712 PHILOSOPHICAL TKANSACTIONS. [aNNO J 763. 



ance, is by this method reduced to 2 lb. lOoz.; and if there were any need of 

 reducing it further, it might be done by applying two small quadrants to each 

 pivot of the larger, which would reduce it to 1 oz. or less. 



It is not easy to determine the quantity of friction that was in the plug frame: 

 but that has also been reduced to -^ by the application of sevefal rollers 5 inches 

 diameter, whose pivots are ^ inch diameter, on which it now moves. But it is 

 evident that a power = 440-|- has been saved by changing the position of the 

 axis of the lever; and a power of 421 lb. 6 oz. by reducing the quantity of 

 friction in the pivots. 



The visible effect, with respect to the working of the engine, according to the 

 most exact observations by different persons, both before and after these several 

 alterations were made, is that it now makes 18 strokes at 8 feet per stroke, for 

 15 that it ever made, with the same, or rather a smaller quantity of fuel; and 

 must therefore discharge ^ more water in equal time; which consequently saves 

 4 of the fuel. But the effect is found still greater, as to supplying the tenants 

 with water; for the engine performs the same service better now in 5 hours than 

 ever it did before in 6; which can only be accounted for by the extraordinary 

 regularity of its stroke, which does not abate of its full length suddenly, as it 

 used to do when the strength of the fire abated : this Mr. F. takes to be occa- 

 sioned in a great measure from placing the axis above the lever, by which the 

 centre of gravity, becomes reversed to what it was before ; so that it requires the 

 same power to keep the end of the lever depressed as low as the springs, that it 

 required before to bring it back, when so much depressed; which is a particular 

 benefit ; for the stop or set, generally in large engines, when the ends of the 

 lever come to the springs, is a defect that has been endeavoured to be remedied 

 in some degree by the help of the springs. But when the axis is placed above 

 the lever, and the friction reduced, as above, if one end is brought down to the 

 springs, and let to return, it carries the other end down to the springs without 

 any resistance, and will continue to do so several times, abating somewhat of 

 the length of the stroke each time. 



This engine, from several improvements that have been made in the boiler, 

 consumes but 4 bushels of coals in an hour ; which is deemed -f less than others 

 of equal size; and it performs the same work now in 20 hours that it did before 

 in 24 hours, which is a saving in effect of l6 bushels in 24 hours, amounting to 

 162 chaldrons in a year's constant work ; which is a very considerable article, 

 even where coals are to be had at a cheap price. 



