230 



current was passing, which indicated a twist in the plane of polariza- 

 tion of the prolonged beam. The same effect was produced without 

 the iron tube, but not to the same extent. 



Dr. Boye communicated to the Society the results of an 

 Analysis of a Concretion from a Horse's Stomach, performed 

 by Mr. Charles M. Wetherill and himself. 



This concretion, for a fuller description of which, in connexion 

 with its history. Dr. B. referred to his friend, Dr. B. H. Coates, by 

 whom it was handed to him for examination, is remarkable for its 

 size, weighing llf lbs. It is of an oval shape, smooth surface, 

 brownish-grey colour, and breaks in concentric layers of different 

 degrees of thickness, exhibiting a fibrous or radiated structure. The 

 outer layer alone was analyzed. The concretion was found, by Dr. 

 Coates, to contain a nail in its centre. 



By a qualitative examination, it was found to consist of phosphoric 

 acid, magnesia, ammonia, chemically combined water, a small por- 

 tion of organic matter, and silex. It contained no lime. In order to 

 determine quantatively these ingredients, a portion was dissolved in 

 dilute hydrochloric acid; the insoluble residue collected on a coun- 

 terpoised filter, dried and weighed ; after incineration and weighing, 

 it yielded insoluble inorganic matter 0.45 per cent., which, de- 

 ducted from its former weight, gives insoluble organic matter 0.64 

 fer cent. 



To the filtered solution was added a weighed portion of iron wire, 

 dissolved in nitro-muriatic acid, and the whole then precipitated by 

 ammonia. Having previously ascertained the amount of peroxide of 

 iron yielded by an equal portion of the same iron wire, the difference 

 in weight of these two precipitates gave for the phospho7'ic acid, 

 32.40 per cent. 



To the filtered solution from the phosphoric acid, was added caus- 

 tic potash in excess, and the Avhole boiled until the ammoniacal va- 

 pours were effectually expelled, and the solution gave a strong alka- 

 line reaction. The magnesia thus obtained was collected upon a 

 filter, washed with boiling water, incinerated and weighed; it yielded 

 magnesia, 14.45 per cent. 



Another portion of the powdered concretion dried over sulphuric 

 acid in vacuo at ordinary temperatures, yielded hygrometric mois- 

 ture, 1 per cent.; incinerated, it yielded volatile matter (water and 

 ammonia), 51.70 per cent. 



