60 ANNUAL OF SCIENTIFIC DISCOVERY. 



buildings. Fire-proof paints protect only the exterior of a house, 

 or the part least likely to catch fire ; while, on the other hand, 

 a buildino; constructed after the Hoe plan will be thoroughly free 

 from danger. — American Artisan. 



HEAVY LOCOMOTIVES. 



There are good reasons for believing that as soon as steel rails 

 shall have been generally substituted for iron, thereby permitting 

 of weights of from 7 to 9 tons per engine wheel, a nmch more 

 powerful class of locomotives will be in request. The economy 

 of working the heaviest goods trains is now well understood, 

 and it is only the want of strength in the permanent way that 

 limits the weight and power of -G-coupled engines to the exist- 

 ing standard. Six-coupled engines of a weight of 50 tons or 

 thereabouts, with the weight equally distributed, would require 

 cylinders from 20 to 21 inclies in diameter, for 2 feet stroke and 5 

 feet wheels, and the boiler should not have less than 1,800 square 

 feet of surface, and 30 square feet of fire grate. — Engineering, 



EUROPEAN AND AMERICAN LOCOMOTIVES. 



In England, we see the locomotive engineers, as a general 

 rule, aiming at high speed, as little complication as possible in the 

 parts of the engine, utmost simplicity in all things, perfection of 

 adjustment and workmanship, and high-boiler pressure. Upon 

 this last point we may note that a few years since 50 pounds 

 to the inch was considered high ; now 120 pounds and 130 

 pounds are ordinary pressure, and on the North London line en- 

 gines are being run at 180 pounds. 



France has slow speed and very heavy trains ; her engineers 

 aim at large tractive force, do not spare complication, use large 

 quantities of material, and couple numbers of driving-wheels 

 together, making, for example, 12-wheeled coupled engines, 

 things utterly unknown in England, but at the same time they put 

 light weight on those wheels, not more, in fact, than 10 or 12 

 tons on the axle. The French deserve credit for bavins: devel- 

 oped their engines into a form suitable for their shareholders' 

 ideas of trafllc; that is, a heavy engine at slow speed pulling a 

 long load. One expensive necessity has already been evolved in 

 our own country by the quick running of small trains, namely, 

 the necessity for lading down third and fourth lines of rails to 

 accommodate the traffic, at an enormous expense, which could 

 have been avoided if the trains had been worked as on the Great 

 Northern of France. The fuel for a heavy train is much the same 

 as for a light one, or very little increased ; but in running double 

 sets of trains over double lines of rails, the wages are doubled ; 

 the first cost — that is, line accommodation — is doubled, the num- 

 ber of engines is doubled, while the wear of engines and road is 

 quadrupled. 



