POLTTECENIC ASSOCIATION PROCEEDINGS. glQ 



and in localities where other materials could be obtained, would 

 seem to be sufficient evidence that even constructions which are 

 probably not the best, possess advantages over other kinds of pave- 

 ment heretofore used^ and the question of their practicability and 

 advantages being therefore settled by the best evidence — that of 

 actual test — the only question to be decided is the best shape to 

 put the materials into, to meet the requirements heretofore alluded 

 to, and which are well understood. 



Since writing thus far, my attention has been called to the con- 

 dition of one of the experimental pieces of wooden pavement laid 

 in this city, upon one of the plans of construction then referred 

 to — that of small blocks, with a continuous flooring — and I think it 

 will be admitted that the references then made to the defects of 

 that plan of construction will be fully borne out and substantiated 

 by an examination of one, at least, of the experimental constructions 

 of this kind, which has been laid but about eight months, and in 

 which there are already a number of places — some half dozen — 

 where the blocks ai'e loosened fi'om the bed and cement (coal tar 

 and gravel), and settled to some extent, though not yet thrown 

 out of place, and are affected in the manner before described, by 

 heavy vehicle^ moving in the vicinity; and there is little doubt 

 that they are loosened in precisely the manner stated. This speci- 

 men construction of this description of pavement also illustrates 

 fully the difficulty, if not the impracticability, of obtaining a 

 durable grooving between the blocks, by separating them with 

 strips of board or otherwise; for a vacancy having been formed 

 beneath the flooring, as before described, the continual working 

 and springing of the flooring and blocks in many places has 

 loosened the separating strip or picket from the blocks, and forced 

 it up to the top of the blocks, carrying the coal tar and gravel, fill- 

 ing with it up to the surface of the pavement. It must, however, 

 in fairness be admitted that the development of the defects referred 

 to so soon — after so little use — may be owing to the work of laying 

 being defective, from having been done by inexperts or other cause, 

 as this plan of pavement ha^ stood far severer tests for a much 

 longer time. But it illustrates what has been many times before 

 illustrated, that this description of pavement, constructed of small 

 and light blocks, resting upon a continuous flooring, possesses the 

 defects which have been pointed out 



