Peoceedt^'gs of the Polytechnic Association. 10-37 



miles nn hour ; this depth would be 121 feet. The cars could be 

 started by a stationary engine, of sufficient power to give, in the iii'st 

 20U feet, an impulse that would overcome the rolling and atmospheric 

 resistances, and the car would arrive at the next summit at a speed 

 of six or ten miles an hour. This method of throwing the cars, like 

 shuttles, Barlow proposed, but seems not to liave worked out. It is 

 his original idea, so far as it applies to underground railways, and in 

 my opinion it is a good and feasible one. With stations on the street 

 level, the line may dive under all cross streets, sewers, pipes, l)nild- 

 ings, and other obstacles to a common line, and do no harm to any 

 of them, even during the construction ; and the cost of driving sneli 

 a tunnel would be fai* less than the cost of an open cutting, if the 

 interruption to traffic be computed. An average speed of twenty 

 miles an hour is easily practicable on it ; whereas, on the London 

 line the average is less than thirteen miles, and cannot be got up to 

 fourteen without lightening the trains. 



But the highest speed attainable is on iron-floored undergrade 

 streets, with steam carriages that can pass each other and make long 

 runs ; one street being for the down travel, and another for the upward 

 travel, so that collisions if there be any, shall have only the force due 

 t^ the difference of speed. Frecj[uent stops render high average speed 

 impossible ; therefore, railways cannot be the best for city travel. 

 Besides, the flange friction renders the resistance, at high speed, 

 much greater than it would be with plain wheels. 



Mr. 1). W. Bradley read the following paper on 



HOROLOGY IX PAST AGES. 



The field which the speaker proposes to review extends from about 

 700 B. C, to the close of the seventeenth century, and is confined to 

 that branch of horology Mdiicli relates solely to the clock. He has 

 gathered his data from numerous authors, and is especially indubted 

 for numy interesting incidents to AN^ood's " Curiosities of Clcjcks and 

 Watches ;" he is also under obligations for information furnished 'by 

 Mr. Wm. II. Worthen, mechanical draughtsman. 



It is not known at wdiat period our present method of commencing 

 the day at midnight, began. It was doubtless an invention of the 

 ])riesthood, and 1 am not certain that it can be ini|)roved ; although 

 it does eecm odd to call night day. The day actually begins at sun- 

 rise and ends at sunset; and this was the earliest method of reckon- 

 ing. Afterward the day and night were divided into four e(puil 



