54 • BULLETIN OF THE 



of mercury very nearly. He said that theory, upon the hypo- 

 thesis that the fluid would always have time to assume the state 

 of a static equilibrium of the forces, would require that there 

 should be a change of about 13.5 inches of mean level to one of 

 mercury, and that a cliange of about ten inches of mean level to 

 one inch of mercury had been obtained from the Liverpool tidal 

 observations. He thought the small coefficient in the case of the 

 Boston tides might be due to the shallowness of the water in the 

 harbor and channel leading to the tide gauge, since the shallower 

 the water, the greater must be the velocity of displacement in 

 assuming the state of static equilibrium belonging to a given 

 change of mean level in any given time, and consequently in this 

 case the periods of the oscillations of mean level may be too 

 short for the fluid to assume at any time the state of static equi- 

 librium even approximately. 



With regard to the effect of the winds upon the mean level of 

 the ocean in the harbor, he found that the winds from N. W. 

 around by S. W. to S. E. depressed tlie mean level, the maximum 

 depression belonging to S. W. winds where the depression is but 

 little more than two inches for a wind of average force. On the 

 contrary, the winds from the N. W. around by the N. E. to the 

 S. E. raise the mean level about the same amount, the maximum 

 belonging to the N. E. winds. 



We also find that S. W. winds depress the barometer about one- 

 twentieth of an inch on the average, and N. E. winds raise it 

 about the same amount. The monthly averages of the barometer 

 were least in March and greatest in September, the range being 

 about 0.2 inch, and the -average very nearly 30.10 inches at the 

 level of tide water. 



Mr. C. E. DuTTON gave 



AN ACCOUNT OP SOME RECENT EXPERIMENTS ON DIFFERENT KINDS OP 

 GUNPOWDER AT FORTRESS MONROE. 



Prof. Porter, of Belfast, Ireland, gave an account of 



RECENT EXPLORATIONS IN SYRIA UNDER THE AUSPICES OF THE PALES- 

 TINE EXPLORATION FUND. 



27th Meeting. May 18, 1872. 



Vice-President W. B. Taylor in the Chair 

 Mr. G. K. Gilbert read a communication 



ON certain RECElNT geological AND GEOGRAPHICAL RESEARCHES IN 

 ARIZONA AND NEVADA. 



