Pboceedings of the PoLYTEcimic Association. 973 



end. On striking the bottom, tin's weight is automatically detached, 

 and at the same time provision is made for preventing any further 

 rofation of tlie vane, whereupon the apparatus is brought to the sur- 

 face by a spherical float at its upper end, no line being used with the 

 device. 



Dr. P. H. Yanderweyde remarked that it would be best if the 

 float was formed of a number of small hollow glass spheres inclosed 

 in a perforated metallic globe, inasmuch as these would resist the 

 enormous pressure of tlie water at great depths much better than a 

 single large sphere of the same floating power. 



Prof J. A. Whitney stated that Morse, in experimenting with 

 globes, subjected hollow glass spheres to a pressure of some Ave tons 

 to the square inch. 



Mr, C. E. Emery said that Captain Trowbridge, of the United 

 States Engineers, experimented with an instrument much the same 

 as Mr. Bogardus', with the exception of the float. The long screw 

 in Mr. Bogardus' apparatus does not work well in practice. Four 

 blades of one-quarter the length of the one in this instrument 

 would be much better. On Trowbridge's apparatus, which was 

 much simpler than this, a catch was arranged to prevent the screw 

 from turning when the fluat began to ascend. The instrument is 

 used with a line. 



The Chairman read the following interesting summary of scientific 

 news : 



ETeat of the Stars. 

 Mr. ITuggins has given to the Royal Societ_y of London the results 

 of a series of observations made by him for the purpose of determin- 

 ing whether a measurable amount of heat is radiated from the fixed 

 stars. A thermo-electric pile was arranged so that its surfice was in 

 the focus of a telescope having an object-glass of eight inches aper- 

 ture, and connected with clock-work which kept the image of the 

 star on the face of the pile. When the telescope was directed to cer- 

 tain stars, the needle of the delicate galvanometer attached to the pile 

 was seen to move after a minute or two, and Avhen the telescope was 

 held until the image of the star passed off the needle soon returned 

 to its normal position. The mean of from twelve to twenty obser- 

 vations gave a deviation of the needle by Sirius^of two degrees, by 

 Regulus of three degrees, and Arcturus, after the lapse of fifteen 

 minutes, of three degrees; that by Pollux was one and a half 

 degrees, while Castor produced no perceptible movement of the 



