1836.] On the solidifying, or induration of Chunam. 98 



that when masonry is excluded from external heat, as it is 

 in works of thick masonry, it solidifies a further portion of 

 the water — therefore it is inexpedient to submit works to the 

 effect of a higher temperature, or rather say to allow it to 

 dry too rapidly. 



But this is not sufficient to give it the indispensable quality 

 of induration, on which strength and permanency depend. 

 The lime as far as has been shewn is only an hydrate com- 

 bined mechanically by the aid of water, — there is another 

 principle wanting — that is carbonic acid. It acquires this 

 from the atmosphere gradually, where other means are not 

 employed to impart it more rapidly — in some places charcoal 

 is added, and it is very often worked up with impure matter; 

 for pure lime is not considered to form the best cement : the 

 purest chunam or lime is obtained from shells. At a distance 

 from the sea coast where these beds or strata of shell are 

 found, what is called stone chunam is used, and is as good 

 as that of shell for masonry, although the native bricklayers 

 prefer the shell. In this part of India the use of jaggery 

 dissolved in water universally prevails, and although it does, 

 there is not a maistry bricklayer, nor even persons who know 

 more, can explain the rationale of its use : some say that it 

 gives an adhesive property from its clamminess — some say 

 that their forefathers used it and so do they their successors ; 

 others laugh at the use of it and pronounce it to be an unne- 

 cessary ingredient and reject it altogether. There is no doubfi 

 that its use may be dispensed with ; the Madras Engineers! 

 it is believed have exploded it altogether, as a measure of 

 economy. 



If we in our days, are more cunning than our ancestors 

 they were more wise ; — no doubt they had their rationale, 

 but like the ancients kept the secret to themselves. Wei 

 give ourselves great credit for our discoveries, but there is 

 good reason for believing that we are only reviving a know- 

 ledge of things lost. But there is great sense in the appli- 

 cation of jaggery or sugar water. Modern chemists have dis- 

 covered the ultimate elements of sugar to be carbon, oxygen 

 and hydrogen. Here we find a grand source and an abundant 

 supply of carbonic acid, or at least the elements of 



