xxxvi Trans. Acad. Sci. of St. Louis. 



are balanced under all circumstances. He suggests that the forces 

 which cause positive and negative ions in discharge through gases 

 and liquids to move in opposite directions are active in a metal con- 

 ductor. 



Professor C. A. Waldo gave an interesting demonstra- 

 tion of how the Russian peasants can multiply any two 

 numbers, provided they know how to multiply and divide 

 by two. 



For example, it is desirable to multiply 69 by 49. Divide 69 by 2 



and multiply 49 by 2. Continue this process as indicated: 



69 49 



34 98 



17 196 



8 392 



4 784 



2 1568 



1 3136 



Then cancel in the second column all numbers opposite even quan- 

 tities in the first. Add the remaining figures, which will give 3381. 

 Multiply 69 by 49 according to the regular method and the result will 

 be the same, 3381. 



Mr. Albert Briggs Lawver was elected to membership. 



April 15, 1912. 



President Engler in the chair ; attendance 65. 

 Professor A. S. Langsdorf addressed the Academy on 

 * ' Transient Electrical Phenomena. ' ' 



The speaker showed that in most mechanical systems there is 

 stored a certain amount of energy, this energy being potential in 

 the case of stationary systems and kinetic in the case of moving 

 systems. When such a system changes from one condition to an- 

 other, the amount of the energy stored in it also undergoes a change 

 in magnitude, and this increase or decrease of energy must take 

 place in a finite time. The period during which the change of 

 energy occurs is the transient period. In some cases the energy is 

 stored in only one form, as for instance, kinetic energy (a moving 

 train being an example), and this energy must be gradually dissi- 

 pated in bringing the train to rest. In other systems the energy may 

 exist in two forms, potential and kinetic, as for instance, in a pen- 

 dulum, and in such a case the dissipation of the stored energy may 

 take place by an oscillation of the system. 



Electrical circuits are in many respects analogous to the above 

 forms of mechanical systems. Energy may be stored in one form 

 only, such as magnetic energy only, or electrical energy only, or it 



