Proceedings of the Polytechnic Association. 805 



tact with oil, always produce violent ebullition. These laws are the 

 same with hydrocarbons distilled under the ordinary atmospheric 

 pressure, as with those distilled in a vacuum or under increased 

 pressure. In the last two cases the variation of the boiling point cor- 

 responding to these different degrees of temperature has been taken 

 into consideration. 



After a discussion of points suggested by the foregoing articles, 

 the association adjourned. 



October 1, 1868. 



Prof. S. D. Tillman in the chair ; Mr. C. E. Emeby, Secretary. 



]^EW Water Meter. 



Mr. Groesbar exhibited his new water meter, the piston and valve 

 being made in one piece. There are two rollers of round India rub- 

 ber wliich roll over the piston. 



Mr. Emery said he was present at the last trial of meters, and it 

 was quite interesting to see the variety of machines constructed to 

 measure water. He believed that a good meter was a mere question 

 of mechanical skill. The piston meters will undoubtedly be the best 

 ones. The screw meter was not a success. The only patents that 

 can now be obtained for water meters are for the valves. 



Mr. Stetson remarked that there are so many different conditions 

 required in a meter, that one to answer all purposes is very difficult. 

 In some places a meter is wanted to measure water very accurately, 

 and at other places exactness is not so much cared for. At Boston 

 they are so situated that they can afford water very cheap, but in 

 Brooklyn it is expensive, and hence it will pay to have a cheap meter. 



Dr. Yanderweyde thought the screw meter almost worthless where 

 accuracy is required. The one here exhibited appeals to be a very 

 ingenious one, and deserves more than a passing notice. 



]tTEw Method foe Eemembering Historical Events. 

 Mr. ISTapoleon Zaba explained his method of studying history. The 

 system of Mr. Zaba is mnemonic, and is taught by means of a series 

 of diagrams, which should be here presented in order to make the 

 subject understood. The speaker occupied a half an hour, and suc- 

 ceeded in convincing some of his audience that this plan for retaining 

 history was feasible. 



