S46 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



greater pressure on a than b, and when the direction is from a to B, then 

 the diagonal a b represents direction of the forces, and the pressure is 

 greatest at the point b. When the brake is applied sufficiently strong to 

 cause a reversal, it is evident if the truck-wheels are both of the same size 

 and weight, that the wheel which would reverse must sustain the least 

 weight, or, in other words, be held to the track by the least friction.-— 

 Therefore, in the direction n, the wheel at B would reverse, and in the direc- 

 tion b, the wheel at a would reverse. This brake was found to be useless 

 in practice on account of its violent action, but it illustrates verj'^ aptly the 

 change in the distribution of force with each change of direction. 



Oil Wells. 



Mr. Overton said he had just returned from the oil region of Pennsyl- 

 vania, and among the various contrivances used there for raising the oil, 

 one was novel to him. It consisted of a small iron tube which is passed 

 down the wells beside another larger tube, and has its lower end bent up 

 and inserted in the open end of the large tube, leaving a space between the 

 tubes. Air is forced down the small tube, and rises into the large tube, 

 the end of which is in the oil. As it rises, it carries with it to the surface 

 the oil or water. This contrivance was being extensively used; he would be 

 glad to know whether it w^as a practical and economical plan. 



The Chairman said there was a great loss of power in this apparatus; 

 first, in the power required to condense the air so as to overcome the pres' 

 sure, increasing with every 80 feet in descent about 16 lbs., this loss is 

 principally by friction ; second, in the use of this compressed air on the 

 principle of exciting' motion by parallel currents. Numerous experiments 

 on record show how much power is wasted by this application of this prin- 

 ciple of parallel currents. There may be cases where the contrivance 

 spoken of would be convenient ; and if the cost of power was small, con- 

 venience might be consulted. 



Mr. Bartlett agreed with the chairman in the opinion that there was a 

 a loss of power in this blowing apparatus. 



Mr. Parmalee said that beside the ordinar^^ pump, he has noticed in his 

 visit to the oil region, a kind of bucket about five feet long, which was 

 used to raise oil in wells wlien the flow was slov/ and never quite to the 

 surface. 



Mr. Overton stated that on the first opening of some of the wells the 

 flow of gas was very violent; in some cases the water around the surface 

 was frozen by the rapid absorption of heat by the liberated gas. Another 

 singular phenomenon is the reverse of this: the suction sometimes is vio- 

 lently downwards. 



Mr. Garvey was not disposed to believe that the action of the oil wells 

 was due entirely to gas. The same principle that produced the flow of 

 water in the artesian well must operate here. The pressure of gas must 

 be immense to raise water to the height described. 



The time for adjournment having arrived, it was agreed to select the 

 subject of "Petroleum Wells" for the next discussion. Adjourned. 



