852 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



To Prevent the Fading of Photographs. 

 It is well known that the spontaneous decomposition of the 

 hyposulphites used in fixing the photographic picture is one of 

 the chief causes of fading. Several processes have been proposed 

 for remedying the evil, but none seem to have answered the pur- 

 pose. Recently, Messrs. Tichborne and Robinson of Dublin, Ire- 

 land, have devised a process to elminate the hyposulphite without 

 producing any counterbalancing injury. It consists in washing 

 the print in a bath composed of a mixture of bar^'ta and perchlo- 

 ric acid. This mixture has the efiect of removing all traces of 

 hyposulphite without generating any deleterious compound or dis- 

 enirailino: free chlorine e-as which would attack the metallic silver 

 in the pictures. * # 



The Pipestone Quarry. 

 In a sketch of the geology of North-Eastern Dakota, communi- 

 cated to the American Jnunial of Science and Arts, ]>y F. V. 

 Haydcn, will be found a full description of this celebrated Indian 

 quarry. From Fort James, a point on the James river about 65 

 miles north of Yankton, the capital of Dakota territory, the writer 

 proceeded in a direction nearly east for 63 miles to Fort Dakota, 

 at Sioux Falls on the Big Sioux river, where he found red and 

 variegated quartzites similar to those seen on the James river. 

 The falls are five or six in number, extendiua: a distance of half a 

 mile, and have a descent of 110 feet in all, forming the most valua- 

 ble water power he had seen in the west. About ten feet from 

 the top of the rock, as seen in this locality, is a layer of steatitic 

 material, mottled, gray and cream color, very soft, about 12 inches 

 thick, Avhich is sometimes used for the manufacture of pipes and 

 other Indian ornaments. From Sioux Falls to the Pipestone 

 quarry is just 40 miles, measured with an odometer ; direction, a 

 little east of north. The quarry is located on Pipestone creek, 

 and the quartzites here assured Mr. Haydeu that the rocks were 

 of the same age as those on James river and Sioux Falls. The 

 layer of pipestone is about the lowest rock that can be seen. It 

 rests upon a gray quartzite, and there are about five feet of the 

 same quartzite al)out it, which has to be removed with great labor 

 before the pipestone can be secured. The pipestone layer is about 

 11 inches in thickness, only about 2^ inches of which are used for 

 manufacturing pipes and other ornaments. This rock possesses 

 almost every color and texture, from a light cream color to a deep 



