RECORDS. 163 



Experiments made with pendulums consisting of a steel ball 

 suspended by a wire, and striking against a steel anvil, gave 

 very positive and satisfactory contacts. Using a pendulum 

 with the suspension wire about four meters long and the steel 

 ball two inches in diameter, an arc, of .5° gave 0.00039 second, 

 while a pendulum with a short suspension wire using one-half- 

 inch steel ball, through an arc of 90° gave 0.000079 second. 



It is interesting to note that in working with condensers the 

 best mica condenser gives no appreciable variation in capacity 

 for the very briefest times of charge, while a paraffiine condenser 

 may show a reduction in capacity of some sixty per cent, from 

 a time charge of 0.4 second to that of 0.00 1 second. 



Professor Bogert's talk was a very interesting discussion of 

 " Some Products Derived from Coal," paying special reference 

 to the products from coal tar. From bituminous coal by dis- 

 tillation are derived (i) coal gas, (2) ammonia water, (3) tar 

 and (4) coke. 



The uses of coal gas and coke are so well known as to need 

 no mentioning. In the United States the total production of 

 ammonium compounds for the year 1900 amounted to 27,000 

 tons, valued at about $2,000,000. 



The chief source of coal tar is the coal gas manufacture, but 

 large amounts are also obtained from the by-product coke 

 ovens, the water gas industry, etc. During the year 1900, 20 

 per cent, of the gas produced in the United States was coal 

 gas, requiring the distillation of 1,350,000 tons of coal, and 

 producing 13.5 billion cubic feet of gas, i. e., 10,000 cubic feet 

 per ton of coal. The yield of tar is approximately 5 per cent, 

 of the weight of the coal used ; the product of tar was there- 

 fore, 67,000 tons. If we add to this the 52,500 tons of tar 

 from the by-product coke ovens, we have a total of about 

 120,000 tons of tar produced in 1900 from coal. This is less 

 than one fifth of the amount produced in England from similar 

 sources. The total production of coal tar in Europe for the 

 year 1898 was i , 1 20,000 tons. 



Coal tar is first roughly divided into the following fractions 



I. First runnings, or light oil (lighter than water). 



