The Power And Effect Of Machinery

Dr. Lardner has done a great deal towards familiarizing Science with the inníses. He excels in clearness of definition, and is peculiarly happy and striking in Uustration. A single one ofhis illustracions wil! at times fill the mind ivilh a volume of ideas. A few exnmsles from his Lectureon the Steam Eny'ne are exactly in point. A pint of water, evaporated by two iunces of coal, swells into two hundred ind sixteen gallons of steam, with a me:hanical force sufficient to raise a weight Df thirty-seven tonsa füot high. By allowingit to expand, by virtue of its elasticity, a further mechanical force may be attained, at least equal in amount to the former. Five pints of water evaporated by a pound of coke in a locomotivo engine will exert a mechanical power sufficient to draw two tons weight on a railway a distance of one mile in two minutes. - Four horses in a stage coach on a common road will draw the same waight the same distance, in about eight minutes. Four tons of coke, worth twenty-five dollars, will evapórate water enough to carry on a railway, a train of coaches weighing about eight y tons, and transport ing two hundred and forty passengers with their luggage, from Liverpool toBirmingham nnd back ngain, a total distanco of 190 miles, in four hours and a uarter, ench way. To transport the ïame nuinber of passengersdaily by stage :oaches on a comtnon rond, betweon the same place, would requiie twenty coachs and an establishment of three thousand eight hiindred horses, with which :he journey in eaeh direction would be performod in about twelVe hours. A more striking illustratión of the incalculable saving in time and money proiuced by sieam, cannot be given. If the earth were begirt with an i ron railwoy,lhe whole twenty-fjve thousand miles of circuit eould be performed by such a train as that above carrying 240 passengers, in five weeks, with thirty tons nf coke, costing not quite one hundred and ninety dolllirs.' A bushei of coils as used íd Cornwall will raiso fifty thousand lons of water ane foot high. The work of a stage horse is equivalent to about five hundred tons raised n foot. "A bushei of coals, consequently, as used in Cornwall, per. formsas much laboras a day's work of ane hundred such borses." Thö materials of the gteat pyramid of Sgvp?, s'andingon a base measuring seven hundid feet each way, and five hundred feet in height, weighing twelvesand, seven hundred and sixty millions of pounds, and which requirect for its con construction, the constant labor fortwenty years of one hundred thousand men, would bo raised from the ground to their present position by the combustión of