254 THE TANK. 



glass with white lead, leaving about a quarter inch in 

 depth of the groove unfilled. When the putty is set, 

 I fill it up with shell-lac dissolved in naphtha and 

 made into a paste with whiting. This sets very 

 quickly ; and, hard as stone, is quite insoluble, and 

 prevents the water from coming in contact with the 

 lead, which I think must constantly be giving off 

 small quantities of oxide." 



In reply to some inquiries of mine, the same 

 gentleman writes me further as follows : — 



" I have delayed replying to you respecting the 

 price of pottery for Aquariums till I had an oppor- 

 tunity of seeing the party who made mine. The 

 price of one such as you name would be 6s. or 8s. , 

 but, as it would weigh four hundredweight, the 

 carriage to London would be quite as much. He was 

 rather doubtful whether with his coarse clay he could 

 make one the length you name to hold together ; as 

 two or three of mine, which were shorter, separated in 

 the middle when being burnt, from the great weight 

 of the ends preventing the centre contracting regu- 

 larly. He thinks your best plan would be to get one of 

 the terra-cotta workers to make one, wliich he thinks 

 he would do more cheaply than it could be sent from 

 here ; and their clay being finer, a much neater article 

 could be made. It would be well to be on the spot, 

 and see the rough clay put on the ends, as workmen 

 in general have not much idea of what is required. 



" To prevent the water filtering through the pots, 

 mine were well glazed inside with flint-glaze, free 

 from lead. Probably it would be better to glaze the 

 outside, and leave the inside porous." 



