, F OL TTECENIC ASSO CIA TION Pr CEE DINGS. 615 



its contents, just in proportion to their conductivity, which is 

 directly proportional to the area of the transverse section of the 

 conductor, and to the specific conductivity of the material of which 

 it is composed. Iron is specifically more conductive than water, 

 but the area of the transverse section of the water is so very much 

 greater than that af the shell, that we may assume their conducting 

 power, in the whole, to approximate equality. The whole boiler 

 and its contents, therefore, are continually pervaded by an equal- 

 izing force, sufficiently overwhelming to neutralize and quiet the 

 slight disturbance caused by the evaporation, which had occasioned 

 the accretion; consequently, there is no attraction between the 

 boiler and the earthy matters, and no incrustation. 



Whether there is anything in this hypothesis or not, no matter; 

 the fact is established; and I apprehend that it is only the cropping 

 out of a great principle, which will lead to the development of 

 still more important results. 



From the discussion which followed this paper, it was evident 

 that further proof is required of the efficiency of this method of 

 protecting steam boilers. 



S. H. Maynard, Esq., exhibited specimens of wood pavement, 

 and submitted the following paper, prepared by C. A. Williams,. 

 C. E.: 



WOODEN PA VEMENT8. 



The subject of pavements possesses more than usual interest just 

 at this time, from the fact that an effort is being made to introduce 

 into this and other cities what is believed to be an improvement 

 upon the old plans of stone pavements, viz: improved wooden, 

 pavement. And in order to a full understanding of the design of 

 the plan now presented, a brief comparative review of the features 

 of other plans, in connection with the requii'ements, is indispensable. 



In considering the subjects of improvement, and especially 

 those of an architectural or mechanical character, we must first 

 ascertain the requirements, and then determine upon the best kind 

 and most correct shape of the materials; and which questions can 

 be determined by rules and data well laiown to experts and prac- 

 tical men, so that, although the ingenuity of the inventor may make 

 many combinations in the shapes and positions of materials, it is 

 generally not difficult to determine which is best adapted to the 

 requirements to be kept in view. But it often happens that the 

 hap-hazard inventor, or a random and uninformed delver in the field 

 of invention and improvement, may originate a subject or method 



