Polytechnic Association. 853 



saturated to any desirable degree by the coal tar. The shingles are 

 then placed in a dry-house and the volatile and inflammable elements 

 of the coal tar evaporated therefrom. They are then surfaced or 

 " veneered " with a coat of coal tar pitch from which the volatile and 

 inflammable elements have been entirely removed by distillation. If 

 desirable, in the process of surfacing or " veneering" the shingle with 

 coal tar pitch, a stone finish may be applied at a very slight cost. By 

 the process of saturating the wood with coal tar and then evaporating 

 its volatile and inflammable elements, we have actually a diffusion of 

 coal tar pitch, which is one of the most uninflammable, tenacious 

 cements known, diffused through the grain of the wood. ' As a result 

 of this we have a fire and water-proof shingle, much stronger than 

 the ordinary wood one, that can be afforded at a much less price. 

 Good pine shingles are now selling all over the country at from 

 five and one-half to seven dollars per thousand. The first cost of this 

 improved form of shingle, prepared in the manner described, is from 

 one and one-half to two dollars per thousand. The company manufac- 

 turing the article (like the sample) deliver the same at the depot of 

 shipment for four dollars per/ thousand. In more favorable localities 

 they could be afforded for three, and sold in the retail trade at a 

 cost not exceeding four dollars per thousand. 



Manufacture of Steel and Malleable Ikon 

 By Virgil W. Blanchard, M. D. 



I do not claim the introduction of any new principle in the process 

 of the reduction of cast-iron to malleable iron and steel. 



I do, however, claim to have simplified the " air blast," or pneu- 

 matic principle, so as, first, to be able to produce a homogeneous pro- 

 duct. Second, to remove any per centum of carbon from the metal 

 that may be desirable, and therein to have so simplified and cheapened 

 the process as to put it within the reach of every manufacturing inte- 

 rest in the country. In the practical application of this invention, a 

 stream of molten iron direct from the blast furnace is carried to the 

 converting vessel. By means of a gauge the stream is rendered uni- 

 form in size. 



The converting vessel is simply a cylindrical* vessel, lined with fire- 

 brick and provided with an aperture for the entrance of the stream of 

 molten metal, and another just beneath it for the entrance of the hot- 

 air blast. 



These two apertures enter the vessel about two feet above its bot- 

 tom, the vessel being about ten feet in height. At the lowest point, 



