636 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



by one of Telford's assistants, that within twenty miles of London a paved 

 road would be cheaper than one of broken stones. The cost of repairs of 

 a McAdam road in London was proved greater than that of paving in the 

 ^proportion of one hundred to twelve. The only advantage of the broken- 

 stone road is that the horse has a better foothold than on the pavements. 

 The horse is the dictator; he must have a road that makes eight times 

 more detritus than a pavement makes, and, taking all weather together, 

 has about double the resistance. 



The modern road material, iron, is yet to come into general use. The 

 railway has shown its superiority, and the locomotive has shown that the 

 horse is not a necessity. Cast iron for flat roads is the material that the 

 last eighty years has developed; when we have the independent judgment 

 to use it we shall have better roads than the ancient Romans had. 



At the conclusion of Mr. Fisher's remarks, the evening was so far spent 

 that no attempt was made to present the elevated railroad plan. 



Dr. Parmelee said the principal objection made to the underground road 

 was the necessity of breathing bad air — this, coming from those who are 

 constantly visiting badly ventilated assembly rooms, and imderground 

 restaurants, where thousands take their meals by gaslight, does not have 

 the force of sincerity; but to relieve the fears of these gentlemen he would 

 state that it takes only twenty pounds of caustic lime to absoi'b thirty 

 pounds of carbonic acid gas. 



Mr. Thomas C. Smith remarked, if we are compelled now, sometimes, to 

 breathe bad air in our buildings, it was no reason why we should continue 

 to construct badly ventilated apartments. People generally are averse to 

 riding underground. He well remembered the sensation he experienced 

 while passing through the railroad tunnel under the Jura mountain, which 

 is about three and a half miles long. Those who were with him also com- 

 plained of the closeness and dampness of the air — the depressing effect was 

 very general. 



Mr. Nash expressed his opinion at length against the feasibility of tun- 

 nels, and the argument that they were used in Europe would be the last 

 one which would have weight with him. He contended that the light of 

 day was essential to health, and when the effect of these continual dark 

 transits are understood, Americans will refuse to make them. 



The subject selected for the next discussion is "The Utilizing of Waste 

 Products." Adjourned. 



American Institute Polytechnic Association, ) 

 April 14, 1864. ) 



Chairman, Prof. S. D. Tillman; Secretary, Mr. B. Garvey, 



A Caloric Engine. 



Mr. Roper, of Boston, explained, with the aid of diagrams, a caloric 

 engine now in operation at the Sanitary Fair, designed to be used whero 

 email power is required. Its peculiarity is that it does not use upon the 

 piston common air heated, but only the products of combustion. The air 

 to supply oxygen for the combu.stion of anthracite coal is pumped in; the 

 carlpjn is burned rapidly and completely, under pressure, aad tlie resulting 



