122 MEETING OP THE BRITISH ASSOCIATION 



uver the latter, the column of air within produced a sound, which 

 increased or diminished according to the distance between them. 

 With two tubes, one placed horizontally, the other perpendicularly, 

 a curious phenomenon was observed : when the tuning fork was 

 put in vibration in a certain position between the two unclosed ends 

 of the tubes, no effect was observed ; but when this position was 

 changed, or the mouth of one of the tubes closed, a very audible 

 sound was produced. With a tube of fourteen inches long, open at 

 either end, tones were only obtained by stopping a small hole in the 

 centre ; but on inserting into this a glass tube of three inches in 

 length, the effect was reversed, the sound being only heard when the 

 glass was unclosed : upon increasing this small tube to seven inches, 

 being half the lengh of the larger one, no sound was produced. Mr. 

 Adams said he would not attempt to explain the cause of these phe- 

 nomena, but leave it to Professor V/heatstone and other abler 

 hands. 



Thursday. — Mr. Peacock read a communication from Mr. Tal- 

 bot on the Integral Calculus. 



Dr. Apjohn then read a paper on the use of the Wet-bulb Ther- 

 mometer in determining the specific heat of Air. 



The Rev. Mr. Scoresby gave an account of two very delicate 

 magnetic instruments. The first of these he called a magnetimeter, 

 from its extreme delicacy in detecting and measuring exceedingly mi- 

 nute magnetic influences. The second instrument was a very pow- 

 erful, yet very light, magnet, mounted in such a manner as to be 

 eminently fitted for observing accurately the variation of the nee- 

 dle, as well as its diurnal and annual changes. 



Professor Forbes, in a communication on the Terrestrial Mag- 

 netic Intensity at various heights, has gone far to determine an im- 

 portant but disputed question in Physics, viz. the change in mag- 

 netic intensity at different altitudes above the earth's surface. He 

 stated, briefly, the results of forty-five series of observations with 

 Causteen's intensity needles at 13 stations in the Alps and Py- 

 renees, from six to one thousand feet above the level of the sea, and 

 compared with the intensities observed in the intermediate valleys. 

 The general result at which he arrives is, that there is no general 

 decisive indication of diminished intensity with height, at least 

 within the limits of error of the instrument, and certainly, if it ex- 

 ists, the diminution must be considerably smaller than 31. Kupp- 

 fer has supposed. 



A paper, by Sir D. Brewster on the action or christallyzed sur- 

 faces, was read, and gave rise to some discussion on the part of Sir 

 W. Hamilton and Mr. M'Culloch, but the statements of the paper 

 do not admit of abridgment. 



Dr. C. Williams gave an account of an improved ear-trumpet, by 

 which soupds are rendered audible at three times the usual distance. 



Evening Sitting. — Mr. G. Hall read a paper on the Connection 

 of the Weather with the Tide, and observed that the barometer un- 

 dulates at the changes of the moon, but more commonly sinks than 



