700 General Notes. [ October, 
hopeless, and at the same time a conviction that if their task had 
been practicable by human skill and bravery it must certainly 
have been accomplished. Speaking of the large contributions of 
Prof. Mohn and Prof. Sars, of Norway, to our knowledge of the 
distribution of temperature and the course of ocean currents, he 
remarked that Prof. Mohn spoke highly of the service rendered 
by Negretti and Zambra’s new reversing thermometer, an instru- 
ment so constructed that by a simple mechanical arrangement the 
which the instrument may have passed in descending. In the 
Challenger the want of such a thermometer was greatly felt, for 
in the Arctic and Antarctic seas the coldest layer is frequently 
on the surface, and a warmer belt intervenes between it anda 
bottom stratum. Ata depth averaging perhaps 500 fathoms we 
arrive at a temperature of 40° Fahr., and this may be regarded as 
a kind of neutral band separating the two layers. Above this 
band the temperature varies over different areas; beneath it the 
temperature almost universally sinks very slowly and with 
increasing slowness to a minimum at the bottom. Speaking 
generally, it may be said that the trade winds and their modifica- 
tions and counter currents are the cause of all movements in the 
‘stratum above the neutral layer. One of the most singular 
results of late investigations is the establishment of the fact that 
all the vast mass of water, often upwards of 2,000 fathoms in 
thickness, below the neutral band is moving slowly to the north- 
ward, that, in fact, the depths of the Atlantic, the Pacific and the 
larly its southern portion, the reverse is the case. Thus one part 
of the general circulation of the ocean is carried on through the 
atmosphere, the water being raised in vapor in the northern hem- 
_isphere is hurried by upper wind currents to the zone of low 
barometric pressure in the south, where it is precipitated in the 
_ form of snow or rain. Time would not allow him even to allude 
