340 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Example I. Example II. 
o 
23.0 
— 0.1 
o 
10.5 
^ 2 
obs. temp. 
corr. to thermometer. 
22. 9 
102L 00 
— 0. 20 
10.3 
1029. 29 
-f.12 
corrected temii. = t. 
observed hydr. reading, 
corr. for expansion of bydr. =«. 
corr. for hydrometer constant. 
1020. 80 
1023. 99 
1029. 41 
1026. 92 
observed density at <=OU. 
density of standard water at < = 
— 3. 19 
1.018 
-f-2. 49 
.987 
OD — SD. 
m, tabular multiplier. 
— 3.25 
1026. 00 
-f 2. 46 
1026. 00 
m (OD — SD). 
standard water at 15° C. 
1022. 75 
1028. 46 
corrected density at 15°. 
SD. 
For observatiou.s whicli have been reduced to 60° F., made with the old hydrometers indicating 
densities referred to pure water at 60° F., it will suflice to subtract the constant 0.82 from the result 
in order to convert the latter into absolute densities at 15° C. 
Example: Given 1024.00, the density of salt water at 60° F. referred to pmre water at 60° F., 
1024.00—0.82 = 1023.18, its density at 15° C. 
The above plan of decimal notation in Examples I and II, also in the table, is 
adopted for the sake of simiilicity and convenience. The corrected densities will, 
however, be recorded in the customary manner, as follows: 1.02275 — 1.02846. 
The remarks on reduction of observed densities, the illustrative examples, and 
table for reducing densities of sea water to 15° 0. are taken from Bulletin No. 18, 
United States Coast and Geodetic Survey. 
SIGSBEE’S WATER-SPECIMEN CUP. 
The Sigsbee water-specimen cup (i>late xxiv) or water bottle is designed to bring 
a siiecimen of water from any desired depth for the purpose of analysis or to determine 
its specific gravity. The valves are closed mechanically and can not be opened again, 
except by hand. Therefore these cuiis may be used in series, any desired number 
being sent down on the same line. The water bottle is made of brass, except such 
parts as are mentioned as being made of other metals. The following remarks upon 
its working are taken from Sigsbee’s Deep-sea Sounding and Dredging, page 93. 
To adjust the valves hold the upper valve firmly, and unseat the lower valve by .screwing it 
upward, the key (fig. 5) being applied to the lower end of the valve stem / for the purpose. Then 
maintaining the upjier valve on its seat with the finger, or, better, by turning the screw cap down 
upon it, reseat the lower valve gently. In general it will be necessary to adjust the valve only after 
the cup has been taken apart for cleaning or other purposes. 
The cup when in use comes to the surface filled with water, the screw cap pressing upon the upper 
valve, thus securing both valves, and the propeller resting upon the screw cap. To remove the speci- 
men from the cup first lift the propeller, and by giving it a few turns cause its threads to engage the 
screw threads on the shaft; then turn up the screw cap until it uncouples. With the cap in this 
condition the valves may be lifted and the water discharged. When the screw cap is jiressing upon the 
Tipper valve, the threads inside the former are engaged with the threads of the shaft, but on screwing 
u]) the cap, when its lower thread clears the upper thread of the corresponding series on the shaft, 
the cap is uncoupled, which prevents any mistake being made at thisiioint by the person handling tbe 
cup; afterwards tlie screw cap may be turned in the same direction indefinitely without jamming or 
changing its position on the shaft. 
