68 ANNUAL OF SCIENTIFIC DISCOVERY. 



film of water between the iron of the boiler and the scale, and 

 the latter is loosened and broken np by the expansion of the 

 watery film into steam. By exalting the intensity of magnetic 

 action, by the substitution of a powerful electro-magnet in place 

 of the weaker permanent magnets commonly used, the effects of 

 deposition an(i removal of scale take place with such increased 

 rapidity as to produce in a few hours, results which, with the 

 ordinary apparatus, have required many weeks or months." 



The introduction of metals in the water of the boiler, which are 

 electro-negative or electro-positive, to the metal in the shell (co])- 

 per or zinc), either tends to corrode the boiler, or to oppose the 

 action of the instruments. In the whole course of the experi- 

 ments there was no evidence of the production of any galvanic 

 action having the slightest tendency to oxidize or in any way 

 injure the metal of the boiler. 



PARAFFINE AS A LUBRICATOR. 



The oils and lubricators at present used on machinery at high 

 temperatures are decomposed by heat, and leave a residual cotit- 

 ing, more or less thick and viscid, the adhesion of which to the 

 sides of the cylinder interferes considerably with the free move- 

 ment of the piston. In fact, it is impossible to attain the full limit 

 of power in hot-air engines, like those of Ericsson and others, 

 because it is impossible to lubricate them, and to prevent the ad- 

 hesion of the moving parts. M. Monet, in " Cosmos," advises the 

 use of mklhie (CsoHeo), a substance obtained from the paraf- 

 fines, insoluble in water, soluble in the fixed oils, volatile without 

 decomposition, not boiling under 370° F.,^ of the consistency of 

 wax at ordinary temperatures, and floating on the surface of cold 

 water. It is cheap enough to be employed on the large scale, 

 and preserves from oxidation and adhesion. 



PETROLEUM FUEL FOR STEAM SHIPS. 



According to the " American Artisan," the absolute theoretical 

 evaporative powers of a pound of anthracite and a pound of 

 petroleum stand respectively at 12 and 22 lbs. of water. The 

 average cost of crude petroleum is about 21 cents a gallon, and 

 of coal 5 dollars a ton ; in other words, the petroleum costs 3 

 cents per lb., while the cost of coal is between the fourth and 

 fifth of a cent per lb. ; hence the petroleum costs 13 times as 

 much as the coal, and, its absolute heating power considered, its 

 heat costs 7 times as much as the heat from coal, and it costs con- 

 siderably more than this in its practical application. The cost of 

 the apparatus for using petroleum is great, and its durabiht}'' 

 small ; some economy wouhl result in the cost of attendance on 

 the fires, but the other disadvantages named are decisive against 

 its economical use as a steam fuel. Moreover, extraordinary ^are 

 in storing and using this fuel must be constantly exercised. Under 



