474 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



of sand was thrown up tlirong-li thorn wlicn tlie water comrnencod to boil. 

 The extra expense of th<>se kettles is only thirty cents. 



The Chairman. — AVater is heated liy convection, and not by conduction. 

 We can have ice at the bottom of a boiler, and water csin be made to boil 

 at the top, if the heat is applied at the top. When heat is applied at the 

 bottom, the rarified water and steam rise to the top, displacing the cold 

 water, which descends ; thus the heating- of water is effected by its circu- 

 lation. 



New Link Motion. 



Mr. W. R. Greenleaf, of Silver Creek, N. Y., exhibited a model of his new- 

 mode of producing- link motion for steam engines. Upon a shaft a sleeve 

 is fixed, upon which movable eccentrics are placed, and so arranged that 

 when the engine is running the cut off can be put in any desired position- 

 The ordinary link sometimes slips a quarter of an inch, and this has a very 

 bad effect. In this invention, when it is once shifted, it will remain so. 

 Another improvement in the model was a conical valve, with three narrow 

 ports. The trouble with conical valves has been that they expand before 

 the other parts, but in this plan the heat is on the outside, which prevents 

 the valve from sticking. The motion of this valve is such that it will 

 travel much faster at the end of the stroke than in the middle. The 

 advantages which are claimed for this valve, are that it is a balanced 

 valve, very simple in construction, and it gives a more perfect movement, 

 is not liable to get out of order, and is specially adapted for -locomotives. 



After examining the various models presented during the evening, the 

 Association adjourned. 



"Novelties at the Fair," was continued for the next discussion. 



Adjourned. 



American Institute Polytechnic Association, ' 

 October 16, I860. 

 Chairman, S. D. Tillman, Esij.; Secretary, Mr. John W. Chambers. 



Novelties at the Fair. 



IMPROVED SUSPENSION CULVERT. 



Mr. Charles Mclntire presented for examination his plan, herein described, 

 of the improved suspension culvert. Sewerage near cities and towns has 

 always been a subject of great perplexity, on account of the expense and 

 trouble of procuring a foundation. This has been the difficulty, especially 

 ■when the culvert (or sewer) was required to be constructed through 

 swamps, quicksands, and where it is necessary to be extended out into the 

 river. 



The accompanying engraving represents the improved suspension cul- 

 vert (or sewer) which will obviate this difficulty by dispensing with the 

 coffer dams, cradling, and the trouble of using pumps, so necessary some- 

 times in the old method for obtaining a foundation. The plan is so plainly 

 shown in the engraving that a description is hardly required. A repre- 

 sents the loWi^T arch of iron, with tlie flanges at its upper edges resting 

 upon the stringers c, supported by the piles d d. The masonry arch b 

 rests uDon the flanges of the iron arch A. 



