182 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



length of axis of twenty inches ; the lower whistle is of the 

 same diameter, but of a length of axis of fourteen inches. The 

 note of the shorter bell is a fifth of that of the longer. This 

 arrangement gives a melodious sound, unlike that of ordi- 

 nary locomotive whistles, and on that account has extraordi- 

 nary merit; its character being strongly distinct from that 

 of steamboat whistles. In reference to the audibility of 

 signals in different kinds of weather, it was found that a 

 sound moving against the wind, and inaudible to the ear on 

 the deck of a schooner, was heard by ascending to the mast- 

 head. In general, it was stated that when the fishermen in 

 the morning, on the Banks of Newfoundland, hear the sound 

 of the surf to the leeward, or from a point toward which the 

 wind is blowing, they take this as an inevitable indication 

 that in the course of from one to five hours the wind will 

 change to the opposite direction from that in which it is 

 blowing at the time. General Duane states that the fog- 

 signals at Cape Elizabeth, and at Portland Head, which are 

 respectively nine and four miles southeast of Portland, can be 

 heard in the latter city much better during a heavy northeast 

 snow-storm than at any other time, although the sound comes 

 to the city in nearly direct opposition to the course of the 

 wind. The most perplexing difficulty, however, arises from 

 the fact that the signal often seems to be surrounded by a 

 belt in which the sound is entirely inaudible. Thus, in mov- 

 ing directly from the station, the sound is audible for the 

 distance of a mile, is then lost for about the same distance, 

 after which it is again distinctly heard for a long time. This 

 action is common to all sound signals, and has been at times 

 observed at all the stations; even at one where the signal is 

 situated on the bare rock, twenty miles from the mainland, 

 with no surrounding objects to affect the sound. Rep. Light- 

 house Board, 1874, Appendix. 



OX CELESTIAL PHOTOMETRY. 



Professor Thury communicates to the Physical Society of 

 Geneva a very full description of a new photometer adapted 

 to astronomical purposes, and also some general considera- 

 tions upon photometry. It is not at present necessary, as it 

 was fifty years ago, to insist upon the importance of photomet- 

 ric observations in astronomy. We know that the problems 



