38 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
small stop-cock near the upper end to admit air, and another near the 
lower end to discharge the water. 
The apparatus proved entirely reliable, perfectly water tight, and it 
has the great advantage that it can be made by any skilled machinist 
at small expense. The most important precautions in its manufacture 
are to provide tight stop-cocks: and to make the diameter of the tube 
as nearly the same as that of the latter as possible. 
The water samples were preserved in “citrate of magnesia”’ bottles, 
made of lead glass by the Whitall Tatum Co., with patent stoppers 
consisting of a porcelain disc forced by a spring against a rubber ring. 
The joint thus formed is so nearly air tight, that the danger of evap- 
oration is negligible. As pointed out (p. 62) tests show no appreciable 
alteration of the samples after prolonged storage. The only drawback 
to these bottles is that they are fragile and occasionally break sponta- 
neously as a result of sudden change of temperature. 
Current measurements were taken with an Ekman current meter. 
Salinity was determined by titration with nitrate of silver, the index 
being chromate of potassium. ‘The burette and “Knudsen” 3-way 
pipette were supplied by Robert Goertze of Leipzig, the standard 
water by the International Committee for the exploration of the sea. 
This, of course, is the method almost universally employed; and the 
principle on which it depends has been explained by Murray and 
Hjort, (1912) as well as by various other writers. 
The color of the sea is usually recorded by the “Forel” scale based 
on a combination of blue and yellow, the former being .5 gram copper- 
sulphate + 5 cc. ammonia in 95 ec. water, the latter .5 gram potassium 
chromate in 100 cc. water. The combinations used are: — 
1 28 (4 86 6 % 9S 8 (ae 
blue 100 98 95 91 86 80 73 65 56 46 35 23 10 
yellow 0 2 56 9 14 20 27 3 4 4’ GW @ 
In practical use a scale consisting of a series of glass tubes is unsatis- 
factory because of surface reflections. But these are entirely avoided 
if the tubes be mounted in a frame above a white mirror of porcelain 
at 45°, being thus seen by transmitted light against a white back- 
ground. The color of the sea water is observed by means of an ordi- 
nary plate-glass mirror mounted at 45° at the end of a pole and held a 
foot or two below the surface on the shady side of the ship. With this 
device, our home waters change from apparent blue to light bottle- 
green. 
Transparency measurements were made with the ordinary white 
