Analyses of the Hydrates of Baryta and Strontia. 301 



tral fins are placed opposite each other, as also are the anal 

 and what appears to be the posterior dorsal. Here a discre- 

 pancy exists. In recent Salmonidae, the latter fin is merely 

 a fleshy appendage, and not supported by rays. In the fossil 

 specimen the fin, though imperfect, exhibits traces of true rays. 

 Though this will prevent its being considered one of the Sal- 

 monidae, I know none other of the abdominal Malacopterygii 

 that have the same arrangement of the fins: this fact, com- 

 bined with the resemblance between the scales, which differ 

 only in the existence of radiating striae at one extremity of the 

 fossil, which do not exist on the recent ones, seems to indicate 

 a close affinity. The discovery of more complete specimens 

 may throw new light upon their nature. 



XXXV. Analyses of the Hydrates of Baryta and Strontia. 

 By H. M. Noad, Esq., Lecturer on Chemistry. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



/~\N looking over some of the back Numbers of your Ma- 

 VJ gazine, which have only lately come into my hands, I met 

 with a paper by Mr. J. D. Smith on the hydrates of barytes 

 and strontia, in which he seems to think that the previous de- 

 termination of [the quantity of water combined with these 

 metallic oxides, by Mr. Phillips, is not correct. On referring 

 to my journal, I found the results of an analysis of these hy- 

 drates by myself performed about two years ago, and having 

 some crystals of each at the bottom of two bottles in which 

 they had remained since that time, I determined to analyse 

 them again, with the greatest care, as my results did not 

 exactly correspond with those of Mr. Smith. As my recent 

 experiments coincide exactly with my former ones, perhaps 

 you will allow them to be inserted in your Journal, for the 

 inspection of Mr. Smith and others. I must observe that the 

 greatest care was taken to get the crystals perfectly dry by 

 pressure between folds of blotting-paper. 



Bar. Sulph. of Bar. Bar. Water. 



Exp. 1. 37-5 gave 26*75 = 17*56 + 19-94- 



Exp. 2. SO* gave 21-5 = 14*11 + 15-89 



Exp. 3. 26* gave 18*62 = 12*22 + 13*78 



43*89 49*61 



or 76*7 one equivalent of baryta combined with 8669 nearly 

 9 J equivalents of water. 



