172 MEMORIAL OF JOSEPH HENRY. 



and it is a matter of the most profound regret that it was evei: de- 

 molished. It corresponded in appearance with the building con- 

 taining the Geological lecture-room and the Philadelphian rooms. 

 The main room was equal in size to the two rooms of the Philadel- 

 phian Society, and there was a smaller room in a projection in the 

 rear, which was subdivided into a room of moderate size, and tAvo 

 small ones. The apparatus was placed in glass cases surrounding 

 the main room, the seats occupying the centre. Probably the most 

 interesting things in this room were the little horse-shoe electro- 

 magnet, with which he made some of his most important discove- 

 ries — the little machine which he invented, and which was the first 

 machine moved by electro-magnetism, — and the large electro-magnet, 

 which could support 3,300 pounds, and which was for many years 

 the largest in the world. It could be magnetized, demagnetized, 

 and remagnetized so rapidly that a weight of hundreds of pounds 

 could not detach itself from the grasp of the magnet in the interval 

 of reversing the currents. These things are still preserved in the 

 Scientific School, along with the small glass cylinders, covered with 

 sealing-wax, and the electrical machine prepared after the directions 

 of Franklin. As an illustration of character it may be men- 

 tioned that in the largest room of the projection hung a tradesman's 

 placard, upon which was depicted a folded whip, with the legend: 



"A PLACE FOR EVERYTHING, AND EVERYTHING IN ITS PLACE." 



From his lecture-room to the opposite building, and thence to his 

 house, which was the house now occupied by General Karg6, but 

 then standing on the site of Re-Union Hall, stretched a wire, through 

 which currents of electricity were sent that rang bells and thus con- 

 veyed messages. In his house he also had wire connected with the 

 lightning-rod, and needles inserted in the coils of it, that, like 

 Franklin, he might study the effects of electricity while the storms 

 were raging. The little machine mentioned was simply a small 

 beam of iron, surrounded by a conductor of insulated copper wire 

 and supported by a fulcrum, which was caused to oscillate by the 

 influence of two small stationary upright magnets near its ends. A 

 maker of philosophical apparatus once visited Princeton to sell 

 Professor Henry some of his machines. He showed the person 

 this little machine, and was threatened with a suit for^ "infringe- 

 ment of patent rights ! " 



