MKCHANICS AND USEFUL ARTS. G9 



tlip«o circumstances tliere docs not seem to Ik; the sliirhtcst proba- 

 bility that petroleum at present can take tlie place of co.il as a 

 steam fuel. 



LIQUID FUEL. 



At the Annual Meeting of the " London Institution of Naval 

 Architects," in 1868, Capt. Selwyn read a paper on " Liquid Fuel," 

 by the use of which, instead of coal, a ship could, with the same 

 weight of fuel, be supplied for a voyage of 3 weeks under steam 

 instead of 1, with less expense for fuel and more room for 

 freight. 



lie spoke particularly of the fluid generally known by the name 

 of creosote, the price of which is at jDresent three-quarters of a pin- 

 ny per gallon, or 13s. 9d. per ton. From its specitle gravity being 

 greater than that of sea-water, in case of fire from any cause the 

 fuel might be run into the bilge-water in the hold or into the sea. 

 Being not inflammai)le under 240° F., there is no danger of explo- 

 sion, and it is not lialjle, like coal, to spontaneous combustion. 

 Great economy is said to be the result of the use of this fuel. 



TESTING STEAM BOILEPtS. 



Prof. S. "NV. Robinson, of the University of Michigan, commu- 

 nicates an article to the "Journal of the Franklin Institute" for 

 January, 1868, as follows: " It is generally believed that steam 

 boilers become weakened, for resistance to internal pressure, after 

 continued use, fi'om various known and unknown causes; so that 

 the engineer cannot judge of the pressure to which his boiler can 

 be worked with safety. But this he may determine by a very 

 simple process, and means which are alwaj's at command. It is 

 as follows : Let the boiler be filled entirely full of cold water, 

 even to the throttle and safety-valves, and all closed tight to pre- 

 vent any escape. Now, by lighting a fire under the boiler, the 

 v»'ater will be gradual!}^ expanded, and produce a pressure suffi- 

 cient even to rupture the iron before the temperature of the water 

 arrives at the boiling-point. While the pressure is increasing, let 

 the steam gauge or pressure indicator be watched; and when the 

 test pressure, which may be twice or more times as great as the 

 working pressure, is leached, a portion of the water may be al- 

 lowed to escape and the pressure reduced. The pressure rasults 

 from the fact that water is expanded more by heat than iron. The 

 process above given is attended with as much safety as the use of 

 the hydrostatic press, unless the water be heated above 212'^, 

 which would not be required unless the boiler leaks. Below this 

 temperature no disastrous consequences would follow, even if the 

 boiler should be torn asunder, inasmuch as explosions result from 

 the sudden expansion of gases or vapors." , . 



