TANKS AND CISTERNS. 



513 



influence of my salts be represented by 

 100° : in this condition they are capable 

 of reducing water from a temperature 

 132° to the point of congelation ; but the 

 same charge of salt would not reduce boil- 

 ing water to a like condition, unless the 

 charge be again repeated. Thus the same 

 quantity of salt (represented by 100°) 

 would reduce boiling water to a tempera- 

 ture of 112°; and a second charge being 

 placed in the room of that now exhausted, 

 would infallibly convert the previous boil- 

 ing water into ice ; — therefore it is a desi- 

 deratum in all cooling processes to have 

 the liquids to be congealed as cool as 

 possible, in order to facilitate the opera- 

 tion of congelation; still, by repeated 

 quantities of freezing mixture, any sub- 

 stance may be reduced from any point 

 down to 32°, the freezing-point of water, 

 the point of its conversion into ice, and 

 even much beyond that." 



Freezing Mixtures without Ice. 



50° 



Mixtures. 

 ( Muriate of ammonia, . 

 1. < Nitrate of potash, 

 (Water, 

 Lowers thermometer from + 



f Muriate of ammonia, . 

 2 1 Nitrate of potash, 

 j Sulphate of soda, 

 (Water, 



From + 



( Nitrate of ammonia, . 

 3. < Carbonate of soda, 

 ( Water, 



From + 



4 { Water, 



| Nitrate of ammonia, . 



From + 



g { Sulphate of soda, 

 ( Diluted nitric acid, . 



From + 



( Sulphate of soda, 

 q ) Muriate of ammonia, . 

 j Nitrate of potash, 

 ( Diluted nitric acid, 



From + 50° to 



I Sulphate of soda, 

 7. < Nitrate of ammonia, 

 ( Diluted nitric acid, 



From + 50° to 



g [ Phosphate of soda, 

 ( Diluted nitric acid, 



From + 50° to 



{Phosphate of soda, 

 Nitrate of ammonia, 

 Diluted nitric acid, 



From + 50° to 



VOL. I. 



Parts. 

 5 

 5 

 16 



50° to + 10°. 



5 

 5 

 8 

 16 



to + 4°. 



50° 



50 c 



50° 



1 

 1 



to — 7°. 



1 

 1 



to + 4°. 



3 

 2 



to + 3°. 



4 

 2 

 4 



10°. 



6 

 5 

 4 



14°. 



9 

 4 



12°. 



9 

 6 

 4 



21°. 



10. 



11. 



12. 



13. 



| Sulphate of soda, ... 8 

 \ Muriatic acid, .... 5 

 Lowers thermometer from + 50° to 0°. 



j Sulphate of soda, 

 ( Diluted sulphuric acid, 



From + 50° to 



( Pulverised muriate of ammonia, 

 < Nitrate of potash, 



( Water, 



From + 



( Sulphate of soda, 

 1 Muriate of ammonia, ... 4 

 j Nitrate of potash, ... 2 

 ( Diluted nitric acid, ... 4 

 From + 50° to — 10° 



5 

 4 



+ 3 C 



5 

 5 



. 16 



50° to — 10° 



6 



§ 4. — TANKS AND CISTERNS. 



The great utility of tanks and cisterns 

 has hitherto been much overlooked in 

 gardens : indeed, a sufficient supply of 

 water has been seldom thought of ; and 

 this is the more extraordinary, as so much 

 depends on its presence; for, as old 

 Switzer remarked, " water is the soul of a 

 garden ; " — without it all the other ele- 

 ments of nature are useless and unavail- 

 able. — Vide article Water. 



Tanks are of various constructions, and 

 for various purposes : viz. filtering-tanks, 

 liquid-manure tanks, rain-water tanks, 

 and general reservoir tanks, &c. Smaller 

 water vessels are called cisterns, and are 

 usually set in or attached to hothouses, 

 &c. 



Filtering water is a simple process, 

 employed to purify or sift out earthy or 

 other heterogeneous matter out of river, 

 rain, or other water, that may not be con- 

 sidered sufficiently pure to be used for 

 culinary or other domestic purposes. 



Waistell, in "Designs for Farm-Build- 

 ings," thus describes a filtering tank used 

 by him, of which the 

 annexed diagram, 

 fig. 729, will show 

 the principle: "The 

 bottom should be 

 in the form of a 

 flat dome reversed, 

 and the top also 

 domical, with an 

 opening left in the 

 centre of sufficient 

 size to admit a man to clean it out occa- 

 sionally : the top of this opening should 

 be a little above the surface of the ground, 

 and should be covered with an oak flap, 



3 T 



1 1 





1 





