54 REPORT — 1855. 



so easily and rapidly performed, that he thought it advisable to test its accuracy, and 

 the following results leave no doubt as to its exactitude and value. The zinc is de- 

 termined by difference. 



Taken. Obtained. 



I. Copper 1-16 117 



Zinc 17-97 17-96 



II. Copper 9-91 9-935 



Zinc 3-55 3-525 



Description of Dr. Clark's Patent Process for softening Water, now in 

 use at the Wo7-ks of the Plumstead, Woolwich, and Charlton Consumers' 

 Pure Water Company, togetlier with some Account of their Works. By 

 D. Campbell, F.C.S. 



According to the author, the process of Dr. Clark for softening water may be applied 

 with advantage to water from the chalk strata, water from the New Red Sandstone, 

 and waters which contain carbonate of lime in solution from any strata. It is briefly 

 described as follows ; namely, by adding a quantity of milk of lime to the water, it takes 

 carbonic acid holding carbonate of lime in solution ; and forms a precipitate of carbonate 

 of lime, throwing down at the same time thequantity of carbonate oflime held in solution 

 by the carbonic acid, and thus rendering the water soft. The works and operations for 

 carrying out the process were fully described by diagrams. One peculiar feature in the 

 •water after it had been softened, and which was not anticipated by Dr. Clark when he 

 first took out his patent, is, that it does not show the slightest sign of vegetation, though 

 exposed to the sun and light for upwards of a month, whilst the water before softening 

 cannot be kept above a few days without producing Confervre ; and if this be not 

 immediately removed, decay commences quickly, and small insects are soon observed, 

 which feed upon the decaying vegetable matter ; and the water soon assumes a bad 

 taste. This is continually the case when the water is kept in large reservoirs, and its 

 removal occasions considerable trouble and expense. The author had endeavoured to 

 explain the reason of this marked difference between the imsoftened and the softened 

 water; and he was nearly satisfied that the vegetating principle in the water was more 

 especially due to the carbonic acid holding the carbonate of lime in solution than to 

 the volatile matter, or, as it is sometimes called, oi-ganic matter. The process is 

 applicable to many towns already supplied with water from the chalk and from the 

 New Red Sandstone, and if properly applied will be found to pay the expense of its 

 working, and confer a great boon upon the populations, the enlightenment of whose 

 corporations may induce them to adopt it. 



On the Preservation of the Potato Crops. 

 By Chevalier De Claussen. 



At the meeting of the British Association in Hull, two years ago, the author proposed 

 sulphate of lime as a means of preserving the potato. He has since, by successive 

 experiments, convinced himself that it is entirely efficient. He wets them with water 

 acidulated with sulphuric acid (1 part acid, 500 parts water), and before they are dry 

 throws over them powdered sulphate of lime, or plaster of Paris, by which process 

 they are covered with a thin film of sulphate of lime. If the potatoes are already 

 attacked partially with the disease, they must be left from six to twelve hours in the 

 acidulated water before the sulphate of lime is used ; but in case they are free of 

 disease, a few minutes are sufficient. It is very possible that sulphate of lime, with 

 an excess of sulphuric acid added to the soil in which potatoes grow, may be useful ; 

 but he has not made any experiment to this purpose. He has ground to suppose that 

 chemical combinations in contact with animal or vegetable products have a tendency 

 to preserve them, in the same way as the combination of oxygen and zinc preserves 

 iron, and that this is one of the causes why the combination of water with the sul- 

 phate oflime preserves potatoes and other vegetables; and that in the same time the 

 small quantity of free sulphuric acid destroys the fungus which causes the disease. 



