Intelligence and Miscellaneous Articles. 311 



and have never found it absent. Indeed the former experiments 

 have demonstrated, that on those rocks where we find lichens grow- 

 ing, we may infer the presence of phosphoric acid and of various 

 salts ; and the same inference applies to all localities where marshy 

 vegetation exists. 



Greenstone Soil. — The following analyses were made by Mr. James 

 Paterson, Barnego, near Denny. The greenstone upon which the 

 soil is superincumbent, consists of hornblende in small crystals, with 

 portions of quartz and some particles of calcareous spar. There is 

 probably also felspar, but, owing to the minute nature of the ingre- 

 dients of which the rock consists, it is difficult to discriminate the 

 substances with the eye. The analysis of the rock and soil has been 

 repeated each twice : — 



Soil. Greenstone. 



Specific gravity 2"91. 



I. II. I. II. 



Silica 5000 49-70 5020 51-20 



Phosphate of iron 6-10 6-66 2-00 2-04 



l-16\ 



)-83/ 



Lime. 2-64 3-50 9-12 8-76 



Magnesia and some potash 4*20 4-31 10-40 9*66 



Soluble salts 1 '63 



Organic matter 10-69 



Water 500 2-00 1*50 



Peroxide of iron 14-04 14-16 \ ^^ .^ 20*66 



Alumina 5-60 5-83/ ^° ^" 630 



100-00 100-12 100-12 



The large amount of magnesia in the rock obviously belongs to 

 the hornblende, the predominating constituent of the rock. 



Limestones. — The experiments made in the Glasgow laboratory 

 have proved the existence of phosphoric acid in the Irish limestone 

 in minute quantity, but in a somewhat greater amount than in the 

 English chalk, thus establishing chemically the parallelism of these 

 two rocks in a geological point of view. The determination of this 

 fact was conducted by Mr. John Thomson, M.A., in a most satis- 

 factory manner. Limestone from Ireland, which is employed abun- 

 dantly at Glasgow and on the Ayrshire and Wigtonshire coasts, was 

 examined and compared with chalk from Cromer on the coast of 

 Norfolk. The results were as follows : — 



Phosphoric acid in Cromer chalk . 0-77 per 1000 grains. 

 Irish limestone . 0-905 



Scottish Magnesian Limestone. — I requested my pupil, Mr. James 

 G. Stevenson of Jarrow, Shields, to examine the magnesian lime- 

 stone of Sunderland for phosphoric acid, but we could not detect a 

 trace of it in 1500 grains. We then turned our attention to the 

 magnesian limestone of Berwickshire, as found on the Tweed be- 

 tween Kelso and Coldstream, and formerly burned at Hadden, and 

 which I had found some years ago to possess the following composi- 

 tion: — 



