CHEMICAL SCIENCE. 193 



was launched in December, 1863. Previous to that, her hull was 

 covered with two coats of paint, the base of which consisted of 

 metallic zinc in powder, and then with minium paint containing 

 ten per cent, of M. Jouvin's poisonous composition. After re- 

 maining fifteen montlis in the water, she was placed in the dry 

 dock, when hex' hull was found to be covered with a gray, mud- 

 like matter, to the sui'face of which a few mussels had attached 

 themselves by their byssus, thus being isolated from immediate 

 contact with the poisonous composition. A slight touch was suf- 

 ficient to detach them. They were principally collected on the 

 spots at which the struts had been fixed, which were only painted a 

 few moments before the vessel was launched. There were no 

 marine plants, and no barnacles. These results seem to be highly 

 satisfactory, since neither plants nor moUusks can attach them- 

 selves, and the bottom may be cleaned by brushes, or even by 

 rubbing with a piece of wood, without the necessity for scraping. 



SULPHURETTED HYDROGEN, 



This gas, which, for experimental purjjoses, is usually obtained 

 by means of sulphuret of iron, may be procured more conveniently, 

 and in a state of great j)urity, by the use of sulphuret of calcium. 

 The latter is formed very easily by mixing uncalcined powdered 

 gypsum with one-fourth of its weight of calcined gypsum, and pow- 

 dered pit coal equal to one-third of the whole of the gyjisum used, 

 and working up the mixture to a stiff dough with water ; next form- 

 ing it into pieces four inches long, two wide, and one and a-half 

 thick, sprinkling them with powdered coal, and drj'iug them ; then 

 placing them with coke in a wind furnace, and keeping them at a 

 very high temperature for two hours. When cold, they will be 

 found, externally, to consist of oxysulphuret of calcium ; but, in- 

 ternally, of pure peach-colored suljihuret of calcium, which may 

 be broken in pieces about the size of nuts, and preserved in well- 

 stoppered glass bottles. If water is added to these, and then sul- 

 phuric acid in small quantities at a time, sulphuretted hydrogen 

 is given off with great uniformity. — Scientific Review. 



ACTION OF SEA-WATER UPON METALS. 



In a paper by Messrs. Calvert and Johnson, in the London 

 "Mechanics' Magazine" for March, 1865, are given the results 

 of experiments in which twent}' square centimetres of various 

 metals, carefully cleaned, were immersed in equal volumes of 

 sea-water for the space of one month ; the conclusions are as 

 follows : 1. That the metal now most in vogue for shipbuilding, 

 namely, iron, is that which is most readily attacked. 2. That 

 this is most materially preserved from the action of sea-water 

 when coated with zinc, and, therefore, in our opinion, it would 

 amply repay shi2)builders to use galvanized iron as a substitute 

 for that metal itself. The above facts fully confirm those pub- 

 lished in a previous paper, in which it was shown that when iron 

 was in contact with oak they mutually acted upon each other, 

 17 



