May 1, 1903.] 



SCIENCE. 



707 



March 2, i905.— Professor F. E. Niplier 

 gave an account of his experiments in the 

 production of ether waves by means of ex- 

 plosions. He is now using a brass tube, six 

 feet long and one and one third inches in di- 

 ameter, for the explosive, which is laid in a 

 train from end to end. This tube is placed 

 within a large brass tube, one and three eighths 

 inches in diameter, which is wound with 25,700 

 windings of No. 25 copper wire. This coil 

 is connected with a delicate D'Arsonval gal- 

 vanometer. The coil is placed with its axis 

 in the magnetic meridian. When gunpowder 

 is exploded in the inner tube, the galvanometer 

 gives indication of a change in permeability 

 of the heated channel within the coil. The 

 results were said to be as yet inconclusive, and 

 the apparatus is to be somewhat modified, 

 with a view to making it more sensitive. 



March 16, 190S.—Dr. H. M. Whelpley gave 

 an illustrated account of the sacred pipe-stone 

 quarries of the upper Missouri. 



April 6, 190S. — ^Professor A. S. Chessin pre- 

 sented a communication on the strains and 

 stresses in a rotating thin circular disk. 



Professor P. E. Nipher reported that he 

 had apparently succeeded in producing a dis- 

 tortion of a magnetic field by means of ex- 

 plosions. The apparatus used was a trans- 

 former consisting of concentric coils wound 

 upon brass tubes. The outer tube was five 

 inches in diameter and six feet long, wound 

 with over four thousand windings of No. 16 

 wire. This coil was traversed by a continu- 

 ous current from a storage battery. Within 

 this, and separated from it by an air-space 

 of an inch, is a secondary coil of equal length 

 having over twenty-five thousand windings of 

 No. 25 wire. This coil is connected to a 

 D'Arsonval galvanometer. Within the tube 

 on which this coil is wound is a smaller brass 

 tube, within which a train of black gunpowder 

 is laid. This tube is open at both ends, and 

 has practically no recoil when the explosion 

 is made. When hung by a bifilar suspension 

 on cords ten feet in length, the recoil is about 

 an inch. When the exciting current is small 

 compared with the capacity of the battery, 

 the galvanometer reading is very steady. 



When the train is exploded, a sudden and 

 marked throw of the galvanometer results, 

 which could be accounted for by an increase 

 in the permeability of the long explosion 

 chamber. The deflection reverses when the 

 field in reversed. The hot gases liberated in 

 the explosion are all diamagnetic, and tend 

 to decrease the observed effect. In two eases 

 the galvanometer deflection was in the op- 

 posite direction from that stated above, and 

 this is being further inquired into. When 

 seven tubes between the two coils are simul- 

 taneously exploded, only slight effects could 

 be obtained, and these deflections are waver- 

 ing, or to and fro, in character. A wire was 

 threaded through the inner combustion tube, 

 through which a current of three amperes was 

 passed. This circuit was -opened and closed 

 with no visible effect. The galvanometer cir- 

 cuit is shielded by tin-foil, which is alsQ con- 

 nected with the explosion tube, and grounded. 

 Sparks an inch long to the tin-foil produce 

 no result. When the explosion tube is re- 

 moved from the transformer, and taken near 

 the galvanometer, or the storage battery, no 

 deflection is produced by the explosion. 



An explosive mixture of gases from water 

 electrolysis under atmospheric pressure pro- 

 duces a much less violent explosion, and pro- 

 duces a correspondingly less effect. The scale 

 reading of the galvanometer changes by over 

 twenty divisions with the heaviest explosions 

 and an exciting current of 0.6 ampere. With 

 smaller explosions or feebler currents, the ef- 

 fect is diminished. No deflections can be 

 produced by striking the table upon which 

 the transformer rests, nor by striking the 

 transformer itself, even when it moves slightly 

 under the blow. The secondary and primary 

 coils are held rigidly in fixed position with 

 respect to each other. 



Arrangements have now been made to place 

 the explosion tube in the focal line of a para- 

 bolic cylinder of metal, the galvanometer coil 

 being in the focal line of a similar mirror. 

 Either or both are to be surrounded by an 

 exciting coil. 



This line of research was suggested by 

 Young's account of his observation of five 



