CHAPTER X. 

 MANUFACTURE AND PROPERTIES OF LIME-SAND BRICKS. 



THE term lime-sand brick will be used in this volume to cover 

 all bricks made by mixing sand or gravel with a relatively small per- 

 centage of slaked lime, pressing the mixture into form in a brick mold, 

 and drying and hardening the product, either by sun-heat or artificial 

 methods. The general process is not in any way patentable, being 

 of very ancient date. Various details of the process may, however, 

 be covered by valid patents, such, for example, as on the type of 

 molding-press used, on the exact methods and appliances for drying 

 and hardening, and on various more or less "secret" compounds which 

 may be added to facilitate hardening or to increase the final strength 

 of the product. 



Early history of the industry. Though in the past few years the 

 "invention" of lime-sand brick has been heralded as a new matter, 

 the general process has been employed for many years both in America 

 and in Europe. 



The following interesting contemporary account * of the manu- 

 facture and use of lime bricks in New Jersey in 1855 incidentally estab- 

 lishes the fact that the industry had been known near Philadelphia 

 since 1838. 



" Gravel bricks. A new building material has been introduced in 

 Cumberland and some of the adjoining counties which promises to 

 be both cheap and durable. The common clean gravel and coarse 

 sand of the country is mixed with one' twelfth its measure of stone lime 

 and made into bricks. These bricks are sun-dried and then laid up 

 into walls. They are cheap, durable, and but little affected by the 

 changes of the seasons. 



"In making, the gravel is laid on a common mortar bed, and the 

 lime, which is slaked and made into a thin putty in a lime-trough, is 

 then run on the gravel and the whole worked up into mortar. The 



* Cook, G. W., in Second Ann. Rept. of the Geol. Surv. of the State of N. J. 

 for the year 1855, pp. 107-108. 1856. 



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