332 Notices of Memoirs — Prof. A. H. Church — 



mens I found a high per-centage of feme oxide, with very little 

 silica and alumina. Mr. E. C. Clapham had shown, 1 however, that 

 some samples, at all events, of red chalk contained as much as 9 - 28 

 per cent, of silica, with 9-6 per cent, of ferric oxide and 1*42 per cent, 

 of alumina, and that these three ingredients were also present in 

 white chalk, though in much smaller proportions. 



In view of the recent discoveries as to the materials constituting 

 the floor of the deep sea, and acting upon a suggestion made by 

 Professor J. Morris as to the probability of some near connexion 

 between red chalk and the "red clay" of certain deep tracts of the 

 ocean bottom, I have again studied the chemical nature of the 

 former material; but this time I employed a different method of 

 analysis, and I operated upon the paler and more ordinary variety 

 of red chalk. The samples used were numerous, but the results of 

 the treatment, to which they were submitted were nearly uniform. 



The following is a brief outline of the plan which was pursued in 

 order to see if it were possible to separate from red chalk a red 

 clay, slime, or ooze, similar to that which is reported by the officers 

 of the Challenger Expedition to cover the Atlantic bed at average 

 depths of some 2700 fathoms. Treatment with very dilute hydro- 

 chloric acid in the cold seemed the best way of removing the 

 calcium carbonate present. This acid was allowed to act upon 

 small crushed pieces of selected red chalk until fresh acid failed to 

 remove any further traces of calcium. By appropriate washing in 

 an apparatus similar to that figured in my " Laboratory Guide," 2 

 the finer portion of the undissolved residue from the chalk was 

 readily separated from the siliceous fragments which accompanied it. 

 This finer portion remains suspended for some time when stirred up 

 in pure water, and was found to be almost, if not quite, homogeneous ; 

 it contained no lime. It amounted, on the average, when air-dried, 

 to 9-3 per cent, of the weight of the chalk taken, but some dark 

 samples furnished higher per-centages. Its physical characters corre- 

 spond, so far as I can learn, to those of the red residue obtained by 

 Mr. Buchanan from the G-lobigerina ooze, and to those of the smooth 

 red clay before referred to as brought up from the deeper parts 

 of the sea-bottom. 



The following analysis abundantly proves how closely the chemical 

 composition of the red argillaceous residue from red chalk resembles 

 the red clay in question ; — 



Analysis of Bed Clay from Bed Chalk. 



In 100 Parts. 



, A 



Air-Dried. Dried at 100° C. Ignited. 



Water 1473 7-54 — 



Silica 52-87 57"33 62-01 



Ferric oxide (Fe 2 3 ) . . 12-81 13-89 15-02 



Alumina 15-65 16-97 18-36 



Magnesia (MgO) . . . 2-65 2-87 3-11 



Potash (K 2 0) .... 1-33 1-45 1-56 



100-04 100-05 100-06 



1 1862. Chemical News, vol. vi. p. 313. 



2 "Laboratory Guide," 3rd edition, 1874, p. 163. 



