73 
that the floor of the Atlantic is covered by a creamy, floccnlent 
layer of microscopic animals ; whilst, wherever there is any known 
current, this deposit is absent and replaced by gravel, and thus show's 
that the movement of any cold indraught of water at the bottom 
must be excessively slow. He dispels the chimerical idea that there 
is a kind of equatorial diaphragm between the northern and southern 
ocean basins, and explains that it is only on the surface of the sea 
that a line is drawn between the two hemispheres by the equatorial 
current. He then gives as evidence of the slow indraught of cold 
water from the Southern Sea, that it is colder than the mean winter 
temperature of the area which it occupies and that of the crust of 
the earth, and that its temperature rises as it is traced northward ; 
whilst, owing to Behring’s Straits being only 40 fathoms deep, 
there is no adequate northern source of such a body of cold water. 
In 1869 Wyville Thomson was elected a Fellow of the Royal 
Society; and in the year following, on the resignation of Dr 
Allman, he was appointed Professor of Natural History in the Uni- 
versity of Edinburgh. His friends in Belfast recognised the dis- 
tinction which had thus been conferred upon him, but felt the 
loss which the college and the town had sustained by his re- 
moval, and, on taking leave of him, presented him with a handsome 
service of plate and an illuminated address at a public meeting pre- 
sided over by the mayor. The honorary degree of D.Sc. was 
conferred upon him by the Queen's University about the same time. 
His duties now became more arduous than ever. His class-room 
was crowded with students, whom he taught not merely by lectures 
but by practical demonstrations. In 1871, the meeting of the 
British Association in Edinburgh, the arrangement and plans of 
the new University buildings, troubles in connection with the 
admission of females to the college classes, and the transfer of the 
Museum of which he was Regius Keeper, to the Museum of Science 
and Art, added greatly to his necessary labours. 
At this time the rapid extension of ocean telegraphy gave prac- 
tical value to everything which concerned the depth of the ocean, 
the character of its bottom, and the presence there of animals which 
might injure the coverings of telegraphic cables, whilst great interest 
was being manifested by the public in the remarkably novel experi- 
ences of the cruises of the “Lightning” and the “Porcupine.” 
