CLAY WORKING INDUSTRIES. 203 



This same difference extends to the use of the brick in the streets ; 

 the large material may lose as much in five years as the small, but 

 there are twenty to thirty per cent less brick used in paving any given 

 area and twenty to thirty per cent less joints and points at which failure 

 is probable. Also while the strength to resist a breaking strain is not as 

 high per inch of surface or bulk, it is as high per brick as the smaller 

 ones. 



A prejudice has existed in some quarters against the large blocks in 

 the alleged difficulty of vitrifying them. By the test it will be seen 

 that there is practictically no difference in the vitrification of large and 

 small blocks; as a matter of fact, the difficulty of burning large blocks 

 comes in avoiding the bloating tendency when expelling the combined 

 water. A very few hours of time and a very few pounds of coal are all 

 that is required to vitrify the extra half inch in thickness which makes 

 the brick classed as a "block." 



The manufacture and sale of vitrified material for paving purposes 

 is a new business, and one which is still in the early stages of evolution. 



Five years ago, there was not a brick company in the state of Ohio 

 which had any comprehension of the needs and necessities of the con- 

 tractors, whom they so cheerfully agreed to furnish with vitrified brick. 

 The manufacturers have been learning in the hard school of experience 

 these five years. 



One of the great temptations of the manufacturer has been to grade 

 his product leniently. Especially has this been true of all manufacturers 

 who have been making paving blocks, or bricks of special shape and 

 size, designed for street use only. To the maker of this class of wares, the 

 merciless system of rejecting anything in any way deficient has been almost 

 an impossibility. It has meant in many cases a balance on the wrong 

 side of the ledger at the end of the year. And above all the cheerful 

 ignorance of those who have been inspecting and laying this material has 

 made the moral strain on the manufacture still more severe. 



The soft brick, or those which do not receive sufficient heat to vitrify 

 them, and the culls or those, which, while hard enough, are cracked, 

 twisted, or chipped, constitute a regular percentage of every kiln's con- 

 tents. The best burning in the state produces some. The average burn- 

 ing produces twenty-five per cent, to thirty per cent, of material which 

 has no business in the street. 



Many companies in starting out have not made fifty per cent, of 

 merchantable material in the first six months. The culls must be dis- 

 posed of for some secondary purpose. The soft brick can now be burn t 

 over again and made merchantable, at an increased cost of ten or twelve 

 dollars per thousand. 



The advantage of paving blocks over brick are being recognized on 

 all sides. In Ohio, the Hallwood block was put into the market in 1888 ; 

 now there are not less than ten different brands of blocks all of which 



