122 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



daily number of observations lias varied at different times 

 from one to live. At present, according to a system adopt- 

 ed at the beginning of 1877, the hours of observation are 8 

 A.M., 2 P.M., and 8 P.M. The observations consist of read- 

 ings of the barometer, and of the dry- and wet-bulb maximum 

 and minimum thermometers, as well as of notices of wind, 

 clouds, rainfall, aurora, and zodiacal light. Meteors are not 

 ordinarily observed unless they attract attention by their 

 brightness, or some other peculiarity ; and the same remark 

 applies to other miscellaneous phenomena. For some months 

 past frequent observations have been made in the evening, 

 with the object of numerically determining the coefficient 

 of atmospheric absorption. An observation of this kind con- 

 sists in the selection of two stars differing considerably in 

 altitude and apparently of equal brightness. Knowing the 

 true excess in brightness of the lower star, and determining 

 the altitudes of both from the time of the observation, we 

 can deduce the numerical value of the quantity required. 

 Professor Langley intends to adopt this method in his obser- 

 vations at Mt. ./Etna, and I hope that it may also be tried 

 elsewhere." 



The following notes on the year's work of the New York 

 Central Park Meteorological Observatory have been kindly 

 furnished by Dr. Draper: 



The report of the New York Meteorological Observatory 

 in Central Park, for the past year, by Daniel Draper, contains 

 the usual tables from the self-recording instruments, and also 

 a discussion on the two following questions : 



1st. "Has there been in late years a change in the rainfall 

 of New York City or its vicinity, affecting seriously its wa- 

 ter supply?" 



It was found by the observations used that there had been 

 an increase of rain until I860, and after that year a. steady 

 decrease. 



2d. "Does the rainfall of New York still diminish, will it 

 continue to do so, and does this variation occur in the early 

 or latter portion of the year?" 



By the observations used it appears that the rainfall of the 

 city will most probably continue to decrease by fluctuations 

 for several years to come, and that the variations are nearly 

 the same in the two portions of the year. 



