PETROLOGY. 201 



account of the microscopic structure and relations of some of the typical 

 Saxon diabases. The general conclusions are : — 1. Diabases may be 

 divided into two groups : Diabase composed of plagioclase, augite, 

 titanic-iron, magnetite, pyrites, apatite ; and Quartz diabase, a ciystal- 

 liiie mixture of plagioclase, augite, quartz, magnesian mica, titanic iron, 

 magnetite, pyrites, apatite. 2. The micro-structure of these groups is 

 distinctly crystalline. 3. The eruptive origin of diabases is proved by 

 their fluxed structure. 4. The plagioclase is always oligoclase. 5. 

 The augite and magnesian mica are converted by alteration into viri- 

 dite. 6. The magnetite is partly of secondary origin, and results from 

 the alteration of augite and magnesian mica. 7. The alteration of the 

 magnetite gives rise to hematite and liraonite. 8. The pyrites is a 

 subsequent product, also the limonite, and probably the specular iron 

 ore. 9. The quartz is either a normal component or may be of secon- 

 dary origin. 10. The calcspar is always of secondary origin. F. li. 



Dawkins, W. B. Observation on the Rate at which Stalagmite is 



being accumulated in the Ingleborough Caves. Kep. Brit. A.ssoc. 



for ] 873. Sections, p. 80. (See also Proc. Manchester Lit. and 



Phil. Soc. Feb. 1873.) 



The observations go back to 1839 (those of that date having been 



made by Mr. J. Farrar), and they show that the boss of stalagmite 



known as the " Jockey Cap " is increasing at the rate of -2946 of an 



inch per year. At this rate 20 feet of stalagmite might be formed in 



1000 years. W. T. 



Dewalqite, G. E-apport sur une memoire envoye au concours de la 



classe dcs sciences do 1874, en reponse a la question suivante : 



Faire connaitre^ notamment au point de vue de leur composition, 



les roclies plutoniennes, ou considerees comme telles, de la Belgique et 



de VArdenne frani^aise. [Composition of plutonic rocks of Belgium 



and the French Ardennes.] Bull. Ac. roy. Belg. 2 ser. t. xxxviii. 



no. 12. 



The rocks described are quartzose diorite of Quenast and Lessincs, 



gabbro (hypersthenite of Dumont) of Hozemont, porphyroids of Fan- 



quez, Rebecq-llognon, and Pitet, arkoses, quartzose porphyry of Spa, 



quartzose diorite of Lembecq, and rocks of the French Ardennes. The 



paper reported on is by Messrs. de la Vallee-Poussin and Renard, and 



will be published in the ' Memoires Couronnes.' G. A. L. 



DoELTER, C. [Eruptive Rocks of Transylvania.] N. Jahrb. Heft 3, 

 pp. 275, 276. 



Gives a summary of the results of studies of these rocks, especially 

 of the melaphyres and andesites ; the former are Jurassic, the latter 

 Tertiary. The andesites contain plagioclase, which in some cases is 

 andesine, in others labradorite. F. AV. R. 



. Die Trachyte dcs Siebenbiirgischen Ezgcbirges. [Trachytes 



