184 ANNUAL OF SCIENTIFIC DISCOVERY. 



current must he greater, the longer the interval between the pulses, since the 



rarefactu 



interval. 



rarefaction within the tube will he greater nearly in the ratio of the same 



DOVE S EXPERIMENT IN ACOUSTICS. 



This experiment consists in rendering the tone from a vibrating diapason 

 very distinct, so that it could be heard through a large hall, by causing it to 

 vibrate in a certain relation to a glass flask containing water. The flask 

 should not be filled, and the diapason should not touch it, but be held in the 

 hand in the prolonged neck of the balloon. The sound returned depends on 

 the relation of the two limbs of steel to the neck of the flask. The percep- 

 tion of sound is most distinct when the plane of the two branches is in the 

 axis of the neck, and is null when the plane is perpendicular to the axis. 

 Dove ascertained these facts while engaged in researches as to the question 

 whether the ear, which is for a time sensible to a certain tone, becomes in- 

 sensible to it again, as the eye does to a given color, when it has for some 

 time contemplated it. The eye may be said to habituate itself to certain 

 colors, as the olfactory nerves do to persistent odors. Dove's researches 

 returned an affirmative reply to the point in question. Sflliman's Journal. 



CURIOUS ACOUSTIC EFFECT. 



At a recent meeting of the Royal Institute of Architects, London, Mr. 

 Parris, who renovated the painting in the dome of St. Paul's, said he had 

 remarked, from his experience of that cathedral, that he could be heard dis- 

 tinctly at the distance of two hundred and twenty feet, when he was imme- 

 diately under the eye of the dome. Any person standing on a particular part 

 of the pavement below, at a right angle, or nearly at a right from where his 

 voice would strike the roof, could hear even a whisper with the greatest dis- 

 tinctness ; in fact, he had often held conversations in that way. As he 

 moved to a different part of the dome, the person below Avould have to move 

 to a different position, but in the same angle; but when this became too 

 great, the voice was lost. He had often tried the experiment, and found that 

 the reverberations in a dome were always repeated thirty-two times, exactly 

 corresponding with the points of the compass. It was the same at the 

 Colosseum, London, where he had tried it with the flute, voice, and every 

 means. He had tried experiments in the same way in St. Paul's, upon the 

 level of the organ, and above and beneath it; and he found invariably that 

 the sound was always best heard at the point opposite to where the voice had 

 struck. It was precisely the same with the voice ascending as descending; 

 in fact, his attention had been called to the matter by hearing a man below 

 ask another for sixpence; he exclaimed, "Take care, he is giving you a bad 

 one," and the man immediately turned round, surprised as to where the 

 voice could be coming from. Builder. 



EXPERIMENTS OX THE SUMMIT OF MT. BLANC. 



Some interesting experiments on combustion, sound, etc., recently made 

 on the summit of Mt. Blanc, by Professors Tyndall and Frankland, were de- 

 tailed to the British Association, 1839, as follows: Six candles were chosen 

 at Chamouni, and carefully weighed. All of them were permitted to burn 

 for one hour at the top; and were again weighed when we returned to Cha- 

 mouni. They were afterwards permitted to burn an hour below. Rejecting 



