642 REPORT OF COMMISSIONER OF E1SH AND FISHERIES. [38] 



motion, bringing the screw on the upper end of the spindle into action, 

 gradually raising the propeller until the lower end of the spindle is 

 withdrawn from the hole in the cap, ■/, when the thermometer promptly 

 turns over and registers the temperature by breaking the column of 

 mercury at the point a, the column then falling to the bottom of the tube. 

 . ft can be read at any time afterward, as changes of temperature do not 

 affect the reading after the column is once broken." 



The latch, r, and slot, s, in which it works, has been added to pre- 

 vent lateral motion after the thermometer has been turned over. 



THERMOMETERS FOR AIR AND SURFACE TEMPERATURES. 



The instruments for this purpose were made by J. and H. J. Green, 

 ]S T ew York, and are all that can be desired. 



STEAM TRAP. 

 [Plate VIII. ] 



The exhaust steam from the radiators, fore and aft the vessel, is 

 trapped to the hot-well and again fed into the boilers, thus effecting a 

 considerable saving in fuel. 



We first used the Hawes trap, which did not prove satisfactory. The 

 Chapman trap was then tried with better results, but it frequently failed 

 to carry off the water, thus flooding the radiators and causing more or 

 less annoyance. Mr. Baird, coming to our assistance again, devised a 

 simple and inexpensive trap which has performed its work admirably, 

 relieving us from the annoyances above mentioned. 



BOILERS. 

 [Plate IX.] 



Mention has been made of an appropriation for new boilers, made 

 necessary by a contemplated cruise in tke Pacific. The old ones are 

 much worn and require extensive repairs after each trip, making them 

 totally unfit for a long cruise. 



With the introduction of new boilers we will increase the size of the 

 coal-bunkers between GO and 70 tons, thus augmenting the steaming 

 distance over 1,000 miles. A "donkey" boiler is included in the new 

 arrangement, for distilling water, heating and lighting ship, and for fire 

 purposes. Heretofore this service has been performed by one of the 

 main boilers, at comparatively large expense. 



MAIN STAY-SAIL. 



We formerly carried a fore trysail gaff, but owing to the position 

 of the standard compass, pilot-house rail, &c, were unable to use the 

 sail. We Lave recently dispensed with the gall' and substituted a 

 stay-sail, containing 000 square feet of canvas, hoisting on the main- 



