224 Apparent Diminution of Weight in certain circumstances. 



The same apparatus modified a little, becomes a very delicate air 

 thermometer. It is only necessary that atmospheric pressure should 

 be excluded, and that the tube G I should terminate at I in a bulb 

 containing air. If the bulb be partly filled with the vapor of mer- 

 cury, at the time it is sealed, the elasticity of the air within, will be 

 of a low tension, when the instrument becomes cool. In this case 

 the tube AC may be materially shortened, and the iron joint dispen- 

 sed with. The vapor of water, alcohol or ether may be substituted 

 for air, taking the precaution to leave an excess of liquid in the hor- 

 izontal tube or bulb. An instrument of extreme delicacy, may thus 

 be constructed, but whether air or vapor is used, it is rather more 

 difiicult to adapt a scale to it, than a common thermometer. 

 Cincinnati, Ohio, April 8, 1834. 



Art. IV. — Apparent Dimunition of Weight in certain circumstan- 

 ces ;* by W. E. A. Aikin. 



Sir David Brewster, in one of his letters on Natural Magic, ad- 

 dressed to Sir Walter Scott, relates the following " as one of the most 

 remarkable and inexplicable experiments, relative to the strength of 

 the human firame." The experiment was performed in the presence 

 of Sir D. B. by Major H. who had seen it performed at Venice, un- 

 der the direction of an officer of the American Navy. " The heav- 

 iest person in the party lies down upon two chairs, his legs being sup- 

 ported by the one and his back by the other. Four persons, one 

 at each leg and one at each shoulder, then try to raise him, and they 

 find his dead weight to be very great, from the difficulty they expe- 

 rience in supporting him. When he is replaced on the chairs, each 

 of the four persons takes hold of him as before, and the person to be 

 lifted, gives two signals by clapping his hands. At the first signal, 

 he himself and the four lifters begin to draw a long and fall breath, 

 and when the inhalation is completed or the lungs filled, the second 

 signal is given for raising the person from the chairs. To his own 



* Mt. St. Mary's College, Emmitsburg, March 12, 1834. 

 To Prof. Silliman. — Dear Sir — I send you the following as possibly possess- 

 ing sufficient interest to find a place in the Journal of Science ; if so, it is at your 

 service. Respectfully and sincerely, 



your humble and obedient servant, W. E. A. Aikin. 



