88 Dr John Davy on an Incrustation of Black Oxide, &fc. 



rine is disengaged when it is acted on by muriatic acid, or by 

 dilute sulphuric acid, after the addition of a little common salt. 



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. This example occurs in the 

 valley of Ambleside, and is best seen, where well exposed, on 

 the left bank of the river Rothay, about the middle of the 

 valley. 



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 running 

 water. But when it is seen that the colouring matter is not 

 to be detected on the rocks in situ, the fixed rocks in the 

 course of the stream, the idea ceases to be tenable, and the 

 inference seems to be unavoidable, that the sand, pebbles, 

 and stones thus coloured have been incrusted with the oxide 

 (in whatever manner that may be effected) before they had 

 been carried down to the spots where they are found loose ; or, 

 when in the form of conglomerate, that the cementing oxide 

 has been brought there by water exuding from some rock or 

 stratum containing manganese in a minor degree of oxida- 

 tion, and acquiring the higher degree by the absorption of 

 oxygen, and at the same time the cementing quality. 



Hitherto, no mine of manganese that I am aware has been 

 opened in this district, nor any accumulation of it found to 

 tempt mining enterprise. The occurrence of the black oxide 

 in the manner described is surely an indication of the exist- 

 ence of this useful mineral in large quantities, and should 

 excite special inquiry, — an inquiry likely to be rewarded with 

 success, if made with care and by competent persons. 



1. Parasites and their Belations to other Animals. 



2. Parasitic Life. 



At a meeting of the Boston Society of Natural History in 

 February, Dr Burnett presented a communication on the 

 relations of an order of parasites (^pediculus)^ to the different 



