232 Geological Society : — 



tain the author's reputation for sound and dependable practical 

 instruction ; and we have no hesitation in recommending it to all 

 students of chemistry who wish to acquire a good all-round know- 

 ledge of the principles and methods of quantitative analysis. The 

 first part of the volume is devoted to exercises in weighing and 

 measuring, the fundamentals of quantitative work. The next sec- 

 tion gives a series of exercises in analytical methods, the examples 

 being well chosen, and sufficiently varied to give the student a 

 broad grasp of quantitative analysis. The third section treats of 

 organic analysis, and the fourth section of gas analysis, in con- 

 nexion with which will be found some very useful exercises. The 

 next section is devoted to a series of promiscuous exercises in the 

 application of the knowledge derived from the previous parts of 

 the work to the analysis of certain special things likely to be met 

 with in the course of practice ; such as sea-water (upon which the 

 author is an authority), Stassfurth Potash Salts, Cast Iron, Super- 

 phosphate, Guano, Milk, Butter, Soap, &c. The volume concludes 

 with some useful notes. We have no doubt that Prof. Dittmar's 

 work will soon find place among the recognized working manuals 

 used in our laboratories. 



XXIII. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from vol. xxv. p. 521.] 



May 23, 1888.— W. T. Blanford, LL.D., F.B.S., President, 

 in the Chair. 

 ^PHE following communications were read : — 

 -■- 1. " On the Spheroid-bearing Granite of Mullaghderg, Co. 

 Donegal." By Frederick H. Hatch, Ph.D., F.G.S. 



This paper deals with a remarkable variety of granite which may 

 be compared with the well-known orbicular diorite or Napoleonite 

 of Corsica. According to Mr. J. B. Kilroe, of the Geological Survey 

 of Ireland, who first discovered this interesting rock, the concre- 

 tionary balls occur in close juxtaposition in a mass of granite of 5 

 or 6 cubic yards in size. They have not been found in any 

 other portion of the granite area. 



The author first gave a detailed description of the microscopic 

 structure of the normal granite. It is a coarse-grained rock, com- 

 posed essentially of quartz, orthoclase, microcline, oligoclase, greenish 

 hornblende and black mica. Sphene is an accessory constituent. 

 Since it contains no white mica, the rock belongs to that subdivision 

 of granite which has been termed granitite. A description of the 

 spheroidal bodies was then given. The balls are somewhat flattened, 

 the greatest diameter being, in one case, 4 inches, the smallest 3. 

 Each ball consists of two distinct parts, a pinkish central portion 

 (the nucleus) and a dark-coloured peripheral or zonal portion (the 

 shell). The nucleus consists of an irregular granitic aggregate of 

 oligoclase felspar with a little interstitial quartz. The peripheral 

 shell is composed chiefly of oligoclase, but also contains abundant 



