89 



A Few Experiments with Liquid Air. 

 C. T. Knipp. 



[Abstract.] 

 Three experiments were given, using the liquid as a refrigerant. (1) 

 The resistance of manganin wire at the temperature of liquid air; (2) the 

 absorption of heat by conduction into the liqitid; (.3) the action of a Cu-Fe 

 thermostat wlien placed in the liquid. 



(1) The temperature coefficient of manganin wive was found to agree 

 fairly well with that found by Dewar. Cooling the wire to the tempera- 

 ture of liquid air caused it to undergo no permanent change. 



(2) By connecting a block of copper through a copper rod to a bath of 

 liquid air the temperature of the block of copper can be reduced to nearly 

 that of the refrigerant. This principle enables any intermediate tempera- 

 tiu'e to be maintained. By this method a connecting rod of copper about 

 1^ sq. cm. in area and 20 cm. long froze a cu. cm. of mercury placed in the 

 block of copper in 6^ minutes. 



(3) A Cu-Fe. thermostat was found to be very sensitive, and it was 

 also noticed that the same coefficients hold at the temperature of liquid 

 air. 



The BlTANGENTIAL OF THE QuiNTIC. 

 U. S. Hanna. 



jSTote on an Attempted Angle Trisection. 

 R. J. Aley. 



The Zoological Survey of Minnesota. 

 Ulysses O. Cox. 

 With the establishment of the Geological and Natural History Survey 

 in Minnesota provision was thereby made for collecting and describing 

 the various faunal forms of the State. For a number of years after the 

 survey was established work was done only along geological lines. In 

 1886 there appeared a list of the Aphidae of Minnesota, by Mr. O. W. Oest- 



