296 Notices respecting New Books. 
‘ 
at all with soap: itis very nearly as soft as the before-mentioned 
pump water boiled. The hardness in it arises from a little sul- 
phate of lime and a little carbonate. 
One of the most striking facts I have observed is, that all spring 
water containing carbonate or supercarbonate of lime, is essen- 
tially démy or alkaline by the colour tests. And this alkalinity is 
not destroyed tili some more powerful acid, suchas the sulphuric 
or muriatic, is added, sufficient to saturate the whole of the lime. 
Indeed these acids may be considered ‘as sufficient for tests of the 
quantity of lime in such waters, and nothing more is required than 
to mark the quantity of acid necessary to neutralize the lime. 
It does not signify whether the spring water is boiled or unboiled, 
nor whether it contains sulphate of lime aloug with the éarho- 
nate ; it is still dimy in proportion to the quantity of carbonate 
of lime it contains. Agreeably to this idea, too, I find that the me- 
tallic oxides, as those of iron or copper, are thrown down by com- 
mon spring water just the same as by free lime. Notwithstand- 
ing this, carbonate of lime in solution with water contains twice 
the acid that chalk or limestone does. I fully expected the su- 
percarbonate of lime in solution to be acid. But it is strongly 
alkaline, and scarcely any quantity of carbonic acid water put to 
it will overcome this alkalinity. Pure carbonic acid water is, how- 
ever, acid to the tests. I could not be convinced of the remark- 
able fact stated in this paragraph, till I actually formed super- 
carbonate of lime, bysupersaturating lime-water in the usual way, 
till the liquid from being milky became clear. It still continued 
limy, and was even doubtfully so when two or three times the 
quantity of acid was added. It should seem, then, to be as impos- 
sible to obtain a neutral carbonate of lime, as it is: to obtain a meu- 
tral carbonate of ammonia in the sense here attached to the 
word neutral. 
—= 
LXVIII. Notices respecting New Books. 
Preparing for Publication. 
Ax Essay on the Strength and Flexibility of Cast lron; with 
Practical Rules and Tables for various Purposes in Engineering 
and Architecture; Remarks on the Forms of greatest Strength ; 
and, an Account of some new Experiments on the Strength of 
Iron. By Thomas Tredgold, Author of * Elementary Principles 
of Carpentry,” and of the Article Jorery in the New Supple- 
ment to the Encyclopedia Britannica. 
Mr. Gill, for many years one of the Chairmen of the Committee 
of Mechanics in the Society for the Encouragement of Arts, 
Manufactures, and Commerce, in the Adelphi, assisted by . 
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