Record. xxxv 



2. Generally speaking, male roaches learn more quickly than female 

 and young roaches are more apt than adults; but there are marked 

 individual exceptions to this. 



3. In the ability to learn and to retain what they have acquired 

 roaches exhibit marked individuality. 



4. Roaches that have acquired the habit of refusing to enter a dark 

 place do not lose the habit when they moult. 



5. Roaches that have learned to respond in the manner described 

 continue to respond in that way even when several days elapse between 

 experiments. 



6. During sickness and just prior to death the retentiveness of the 

 roach is much impaired. 



Professor F. E. Nipher stated that lie had recently 

 obtained results which confirm his previous conclusion, 

 that the strength of a steel magnet depends upon its 

 electric potential. He has found this to be the case even 

 when the magnet composed of a layer of fine steel wire 

 is wholly enclosed in a covering of tin-foil. 



February 17, 1913. 



President Engler in the chair; attendance 36. 



The following donations to the Library were reported : 



D. L. Harris. .Five pamphlets on the subject of rabies. 

 A. S. Pearse..Pour pamphlets on crabs. 



Professor F. E. Nipher addressed the Academy on 

 ''Effect of Electrification of Air on its Magnetic Per- 

 meability. ' ' 



Professor Nipher stated that he had recently found that when a 

 steel magnet is insulated and connected to either terminal of an influ- 

 ence machine, the other terminal being grounded, all points in the field 

 of the magnet show an increase in magnetic intensity. There is an 

 apparent increase in the magnetic moment of the magnet. This is 

 really due to an increase in the permeability of the surrounding air. 



The magnet thus acted upon was one of two deflecting magnets, 

 placed on opposite sides of a magnetic needle suspended from a silk 

 fiber, within a metal cylinder. The motion of the needle was observed 

 by means of a telescope and scale, through a small opening in the 

 metal shield, which was closed by a sheet of glass covered with wire 

 gauze. 



One of the deflecting magnets is put in contact with the influence 

 machine. All disruptive effects are to be avoided. The needle shows 

 a gradual deviation from the magnetic meridian, amounting to about 

 four minutes of arc. This result is obtained even when the magnet is 



