898 Transactions of the American Institute. 



December 17, 1868. 



Professors. D. Tillman in the chair; Mr. C. E. Emert, Secretary. 

 New Petroleum Lamp. 



Mr. John Johnson, of Saco, Maine, exhibited a lamp which he 

 claimed to be non-explosive. The tube in which the wick is held 

 passes to the bottom of the oil ; the oil cannot be taken out 

 without putting in an equivalent of air. Any lamp could be made 

 non-explosive if constructed on this principle. This lamp cannot be 

 exploded, as all the air to form an explosion has to pass beneath the 

 liquid or oil. Fire cannot pass through the oil, and the air in an 

 explosive mixture is not saturated with the vapor of the oil. 



Dr. D. D. Parmelee said it. is the admixture of good petroleum 

 with the cheaper products of petroleum, for which there is no sale, 

 that makes the kerosene lamps so dangerous. If the oil is of the 

 proper standard there is no more fear of a petroleum lamp bursting 

 than of a common oil lamp. 



The Tempering of Steel. 



Dr. L. Bradley said that at a late meeting Mr. Wiard said that the 

 liardening.: of steel depended on the condition of the molecules, and 

 in order that steel should be made perfectly hard and brittle, the 

 molecules must be cooled one after another, and the piece be plunged 

 into the water endwise. He, the doctor, had tried .some experiments 

 in this line. This piece of steel was hardened in the usual way, and 

 it is very hard. The other specimen was cooled with two wet sponges, 

 which is also very hard. Another piece of steel he heated to a cherry- 

 red, and it is not quite as hard as the others, and can be bent. 



Propulsion OF Vessels. i 



Mr. Thomas D. Stetson, in alluding to a late discussion, said devices 

 for propelling vessels appeared thousands of years ago, and new 

 plans are still appearing. The paddle-wheel system dates after 

 the sucking pump. Of contrivances for propelling vessels there were 

 patented in. 1865, fifteen ; in 1864, ten ; in 1863, thirteen ; in 

 1862, eight ; in 1861, eight ; in 1857, six ; in 1855, sixteen ; in 

 1854, ten. Thus 217 inventions have been patented in this country, 

 and taking those that were not patented would make some 400. 

 There is no subject that involves more profound mathematics than 

 that of propulsion. By using a large paddle-wheel we get the 



