228 Scientific Intelligence. [March, 



III. Remarkable Stone found near Derby. By J. D. Strutt, Esq. 



(To Dr. Thomson.) 

 SIR, Derby, Nov. 13, 1817. 



I have sent for insertion in your Annals an account of a large 

 block of stone, which was discovered, a few months ago, when 

 lowering Chaddesden Hill, about a mile on the eastern side of 

 Derby, and which may, perhaps, be interesting to some of your 

 readers. This block measures about two feet long, 20 inches 

 wide, 14 inches in height, and weighs about four hundred weight 

 and a half. It has the appearance of an irregularly rounded boulder 

 stone, and is composed of greenstone, interspersed with particles 

 of hornblende. It is exceedingly hard, and is not at all similar 

 to any species of stone which is found in this neighbourhood. 

 A number of the bones of some animal were found underneath 

 it. It is supposed that this stone was placed there by the Saxons 

 to mark the boundary between this borough and Chaddesden, 

 and that it was brought by them from some distance ; because 

 it is known they always preferred, for this purpose, some kind 

 of stone of which there was none similar in the neighbourhood, 

 in order that no mistake or disputes might arise concerning the 

 boundary. The bones which were found underneath it are sup- 

 posed to be those of the animal which they sacrificed when the 

 boundary mark was placed there, as was the custom of the 

 Saxons on these occasions. I am, Sir, 



Your obedient servant, 



J. D. Strutt. 



IV. Oxides of Manganese. 



We learn, by a letter from Professor Berzelius to M. Gay- 

 Lussac, that M. Arvidson, a young Swedish chemist, has 

 been engaged in a series of experiments upon manganese, 

 from which he concludes that it has three degrees of oxida- 

 tion. The colour of the protoxide is green, that of the two 

 others is black. The second oxide is formed, either by 

 means of the nitric acid, in heating the nitrate of manga- 

 nese, until it assumes a reddish brown colour, or by burning 

 the protoxide in the atmosphere. If the second oxide be 

 urged by a continued red heat, a little oxygen gas is disengaged, 

 and a red powder is left, which, by means of acids, may be 

 decomposed into the green oxide and the black oxide. This 

 black oxide, however, is not the peroxide, but the deutoxide. 

 The red powder is composed of 100 parts of manganese and 

 37*47 parts of oxygen ; whilst, in the deutoxide, 100 parts of 

 the metal are combined with 42-16 parts of oxygen. The red 

 oxide of manganese seems, then, to be analogous to the oxide 

 of native magnetic iron. M. Arvidson has. also examined the 

 native peroxide. He has found that this oxide, by a powerful 



