1889.] Barium Sulphate as a Cement in Sandstone. 363 



This research shows distinctly that the decomposition of chlorine- 

 water by light may be divided into two essentially different parts or 

 periods of chemical change, and that the kinds of chemical change 

 occurring during these two periods are largely different. During the 

 first period, a very great and gradual loss of voltaic energy occurs, 

 attended by formation of hydrochloric, hypochloroiis, and chloric 

 acids. Daring the second period, a moderate and very slow increase 

 of voltaic energy takes place, accompanied by decomposition of the 

 hvpochlorous and chloric acids, a farther formation of hydrochloric 

 acid, and the production of peroxide of hydrogen. Under the influence 

 of prolonged sunlight, the whole of the oxygen of the hypochlorous 

 and chloric acids united with water to form peroxide of hydrogen, and 

 the peroxide then combined with the whole of the hydrochloric acid 

 to form a definite " solution compound " represented by the formula 

 2HC1,H 2 2 . 



The chemical composition of the products of the change at the 

 ends of the first and second periods of change was ascertained by 

 means of the voltaic balance and ordinary chemical analysis. During 

 the first period forty consecutive measurements of the voltaic energy 

 at stated intervals of time were made, and the energy diminished from 

 about 1219 millions to 2'9 millions ; and during the second period 

 eight such measurements were made, and the energy increased to 

 9"3 millions. A curve is given showing the rate of loss of energy 

 during the first period. 



It is interesting to observe, that suitably decomposed chlorine- 

 water, or, in its stead, a mixture of 6HC1 + HCIO -f HCIO 3 dissolved in 

 a proper proportion of water, has the property of absorbing energy by 

 exposure to light, very much like that possessed by the green leaves of 

 plants. 



XIV. "Barium Sulphate as a Cement in Sandstone/' By Frank 

 Clowes, D.Sc., Principal and Professor of Chemistry and 

 Metallurgy in University College, Nottingham. Communi- 

 cated by Professor Armstrong, F.R.S. deceived June 6, 

 1889. 



About six miles west of Hottingham there are two prominent 

 conical sandstone hills which are so different in appearance from any 

 surrounding elevations of the surface as to arrest attention. These 

 are known as Stapleford Hill and Bramcote Hill. In the gap between 

 them stands a remarkable sandstone pillar, some 30 feet in height, 

 and 70 feet in circumference, and distinctly crowned by a flattened 

 mushroom-shaped cap. This is locally known as the Hemlock Stone. 

 The sandstone beds forming these hills and columns have been classed 



