V. 



Novefnber iSlh, 1886. 



President Niphtr in the chair; fourteen members present. 



Mr. Wheeler called attention to the occurrence of carbonic acid 

 in the New Almaden quicksilver mine, in California, where it is 

 met with in considerable quantities in the lower workings. It 

 occasions much trouble and involves considerable extra expense 

 in the ventilation of the mines. 



Dr. Sander exhibited some specimens of sand obtained from the 

 borings of a well at Golden City, Ark. Analysis showed that 

 1625 mg. of the sand contained 90 mg of gold, or 11^ pounds 

 per ton. 



Dr. Curtman announced through the Secretary that he had 

 succeeded in finding a very delicate test for aniline colors. He 

 inverts Hoflman's Tso-nitute reaction for chloroform and thus 

 shows the presence of fuchsine, methyl, violet, etc., in red wine, 

 fruit, syrups, candies, or textile fabrics, in a very sharp manner. 

 He takes a teaspoonful of the suspected red wine and adds one 

 drop of chloroform and about a teaspoonful of caustic potash so- 

 lution, and heats them gently for some time in a test tube. After 

 one or two minutes he boils the mixture, and the peculiar pene- 

 trating odor of the benzoiso-uitrite is readily perceptible. 



December 6th ^ 1886. 



President Nipher in the chair ; eleven members present. 



Prof. Nipher gave an explanation of Kapp's new method of 

 predicting the characteristics of dynamo machines and motors, 

 so that the performance of such machines can be well determined 

 from the drawings of the machine : 



The relation between electro-motive force, magnetizing current, and 

 speed, determines a surface. If the machine contained no iron, or if the 

 multiplying eiTects of the iron were the same at all degrees of magnetiza- 

 tion, the equation of the surface would be ^ = KNC (i). 



Were E= electro-motive force, iVspeedofthe armature, and C mag- 

 netizing current — this is the equation of a hyperbolic paraboloid. 



As C rises the electro-motive force at constant speed is found to rise 

 less rapidly than is called for by the above equation. Kapp assumes that 

 the magnetic resistance of the iron increases as the iron becomes satura- 

 ted. Calling Z the number of lines carried by the magnetic circuit, NC 



