VOL. XXXIV.] 



PHILOSOPHICAL TRANSACTIONS. 



137 



From Long. 68 Deg. to 81, is in Hudson's Straits, where is the greatest Variation, and the Compass 

 will hardly Traverse. 



An Account of several Experiments concerning the Running of Water in Pipes, 

 as it is retarded by Friction and intermixed Air: some of which were 7nade 

 before the Royal Society. With a Description of a new Machine, by which 

 Pipes may be cleared of Air, as the Water runs along, without Stand-Pipes, 

 or the Help of any Hand. By the Rev. J. T. Desaguliers, LL. D. F. R. S. 

 N° 393, p. 77. 



Having found by several experiments in small, that through a long pipe, 

 water would not be discharged in the same quantity, by a great deal, as il 

 would be through a shorter of the same bore, the orifice being at the same 

 depth under the surface of the water in a reservoir. Dr. D. made an experi- 

 ment on a pipe above 1000 yards in length, and of H inch bore; and found 

 that the quantity of water given was much less (he thinks 44- less) than it 

 ought to have been according to Mons. Mariotte's rules; and that something 

 more than the friction, on account of the length of the pipe, had retarded 

 the water ; which he since found to be air confined in the eminent parts 

 of the pipe. A ftill account of this experiment the Dr. published in his 

 Notes on Mariotte's Mouvement des Eaux, in the English translation, some 

 years since. 



Considering this matter again lately, the Dr. made tlie following experiment. 

 In fig. 3, pi. 3, A is a vessel containing a cubic foot in the inside, and kept 

 always full by means of the pipe b running from a larger vessel. CD is a short 

 pipe, of \ of an inch bore, 2 feet in length, opening into the bottom of the 

 cistern a, and whose orifice d is always 10 inches below the bottom of a. 

 And OGEEEHF is another pipe, of the same bore, whose orifice f is likewise 10 

 inches below the bottom of a. This pipe is 113 yards long, lying along the 



VOL. VII. T 



