TROCEEDINGS OF THE POLYTECnNIC ASSOCIATION. 707 



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cUpped-drum, driven by a steam-engine on the boat, the rope is 

 raised and the boat is drawn underneath the rope. The pecu- 

 liarity of the clipped drum is a combination of toggle-joints on its 

 periphery, so arranged that the rope in passing over these joints 

 is pinched with such force as to draw the boat onward. By the 

 revolntion of the drum the joint passes beyond the rope and again 

 opens l)y its own gravit}'; it thus acts like a series of hands 

 grasping, one after the other, the same rope. The advantage of 

 this arrangement is that the whole power is applied to the pro- 

 pulsion of the boat without the loss by slip which occurs when 

 the paddle-wheel or propeller is applied to water. Only one rope 

 is required, for when two boats moving in opposite directions meet, 

 one boat is released from the rope until the other passes, when the 

 rope is again grasped. 



The Solar Focus as a Medical Agent. 

 Mr. Augustus Barnes, of Connecticut, has discovered that the 

 solar focus is a most efficient and admirable caustic. He uses a 

 lens of two or three inches in diameter and pushes the condensed 

 rays over the whole object, to be removed, if not more than two or 

 three inches in diameter, atone sitting. The rays are applied to a 

 very minute point, and changed at each instant, so that the pain 

 is less than might be apprehended. Patients submit to it very 

 readily, without the use of anaesthetics. Dr. Pinkney "W. Ells- 

 worth, of Hartford, descril^es in The Medical and Sutrfical Ue- 

 pjorter the application of the new remedy to a gentleman who had 

 a noevus on the face, extending from the eye to below the mouth, 

 and covering four or five square inches of surface. The rays were 

 condensed with excellent success, even on the very edge of the 

 lower lid of the eye. After two applications, the deep cherry-red 

 color of the skin, and knolis of condensed tissue, an eighth of an 

 inch high, had nearly disappeared; some portions being abso- 

 lutely like normal skin. Lupus, icth3'osis and small tumors have 

 been subjected to this process with promising results. 



How TO Prepake Coffee. 



From Liebig's researches it appears that the oxygen of the air 

 influences the liquid coffee made by pouring boiling water on the 

 roasted and ground berry, so that, although excellent at first, it 

 soon becomes unfit to drink. To obtain the best results Liebig 

 recommends that the good grains of coffee be picked out of a heap 



