1849.1 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



349 



Expansion of Mercury. 



THE WATER FROM THE CHALK FORMATION. 



Analysis of the Water from the Chalk Formation. By Messrs. 

 Abel and Rowney, Assistants at the Royal College of Chemistry. 



The deep well water of the London basin has been analysed by 

 Professor Graham. The strilving feature of this analysis is, the 

 discovery of the presence of sulphuric acid, and the absence of 

 salts of potash. The water which he analysed, was taken from the 

 deep well in the brewery of Messrs. Combe and Uelafield, Long- 

 acre. This well not descending so deep into the chalk as the 

 Artesian wells in Trafalgar-square, induced Messrs. Abel and 

 Rowney to subject the water of the latter to an analysis, in order 

 to compare the results with those obtained by Professor Graham. 

 The water on which they operated was taken in the beginning of 

 October, 1847, from the shaft at the back of the National Gallery. 

 At a depth of about 109 feet, the water enters the shaft througha 

 borehole, which passes the London clay and penetrates into the 

 chalk. Thus the water rises from a depth of nearly 400 feet. 



The temperature of the water is 58° Fahrenheit., its specific 

 gravity is 1000^95, the specific gravity of distilled water being 

 1000. The water is very soft and very delicate; test-papers show 

 that it has an alkaline reaction. 



The subjoined analysis shows that the constituents of the water 

 of the Artesian wells in Trafalgar-square, are essentially the 

 same as those of the water from the well in Messrs. Combe and 

 Delafield's brewery. There is only one point in which the two 

 waters materially diifer in composition. The waterwhich Profes- 

 sor Graham analysed, and which, as already mentioned, comes from 

 a higher stratum, was found to contain no potash salts, whilst 

 these were invariably present in the water of Trafalgar-square. 

 In order to preclude the possibility of error, the water employed 

 for testing was collected at diiferent periods. 



M. Payen found that the water of the Artesian ^7ell at Greuelle 



contained a considerable amount of sulphate of potash and chloride 

 of potassium, so that it would appear that potash salts are charac- 

 teristic of the waters from the deeper strata. 



The water analysed by Messrs. Abel aud Rowney did not contain 

 a trace of iron. 



Annexed is a tabular view for the comparison of the water 

 analysed by Professor Graham, and the Trafalgar-square water, to 

 which is anne.xed the results obtained by M. Payen from the 

 analysis of the water of Grenelle, each showing the number of 

 grains in an imperial gallon. 



The presence of phosphoric acid, first pointed out by Professor 

 Graham in deep well water, could be easily ascertained in the Tra- 

 falgar-square water, by the method indicated by that chemist; in 

 fact, on evaporating the water to dryness, and gently igniting the 

 residue, the phosphoric acid, existing partly in combination with 

 lime and partly with soda, is obtained altogether in the form of a 

 soda salt, the solution of which deposits the yellow tribasic silver 

 salt on the addition of nitrate of silver. 



The large amount of organic matter contained in deep well 

 water is very remarkable, while the quantity observed in the water 

 of a higher stratum seems to have been very trifling. It evidently 

 arises from the remains of organised beings which have invariably 

 been found in the chalk. 



With reference to the quantities in which the different consti- 

 tuents are present, it will be observed, on comparison, that the 

 total amount of fixed constituents is somewhat different (56'80 and 

 69^40), whilst very considerable deviations are perceptible in the 

 quantities of the various constituents. 



The most striking difference is observed in the quantities of sul- 

 phate of soda contained in the two waters. 



ROYAL SCOTTISH SOCIETY OF ARTS. 



The following communicationa were made : — 



1. ^'Improvements in Fixed and Revolving Lights, being a New Dia- 

 Caioptric Instrument for increasing the intensity of the light." By Thomas 

 Stevenson, Esq., F.1«.S.E., C.E. 



The author stated that this instrument is composed of three parts— & 

 paraboloidal mirror, having the conoidal portion behind the parameter cut 

 off, and its place supplied by a hemispherical reflector, whose centre thus 

 coincides with the focus of the paraboloid, while in front of the flame is 

 placed an annular lens subtending at the focus of the paraboloid, the same 

 angle as that which is subtended at that point by the greatest double ordi- 

 nate of the reflector, and having its piincipal focus coincident with that of 

 the paraboloid. This instrument should theoretically produce the most in- 

 tense light yet derived from any given flame, as it incloses and parallelizes 

 each ray of the whole sphere of light, so that none are lost by divergence 

 between the lips of the reflector, where, in the preseHt arrangement, not 

 very much short of one-half of the light is lost. 



In this instrument the hemispherical reflector throws the light which it 

 receives (viz., the posterior half of the sphere of light) through the focus of 

 the paraboloid, and while the outer ring of this light is received by the para- 

 boloid, and parallelized by it, the central cone is received by the annular 

 lens, and is also parallelized. The outer ring of the anterior half of the 

 sphere of light is received directly by the paraboloid, and is parallelized by 

 it ; while the central cone of rays, which, in the present arrangement, is 

 lost by natural divergence, is received by the annular lens, and is parallelized 

 by it. Thus the whole sphere of light is economised. This combination 

 may also be applied mutatis mutandis to the illumination of half of the ho- 

 rizon of a fixed light, hy means of a single light : the only difference being 

 the substitution of two truncated parabolic conoids (or the paraboloid, auii a 



