4 
POPULAR SCIENCE REVIEW. 
currents serial temperature should be taken, either with the 
instrument of Siemens’* or with a Miller-Casella thermometer. 
Simple determination of the depth of the sea at regular dis- 
tances is of primary importance. 
The surface temperature of the sea as well as of the air (de- 
termined by dry and wet bulb thermometers) is to be recorded 
every two hours. The records obtained should be reduced to 
curves. 
In the North Atlantic there seem to be the following strata : — 
(a) Superficial, of which the temperature rises with the at- 
mosphere. This does not exceed 100 fathoms in depth. 
( b ) An upper stratum beneath this ; the temperature of 
which slowly diminishes as the depth increases to several 
hundred fathoms. In the higher latitudes this is considerably 
above the normal of latitude, but in intertropical regions it is 
considerably below the normal. 
(c) A stratum in which the rate of diminution of temperature 
is rapid, after being 10° in every 200 fathoms. 
(d) The whole of the deeper part of the North Atlantic below 
1,000 fathoms is believed to be occupied by water not many 
degrees above 32° Fahr. The glacial stratum. 
An interesting question is the extent to which colder, and 
therefore heavier, water may run up-hill on the sides of decli- 
vities. The position of the Azores is favourable for the deter- 
mination of this. 
The greatest results are expected from the Southern Ocean. 
The specific gravities of surface and of bottom water are to be 
compared, and that of intermediate depths, when serial sound- 
ings are taken. 
The degree of transparency of the water should be deter- 
mined by Siemens’ photographic apparatus, and by lowering a 
white plate to measured depths. 
Observations should be made on the relation, discovered by 
Professor Schouw, between barometric height and the lati- 
tude of the observation. It seems that there are certain 
meridians of high and of low pressure. 
The thermometer and barometer should be observed every 
two hours. Tidal observations may be made by means of a 
graduated pole. 
It is desirable, when enough tidal observations have been made, 
to settle the mean level of the sea, and that a permanent beach- 
mark should be established, recording the date and height above 
such mean level. 
Samples of sea-water should be collected at various depths. 
* Mr. Siemens' instrument is very useful for serial measurement, as it does 
not require to be hauled up for each reading. 
