAUSES OF AN ICE AGE. 
About the causes of these glacial periods there have been many 
theories, ¢.g.: (a) That the solar system, in its journey as a whole 
through space, passes threugh regions of varying temperatures ; 
(b) That the hot and cold ages are caused by the changes of position 
in the earth’s axis ; (c) By varying elevations of the continents and 
by change of positions of land and sea; (d) The astronomical 
explanation connected with the name of Dr. Croll, and more fully 
worked out lately by Sir Robert Ball. 
It would be impossible for us this evening to enter fully into all 
these theories and to point out their probability or improbability. I 
shall therefore confine what little I have to say to the last, the 
astronomical theory, so extensively held at the present time, 
although many good authorities are beginning to fall back on some 
of the others, notably the varying elevation of the land. 
To make this theory of Dr. Croll’s perfectly clear, it is necessary 
to enter to a slight extent upon the astronomical relations of the 
earth. The path described by the earth in its yearly journey round 
'- the sun is called its orbit; the path which the sun, in consequence 
of the earth’s movement appears to describe, is called the eliptic. 
It is important, in connection with our explanation, to bear in mind 
that the earth’s orbit is not a circle, although it does not differ 
much from that figure. It is actually an ellipse of small eccentri- 
city, by no means the exaggerated ellipse which is often so mis- 
