36 REPORT— 1870. 



By turning "on" a "strike -silent" stop, a hammer lever is brought into 

 connexion with the escapement, and strikes a ball at every contact ; the observer 

 has therefore notliing to do in noting intei-val or hourly velocities but to notice the 

 seconds' hand of his watch or chronometer (a split-seconds or chronograph would 

 be preferred), while he counts the number of times the bell is struck, each 

 of which corresponds to the -j^g mile, and, by formulre arranged and explained by 

 Mr. Hall (who has also arranged a comprehensive series of tables for use with the 

 instrument) the houi'ly velocity may be readily deduced. 



The following formula has been arranged for deducing the hourly velocity of the 

 wind from observations during intervals of minutes and seconds. 



Let T be the interval of observation in minutes and seconds, expressed decimally, 

 60 constant (min. = l hour), and .r the quantity required, which will represent tlie 

 number of times T is contained in one hour, -05 unit of distance, b number of beats 

 on bell, x as before, and V velocity required; then 



GO 

 ^= T- = 

 .*. -Oo X b X X = Y, 

 Supposing, therefore, the bell is struck 15 times in 1 min. .30 sec, expressed deci- 

 mally I'.SO min. ; then 



.r=,-^=40 : .*. •05x15x40=3000 miles. 



By noticing the exact seconds upon which the first and last beat are struck, the 

 results will be as accurate as if the instrument 2vere capable of rccorcUnc/ the one- 

 thousandth part of a mile, while the battery is less called into action. 



In noting velocities extending over long periods of time, the instrument is read 

 in the same manner as the ordinary cup-and-dial anemometer. 



This paper, which was of considerable length, was illustrated by tlie Electrical 

 Anemometer (by Messrs Negretti and Zambra, under IMr. Hall's directions) and 

 mechanical diagrams. 



On the Rainfall of tlie United States. By Professor J. Henry. 



Heat, Light. 



Queries respecting JEthcr. By Charles Brooke, M.A., F.Ii.S. 



When light and caloric were supposed to consist of material molecules, the 

 hypothesis of tlio universal existence of a transmitting medium was unnecessary, 

 since particles of matter might with the utmost freedom be projected through vacu- 

 ous space ; but as light and heat are now generally admitted to consist not of trans- 

 mitted matter, but of transmitted vibratory motion (and why may not electricity', so 

 freely interchangeable with the former, be admitted into the same category ?), the 

 necessity of the existence of a highly elastic and attenuated transmitting medium, 

 pervading infinite space, becomes at once apparent; and this medium, hitherto not 

 cognizable to our senses, has been termed " a3ther." But it has been further assumed 

 that (ether is alone capable of transmitting the extremely rapid vibrations of light 

 and heat, and that it must therefore necessarily pervade or permeate all kinds of 

 sensible matter. The questions proposed to be raised in this communication are 

 the necessity of this interstitial hypothesis, and the probable capability of ordinary 

 matter to transmit the vibrations of light and heat. 



It is now generally admitted that when a body becomes heated, its own particles, 

 and not merely those of the supposed interstitial rether, are thrown into a state of 

 vibratorj' motion, the amount of heat corresponding probably to the amplitude of 

 the vibrations ; hence a certain amount of energy has been communicated to those , 

 particles, and (at all events, in the case of celestial radiations) the molecules of ' 

 aether must previously have possessed the energy or vis viva which they have com- 



