[37] WORK OF STEAMER ALBATROSS. 641 



The Negretti-Zambra deep-sea thermometer was described as follows 

 in the Keport ou the Construction and Outfit of the U. S. Fish Commis- 

 sion Steamer Albatross, 1883 : 



"The thermometrical fluid is mercury; the bulb containing it is cylin- 

 drical, contracted in a peculiar manner at the neck «; and upou the 

 shape and fairness of this contraction the success of the insrtument 

 mainly depends. Beyond a the tube is bent and a small catch reser- 

 voir at b is formed for a purpose to be presently explained. At the end 

 of the tube a small receptacle, c, is provided. When the bulb is down- 

 ward the glass contains sufficient mercury to fill the bulb, tube, and a 

 part of the receptacle c, having, if the temperature is high, sufficient 

 space in c. When the thermometer is held bulb upward the mercury 

 breaks at a, but of 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 read upward from c. 



"To set the instrument for observation it is only* necessary to place 

 it bulb downward, when the mercury takes the temperature just as in 

 an ordinary thermometer. If at any time or place the temperature is re- 

 quired, all that has to be done is to turn the thermometer bulb upward 

 and keep it in this position until the reading is taken. This may be 

 done at any time afterward, for the quantity of mercury in the lower 

 part of the tube which gives the reading is too small to be sensibly 

 affected by a change of temperature, unless it is very great; while that 

 in the bulb will continue to contract with greater cold and to expand 

 with greater heat. In the latter case some mercury will pass the con- 

 traction a and fall down and lodge at b, but it cannot go farther so long 

 as the bulb is upward, and thus the temperature to be read will not 

 be affected. . s 



"The thermometer is inclosed in a glass shield which eliminates all 

 errors that might arise from pressure at great depths. 



" To mount the thermometer, unscrew the cap * (Plate IV), drop a 

 spring, h, into the case, slip a thimble, g, over the glass shield at d, put 

 the thermometer in the case, drop in another thimble, which will rest 

 on the upper end of the shield ; then place another spring on the thimble 

 and screw the cap in place. The thermometer will then be suspended 

 between delicate spiral springs at the ends, and soft rubber rings which 

 surround the shield. This arrangement has proved effectual in guarding 

 the thermometer against jars incident to the service required of it on 

 board the Albatross. 



"To take a temperature set the spindle, o, into the hole in the cap, i, 

 by screwing it down until the propeller blades are against the stud p, 

 then by means of the Sigsbee clamp, q, secure it to the temperature rope. 

 The bulb will then be down and the mercury in the tube connected with 

 it, the position required to take the temperature. The water acting on 

 the propeller during the descent will keep it in position, resting against 

 the stud, Pj but as soon as the reeling in begins the propeller is set in 

 B. Mis. 90 41 



