358 MR. A. STRAHAN ON A PHOSPHATIC 



dilute hydrochloric acid, I submitted a specimen to Mr. J. Hort 

 Player, who was kind enough to make a complete analysis of it, the 

 result being to show that the rock consists chiedy of carbonate of 

 lime, but contains from 18 to 35 per cent, of phosphate of lime with 

 a little fluoride of calcium. The analysis is given in full on p. 3(54. 

 The brown colour was attributed by Mr. Player to the presence in 

 the rock of a substance which he believed to be humic acid, and 

 of which he extracted 1 gramme from 1000 grammes of the chalk. 

 His identification of this acid was confirmed by the following analyses, 

 made (by the kind permission of Prof. Thorpe, P.E.S.) by l)r. Tingle, 

 under the direction of Prof. Japp. 



'■''Analyses of Humic Acid from TapJoiv ChcdJc. 



" The substance, dried at 130°, gave the following results on 

 analysis : — 



Analysis I. Analysis II- Analysis III. 



Carbon 65*37 per cent. 63*00 per cent. 



Hydrogen .... 5*70 5*65 



]Xitrogen 3*20 



Oxygen 20*65 22*63 



Ash 5*08 5*52 



96-80 96-80 



" The ash was coloured light red. The analyses, which were made 

 on separate and independent portions, show that the material is not 

 perfectly homogeneous." 



Since making the analysis quoted on p. 364, Mr. Pla3'er has 

 determined that specimens collected from the upper Brown Bed and 

 the lower Brown Bed contain 18-6 per cent, and 35-6 per cent, of 

 phosphate of lime respectivel3^ A rich specimen contains about 65 

 per cent, of the brown grains, and the proportion of phosphate of 

 lime in the brown grains is about 50*6 per cent. 



The rock can be prepared for the microscope (1) by slicing after 

 prolonged heating in Canada balsam, (2) by washing in water, (3) 

 by treatment with strong acetic acid, (4) by treatment with hydro- 

 chloric acid. 



(1) A thin slice of the piped chalk from just below one of the 

 Brown Beds shows white chalk traversed by tubes full of the brown 

 powdery variety. The white chalk contains a few^ scattered 

 foraminifera, all imperfect. The test appears as a sharply defined 

 clear layer, and encloses granular material resembling the matrix, 

 or in some cases a crystalline substance, but in many instances is 

 empty. Manj- of the foraminiferal chambers show a black cross 

 under crossed nicols, this property being especially conspicuous in 

 the empty forms, and being therefore presumably due to a radial 

 structure in the test. Of this white chalk 99-2 per cent, is soluble 

 in cold dilute hydrochloric acid. The tubes before mentioned are 

 sharply defined and are crowded with organisms, most of them filled 

 entirel}^ or partly with an opaque brov\m material. 



