DEEP-SEA EXPLOKATION. 
323 
THERMOMETERS. 
Thermometers were procured from various maimfaeturers during the earlier 
operations of the Fish Commission and issued for service without previous comparison 
witli a standard. Only the best instruments of reputable makers were used, and 
observations weie conlined to air temperatures, suiface, shoal water, and moderate 
depths, hence they did not suffer materially until the scope of temperature observa- 
tions enlarged in the direction of the deep sea, when instrumental errors became of 
sufficient frequency to case discredit upon them. 
Systematic and successful efforts Avere made by the officers of the Commission to 
improve this branch of the service; greater care Avas exerciscAl in tlu'. selection of instru- 
ments; makers were informed of Aveak points de\"eloped in service and encouraged to 
remedy them; all thermometers Avere rigidly compared by an officer of the Commission 
and were accompanied by tables of corrections Avheu issued for serx ice. The accom- 
panying description \au11 include only the thermometers of the Albatross^ as they 
represent the types in use on board the vessels of the Commission. 
Thermometer fi for air temperaturoi are made by J. & 11. J. Green, Nexv York. The 
tubes are 10 inches iu length, made extra strong, well seasoned, and graduated on the 
stems to 1° F. They rate with remarkable uiuformity, with a maximum error of 0.3°, 
minimum of 0.0°, and mean of 0.1°. They are mounted in extra heavy copi>er cases, 
open in front, with a cup in the bottom perforated Avith a central hole. 
Wet-hnlb thermometers are the same as those above describetl and are prepared 
for their special function by having their bnlbs enveloped in lamp Avick, which being 
immersed in a suitable cup of fresh Avater placed beneath the suspended instrument 
saturates the fibers surrounding the bulb by capillary attraction.' 
Thermometers for surface temperatures are the saine as before describexl for air, 
and are prepared for use by inserting a cork into the central hole in the bottom of the 
frame. 
The Taejliabue thermometers attached to the Hilgard ocean salinometers are simide 
tubes, with round bulbs, protected by perforated brass cages and fitted to slide into 
the front of the salinometer cup. The older make, graduated on the stems to 1° F., 
range from 30° to 100°, Avhile later forms are graduated to 1° centigrade, and range 
from — 10° to -f- 50°. 
THE NEGRETTI & ZAMBRA DEEP-SEA THERMOMETER. 
The following description is copied in part from the catalogue of Negretti & Zam- 
bra. The construction of the thermometer AA'ill be understood by reference to fig. 2, 
plate XX, and its shield is shown in fig. 2, plate xxi, in a vertical sectional elevation 
of the Tanner deep sea thermometer case. 
The thevmometrical Iluid is mercury; tlie luilh containing it is cylindrical, contracted in a 
peculiar manner at the neck a ; and upon the shape and fairness of this contraction the success of the 
instrument mainly depends. Beyond a the tube is l)ent and a small catcli reservoir at h is foriTied for 
a purpose to he presently explained. At the end of the tuhe a small receptacle c is provided. When 
tlie hulh is downward the glass contains suflicient mercury to till the bulb, tube, and a part of the 
receptacle c, leaving, if the temperature is high, sufficient space in c. AVheu the thermometer is held 
bulb upward, the mercury breaks at «, and by its own weight flows down the tube filling c and a 
portion of the tube above c, depending upon the existing temperature. The scale is accordingly made 
to be read upward from c. 
