866 Transactions- of the American Institute. 



cliaro-e of the electricity through some thinner portion of the prlass. 

 He did not consider a comparison made by Dr. Edwards between the 

 condition of a char-ed Leyden jar and the earth as very apropos. 



Dr Vandermeydesaid: When we consider that our earth is cov- 

 ered with water for three-quarters of its surfece ; and that ram is 

 fallino- nearlv all the time, which keeps the ground moist ; and the 

 law that we "observe in mines that the temperature increases with the 

 depth and we know that heat will convert water into steam, and 

 when this water penetrates through crevices and there converted into 

 steam, we know a vent will be found, and a shock or an eruption wil 

 en.ue The interior of the earth being Hquid, and the exterior of unequal 

 thickness, a rupture will take place at the weakest part. The crust 

 may be one mile, or one hundred miles in thickness. It has been 

 observed that after a rainy season there i» more probability ol earth- 

 quakes and mountain eruptions. 



The discussion was continued until a late hour, when it was 

 announced that, as the next Thursday was set apart ofticially as a 

 day of thanksgiving, the association was to stand ad.iourned to 

 December 3d. 



December 3, 1868. 



Professor S. D. Tillman in the chair ; Mr.C. E. Emeky, Secretary. 



Self-KecordinCt Steam Indicator. 



Mr Clark exhibited Clark & Edson's apparatus for recording the 



pi^easure of steam in the boiler of a steam engine ; also the diagrams 



made by it. He stated that by its peculiar construction the following 



advantages are obtained : 



Ist It records continuously the actual condition of, and every 

 variation in, the pressure of steam upon a card or chart, which can be 

 preserved for future reference. ^ 



2d. It records the actual time upon the chart from which the revo- 

 lutions of -the engine may be calculated whenever desired. 



3d. It beino- of .a superior construction it is reliable as a test guage. 

 4th By pkcing the instrument in the office a proprietor or super- 

 intendent can at aU times know the actual condition of affairs. _ 



These indicators are applicable to locomotive, marine and stationary 

 boilers. A\^e shall -be. happy to show an instrument in operation at 

 our oiUcew 



