[81] FJSHEEIES OF THE UNITED STATES. 593 



tion is interposed. It passes between the inner extremities of the slip- 

 hooks, and controls their opening and closing. When the spindle is 

 screwed up so that the blades are close to the cap, the smaller or cone 

 end of the spindle is between the hooks, and allows them to open freely. 

 As the motion of the spindle is reversed, however, the broader part is 

 gradually forced between the hooks, causing their outer ends to come 

 together and bind closely. A fulcrum attachment above the hooks per- 

 mits of their being raised and opened, even when they are otherwise 

 locked by the spindle, for the purpose of inserting the sounding wire. 

 In the water the movem ents of the spindle are entirely controlled by 

 the propeller blades. 



To prepare for use, the sounding wire is clamped at the lower end 

 of the case, as before described, and passed through the opening be- 

 tween the slip-hooks, which are locked by screwing down the spindle. 

 The case is now ready for lowering. As it passes down through the 

 water, the upward current produced through the cylinder tends to keep 

 the hooks locked by the force it exerts against the blades. As soon, 

 however, as the reeling in begins the direction of the current is changed, 

 the blades revolve in the opposite way, screwing the spindle up through 

 the nut until the cone end comes between the hooks, when the latter 

 open, release the wire, and the tripping is accomplished. Again, the 

 relative direction of the current is altered, and when the case reaches 

 the surface the hooks will be found locked and ready for use without 

 the necessity of screwing down the spindle by hand, the fulcrum at- 

 tachment furnishing the means of opening the hooks for the insertion 

 of the wire. "Were the blades given free play through the entire length 

 of the cylinder, they would require to traverse about fifty fathoms before 

 loosening the hooks. This extreme amount of play is allowed to insure 

 against the tripping of the case by the violent pitching or rolling of the 

 ship, and may be lessened to trip in any distance, down to one fathom, 

 by means of a long, slender screw which enters the cylinder from be- 

 low on one side. To further insure the propeller blades recovering in 

 descent all the revolutions expended in the upward motion of the ship, 

 in rolling or pitching, the blades are bent over at the top a distance 

 of about one-eighth of an inch, at the same angle as the blades them- 

 selves, thus giving them more pitch with the current from the bottom 

 than from the top, and compensating for the oblique action of the 

 water through the broad slots at the lower end of the cylinder. 



This style of thermometer case may be used as the upper one of a 

 series for taking serial temperatures in deep water, the others being of 

 the first described pattern and tripping in the same way. 



Sigsbee's Water Specimen Cup, for obtaining specimens from a number 

 of depths at a single haul. 

 Commauder Charles D. Sigsbee, United States Navy. 



•It is believed that this is the only cup ever devised for this special 

 purpose. A discussion of the cup and its operation is contained in Sigs- 

 2444— Bull. 27 38 



