CHEMICAL SCIENCE. 175 



slightly heated and covered over with a thin coat of Canada balsam, 

 dissolved in turpentine, after which they are kept warm until the tur- 

 pentine is driven off. Various colored substances may be used along 

 with the materials specified to color the artificial marble, such as indigo 

 for blue, and other substances for other colors. The marble may also 

 be streaked and beautifully variegated. Scientific American. 



ON THE DISTRIBUTION OF MANGANESE. 



AT the American Association, Albany, the following paper, on the 

 " Distribution of Manganese," was presented by Mr. David A. Wells, 

 of Cambridge : 



"The occurrence of pebbles and water-worn stones in many of the 

 streams and water-courses of New England, which have their origin 

 among, and run over, igneous and metamorphic rocks, is by no means 

 uncommon, and has doubtless attracted the attention of every observer. 

 When the bed of a stream in which they occur, is examined, the colored 

 pebbles and stones will be found at intervals, generally after or below a 

 fall or rapid, and not immediately above. This coloring matter, which 

 is wholly superficial, and of different degrees of lustre, is due to an in- 

 crustation of the black oxide of manganese, and occurs independently 

 on almost every variety of stone. 



" In the Edinburgh New Philosophical Journal, for July, 1851, Dr. 

 John Davy calls attention to somewhat similar incrustations, in Eng- 

 land, of which he says as follows : 'Though always superficial, in 

 one spot the incrustation is so thick as to be available for use ; and in 

 this instance the black oxide of manganese acts as a cement, forming a 

 bed of conglomerate several feet thick. Whence this incrustation is 

 derived, or how produced, is not obvious. Restricting the view to the 

 spots where it occurs, it might be supposed to be a deposit from run- 

 ning water. But when it is seen that the coloring matter is not to be de- 

 tected on rocks in situ the fixed rocks in the course of the stream 

 the idea ceases to be tenable, and the inference seems to be unavoida- 

 ble, that the sand, pebbles and stones so colored have been incrusted 

 with the oxide before they had been carried down to the spot where 

 they are found loose ; or, when in the form of conglomerate, that the 

 cementing oxide has been brought by water exuding from some rock or 

 stratum containing manganese in a minor degree of oxidation, and ac- 

 quiring the higher degree by the absorption of oxygen, and at the same 

 time the cementing quality.' Dr. Davy also infers that manganese 

 exists in the vicinity of these incrustations in large quantities, and 

 advises special inquiry in search of it. 



"Before the publication of the article referred to by Dr. Davy, the 

 subject of these incrustations had attracted the attention of Dr. A. A. 

 Hayes, of Boston, and myself, and we believe the following to be a full 

 and satisfactory account of the origin of this phenomenon. 



" The manganese exists in almost all the igneous and metamorphic 

 rocks of New England, and I may say in other parts of the world, gen*- 

 erally as a double carbonate of lime and manganese. When the waters 

 of the springs, brook and rivers, flowing over these rocks, become 



