Proceebings of the Polytechnic' Association. 861 



an opposite direction and again opened the damper. The pendulum, 

 operating too quickly, produced an alternate closing and opening of 

 the damper until, after a brief period, the pendulum was brought to 

 exactly the right position, and the proper quantity of air was 

 admitted to keep the stove at the required temperature. This 

 apparatus illustrated the condition that will occur in the movement 

 of any very sensitive self-regulating apparatus. 



After further discussion of this subject the association adjourned. 



November 12, 1868. 



Professor S. D. Tillman, Chairman ; Mr. C. E. Emery, Secretary. 

 The meeting was opened by the chairman, who read a number of 

 scientific items, which have been misplaced, and cannot be obtained 

 for this report of this meeting. 



Railway Tkacks. 



Mr. J. II. Jenkins exhibited two models of his improved form of 

 rails, and presented the following paper, describing their advantages, 

 which was read by T. D. Stetson, Esq. : 



" These models illustrate improved methods of constructing railway 

 tracks for steam travel. In one we represent the treatment of the T 

 rail now in common use. Instead of the rails being set singly, and 

 alone bridging from tie to tie, there are introduced on either side of 

 the same, continuous lines of chairs or brackets. These are made of 

 wrought iron or steel, and of the same length as the rails, and are 

 rolled with a groove to fit the sides of the lower half, or webb, of the 

 same. Fitting the outlines of the rail by curves and angles, they set 

 underneath in order to give a uniform support thereto, and, in the 

 aggregate, yield as much, or more bearing surface to the tie as equals 

 the original breadth of the webb of the rail. 



Close by the edges of the brackets, and setting upon the faces of 

 the ties, are placed strong " knees " or " dogs,"'made of cast or wrought 

 iron. These keep the brackets well up to the webb of the rails, and, 

 by overcapping them sufiiciently, bind the whole structure firmly .and 

 securely to the ties by means of strong bolt screws. These screws 

 are made expressly for the purpose. In the outer half of the dogs, 

 the part wliich sets upon the face of the tie, an oblong hole or " slot " 

 is made to receive the screw. The screws pass through the knees or 

 dogs and are so constructed — having a coarse, shai-p thread, and being 



