394 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



first, cuts off this opposing action of the wires at the opposite 

 halves of the helix ; second, causes the core to become itself 

 magnetized ; and thirdly, by this magnetism induces a magnet- 

 ism of the opposite kind in the outer tube, which is added to 

 the magnetism induced by the coil. A magnet, therefore, of this 

 form will be peculiarly sensitive to weak currents, and will 

 enable us with the same battery to telegraph to a greater dis- 

 tance. 



Mr. Johnson had made a horse-shoe magnet, with the ends 

 turned inward, so as to point exactly opposite to their usual 

 direction, bringing the keeper entirely inside of the magnet, and 

 winding it to the poles, in the usual way. He had found it much 

 stronger than the same wire would have been if the magnet 

 had been in the ordinary horse-shoe form. This tended to cor- 

 roborate Dr. Vanderweyde's theory. 



REFRIGERATION. 



The Chairman said that it was desirable that there should be 

 an examination of the different refrigerators now in use, and 

 especially for the purpose of ascertaining what is the importance 

 of circulating a current of air within the provision chamber of 

 a refrigerator. He had observed that in those refrigerators 

 Avhich have a circulating current of air, however small, the con- 

 tents would be found free from any disagreeable odor ; while in 

 others, kept entirely closed, and the air kept still, there would 

 soon be a disagreeable odor, even while the contents of the 

 refrigerator remained substantially sound. 



SAWING SHIP TIMBER. 



Mr. Haskell presented the following report : 



Report of the committee of the Polytechnic Association of the 

 American Institute, appointed to examine the sawing machine 

 of Mr. H. S. Vroomau. 



The committee have examined the machine, and seen it at 

 work; and have also examined the records of patents, to find 

 what had been done before in machines of this kind ; and have 

 come to the conclusion that Mr. Vrooman's invention is the only 

 one that automatically saws the shapes required for ship build- 

 ing, and other work in which compound curves are required ; and 

 that it is a highly useful machine, and as simple in construction 

 as could be expected, considering what it accomplishes. 



