618 Transactions of the American Institute. 



depth; -which grooves are filled with cement while in a semi-fluid 

 Btate, but which soon becomes hard and solid; thus rendering the 

 block as solid as it was before grooving, while obtaining the advan- 

 tages of a foothold for horses durijig the whole durability of the 

 pa^ ement — that is, the time taken to wear it down to the bottom 

 of the grooves. Joint grooves are also formed where the blocks 

 are in contact, by cutting rebates half the width of the grooves in 

 the face on the sides of the blocks, so that when the blocks are laid 

 in contact, the joint groove is the same width as those in the face; 

 and by which construction, and by using good hard cement, the 

 pavement is not only rendered solid and compact, but is practi- 

 cally impervious to water. The blocks being heavy when filled 

 with cement — weighing over forty pounds each — and having a 

 large bearinor surface, and a large vertical contact fastened together 

 hy hard cement, they will not be easily displaced, even without 

 the use of a sub-sill; but if a sub-sill is preferred, the large area 

 of bearing surface of the blocks makes a " sectional " sub-sill admis- 

 sible, which has all the advantages of a continuous sub-sill, without 

 its disadvantages: the advantages being, ease of removal in getting 

 below it, and making eveiy part of the pavement so solid and sub- 

 stantial, as to be independent of the other portions, and not liable 

 to the disturbance of springing, etc., above referred to. To give 

 additional finnuess where a sub-sill is not used, a dovetailed slot or 

 groove is cut on the sides of the blocks, into which the cement 

 runs from the joint grooves, and hardening, locks the blocks 

 together, and tends to prevent their displacement either vertically or 

 laterally. Or wooden keys may be inserted in the dovetailed 

 grooves, thus securing the blocks or sections — in w'hichever way 

 it may be laid — from any possibility of displacement. 



If it is desired or considered preferable to have but one line of 

 grooves, except at the intersections of the streets, the transverse 

 oi-ooving may be omitted, except at the lateral intersections. The 

 oTOOves may also be made to break joints in one or both directions, 

 either by varying the intei-vals between the grooves, or by the 

 position of the blocks. And to obviate the wearing of the grooves 

 into ruts, as has been the case in some of the plans described, at 

 the intersections of lateral streets, the blocks should be laid at a 

 small angle with the direction of the street, say from twenty degrees 

 to twenty-five degrees. 



The fact of the adoption of wooden pavement to a very large 

 extent in other cities, and almost to the exclusion of all other kinds, 



