WATER. 261 



otlier, forming a rude arcli ; — care being taken, what- 

 ever arrangement be chosen, tliat the masses stand 

 with stability. It is of little consequence what sort 

 of rock is selected, — limestone, sandstone, gTanite, 

 conglomerate, — but the rougher, and the more full of 

 cavities and angles, the blocks are, the better will be 

 the effect. 



Water. — The purity of the water is of great import- 

 ance. In London, sea-water may be easily obtained 

 by giving a trifling fee to the master or steward of any 

 of the steamers that ply beyond the mouth of the 

 Thames, charging him to dip it in the clear open sea, 

 beyond the reach of rivers. I have been in the habit 

 of having a twenty gallon cask filled for me, for which 

 I give a couple of shillings. 



The vessel in which it is conveyed requires atten- 

 tion. A cask is the best, if a considerable quantity of 

 water is required ; but it is absolutely indispensable 

 either that it should be new, or at least that nothing 

 injurious should have been previously contained in it, 

 such as spirits, wines, chemicals, acids, &c. ; since no 

 soaking will prevent hurtful qualities from being com- 

 municated to the water. Even the bungs ought to 

 be new ; I knew an instance in which a consignment 

 of animals was lost, fi'om no traceable cause, except 

 that the water-cask, which was quite new, had been 

 stopped with a bung which had been previously used 

 in a jar of some chemical solution ; yet the bung had 

 been, as was supposed, thoroughly soaked and cleansed. 

 If a cask of fir-wood can be procured, it is preferable : 

 the wood of oak, of which wine-casks are usually 

 made, gives out tannin or gallic acid^ to the contained 



