AMERICAN INSTITUTE. 497 



vussoirs of the arches in their proper place, and so prevent their beinc 

 lifted by drift timber, &c., in case of a flood. 



On the subject of the Aurora, Mr. Seeley said that elementary books say 

 our atmosphere is 45 miles high, but electric light is s^aid to be seen hun- 

 dreds of miles high ; and as it cannot be seen iu a vacuum, there seems to 

 be strong evidence of the existence of ether, or other matter, beyond our 

 atmosphere. 



Mr. Garvey. — The measurements given at different times of the altitude 

 of the aurora are such rude approximations, and differ so widely, that it is 

 little better than guess-work to undertake the measurement of such an 

 altitude with the data which we can obtain. We assume, for instance, that 

 the radiation of the auroral light is from a "pole" not an "axis," and 

 that the light from the aurora follows the same laws as solar light, both 

 assumptions, of which we have no proof. 



Mr. Seeley considered that the last aurora was well calculated for mea- 

 surement, and saw no difficulty in measuring the altitude of the auroral 

 displays, since the light radiated from a well-defined point. The heights 

 of clouds can readily be measured from the elements furnished by their 

 shadows, in connection with the horizontal and vertical directions determined 

 by plummet.* 



The regular subject of the evening being called up, Mr. Howe read a 

 masterly paper on 



MUSICAL INSTRUMENTS. 



He divided all instruments into two classes ; first, those which produce 

 musical tones by the vibration of a column of air ; second, those which com- 

 municate sound to the surrounding atmosphere by their own vibrations. 

 The organ was taken as the type of the first class, and the violin as that of 

 the second. 



In commenting on organs and other wind instruments, played by means 

 of keys and stops, Mr. Howe paid a well-merited compliment to the im- 

 provers of the Melodeon (Carhart, Needham & Co.), who brought the de- 

 lights of music within the power of possession of the many, and substituted 

 an instrument capable of sustaining its tones for the tinkling of the cheaper 

 kinds of pianos. Brass instruments and drums for martial music were 

 passed in review ; but, in consequeuce of their want of perfect intonation, 

 and the crashing, braying noises which they produce, they were esteemed 

 only fitted for the noise and tumult of war. The flute was then traced 

 from its earliest histor3'^ to the perfect Bcehm flute of the present day, the 

 most finished form of which, as made and improved by Mr. Badger, was 

 then exhibited, and its powers were tested by some performers present. 

 Its compass was considerable, and the fullness of the deep tones was com- 

 mented upon by several. 



• It appears now probable that the aurora is an optical phenomenon, due indeed to electro- 

 magnetism, and that, as in the instance of the rain-bow, no two persons see the same plicnomo- 

 non. Hence ail attempts to estimate its distance would, in this view of the subject, be futile. 



JR. 



[Am. Inst.] 32 " 



