MANUFACTURE AND PROPERTIES OF LIME-SAND BRICKS. 131 



bricks are usually made as large as is convenient for handling and of 

 dimensions to suit the work for which they are intended. The molds 

 are made, several in the same frame, as deep as the thickness of the 

 brick and without any bottom; they are set on smooth ground and 

 filled with mortar. This is worked in a little with the shovel and struck 

 off at the top. In ten or fifteen minutes the mortar will have set, so 

 that the molds can be taken off. The bricks are soon dry enough to 

 handle, when they can be piled up and allowed to dry thoroughly. 

 They are laid in mortar similar to that from which the bricks are made, 

 and the outside of the buildings are roughcast with the same. 



"Several buildings of this kind have been erected in Bridgeton 

 and its vicinity within the last eight or ten years, and in Norristown, 

 Pa., it has been in use for seventeen years past. It has stood well, 

 growing harder and more solid every year. The bricks have come 

 to be a regular article of manufacture in several places. Those of 

 12"X9"X6" were selling in Bridgeton last summer for $20 a thousand, 

 and they could be laid, and mortar found, for $10 a thousand, which 

 is less than half the cost of the same measure of red-brick wall. The 

 material of which these bricks are made being found almost everywhere, 

 and the labor of making and laying them up being very simple, farmers 

 and others who have control of labor can make and lay them at times 

 when the expense of the work would not be felt, and thus a saving much 

 greater than that mentioned could be made. When first laid up they 

 are not quite as strong as other bricks, and greater care is necessary 

 in making a solid foundation, otherwise unequal settling and cracks 

 in the walls will result. Care must be taken to make them so early 

 in the season as to be entirely dry before the winter's frost." 



It will be seen that the general process of lime-sand brick manu- 

 facture is well covered by the above description, and that both the 

 merits and defects of the product are stated rather more frankly than 

 is the practice among its advocates to-day. It is to be kept in mind, 

 however, that the lime-sand brick manufacturers to-day claim that 

 their product derives its hardness, not from a simple recarbonation 

 of the lime, but from a more or less thorough combination of the lime 

 with the silica of the sand or gravel. As this is a matter of interest 

 and importance, it will be discussed in some detail on a later page (p. 133). 

 Whatever the value of their contention may be, it is evident that 

 even this improvement has been anticipated. That a " lime-silicate " 

 brick of modern type was made about 1850 is proven by the following 

 quotation of that date: 



" Recent improvements in the manufacture of concrete building 



