Proceedings of the Polttechxic Association. 715 



powdered zinc and the application of heat ; when it is completed, the 

 mass is diluted with water, and the abundant precipitate is the 

 required dve, which, after being washed with water, is ready for use. 

 Thus orange-madder, purpurine, pseudo-pm-purine and Xanthro-pur- 

 purine are transformed into alazarine. This process for making 

 available all the coloring matter in madder seems to be important in 

 a pecuniary, as well as scientific, point of view. 



A Remakkable Mineral Spring. 

 The water of a medicinal spring on the Island of Jamaica has been 

 analyzed by Dr. Attfield, of London, and found to contain a larger 

 quantity of chloride of calcium than any other natural water now 

 known. It is clear, inodorous, and strongly alkaline to the taste. 

 One gallon of it holds in solution about three and a half ounces of 

 chloride of calcium, two ounces of common salt, and two and a half 

 grains of chloride of ammonium. It has been used for medicinal pur- 

 poses by the negroes of the island for th© last forty years, and has 

 been found most beneficial in scrofulous diseases, glandular swellings, 

 etc. The spring is sixty-eight feet above the sea, and nearly a mile 

 from it, rising through a diluvial gravel that forms the bed of a small 

 stream near Saint Ann's, on the northern coast. 



SiKIUS. 



Mr. C. Abbe, of the Pulkova Observatory, has, by means of the 

 meridianal observations, of Sirius, made with the transit circle at the 

 Cape of Good Hope, adduced a parallax lying between thirty-seven 

 and seventeen one-huudredths of a second. The brightness of Sirius, 

 it being four times greater than that of any other fixed star visible in 

 the northern hemisphere, would lead us to expect a greater diiference 

 in the directions of the telescope when upon that star at opposite 

 points in the earth's orbit, 190,000,000 miles apart ; and, at any rate, 

 tliat the parallax might be determined with a less probable error than 

 has been assigned by Peters to several stars of inferior magnitude. 

 According to Abbe, the distance of the dog star is not less than 

 663,000 times the diameter of the earth's orbit, or greater than 1,224,- 

 000 times that diameter. Taking the least sum as the true distancei 

 some faint conception may be formed of its vastuess by the statement 

 that an object moving as fast as the earth rotates at the equator, or 

 1,000 miles an hour, would require more than 12,200,000 years to 

 pass from our planet to Sii'ius. 



