460 



SCIENCE. 



[Vol. I., No. 16. 



bj' fusion, both b}' the study of natural and 

 artificial products, with a few apparent excep- 

 tions, which receive a special explanation. 



B_y a judicious combination of substances 

 and temperatures, the authors succeeded in 

 obtaining eleven distinct mineral associations, 

 almost exactlj' reproducing, even in the mi- 

 nuest details of structure, as many natural rock 

 types. 



These are as follows : 1°. Augite (oligoclase) 

 andesite, 2°. Augite {labrador) andesite, 3°. 

 Augite (anorthite) andesite (all produced b}' 

 single fusion at temperature No. 3) ; time three 

 days. 4°. Basalt. Two successive stages of 

 fusion were necessary to produce this rock. 

 Temperature No. 2 produced in fortj'-eight 

 hours numerous crj'stals of olivine embedded 

 in a glassj' matrix, which was altered into a 

 crj-stalline mass of labradorite and augite 

 microliths by being again subjected for an equal 

 length of time to temperature No. 4. 5°. Ne- 

 phelinite was produced in forty-eight hours at 

 temperature No. 4. 6°. Leucitite was obtained 

 after three days' fusion at temperature No. 2. 

 7°. Leucititephrite produced by double fusion 

 exactly like basalt. 8°. Llierzolite, 9°. Mete- 

 orites free from felspar, and 10°. Felspathic 

 meteorites, though quite successful so far 

 as the mineral associations were concerned, 

 showed certain variations from the natural 

 l^roducts in their structure. No synthesis was 

 perhaps so interesting as that of 11°. Diabase, 

 with the so-called ' ophitic ' structure. This 

 structure consists, as is well kuown, of irregu- 

 lar masses of pyroxene filling the spaces be- 

 tween the lath-shaped crystals of plagioclase. 

 It was found to be impossible to reproduce 

 this structure with oligoclase or labradorite, 

 on account of their comparatively low fusing- 

 point. Bj- means of a double fusion with an- 

 orthite, it was, however, successfull3' accom- 

 plished. 



Scarcely less interesting than these positive 

 results are the conclusions derived from the 

 authors' negative experiments. It was found 

 impossible to obtain the acid rocks, i.e., those 

 containing either quartz, albite, orthoclase, 

 muscovite, biotite, or amphibole, by purel}' 

 igneous fusion. These minerals either pro- 

 duced an amorphous mass, or passed into other 

 combinations giving rise to species alreadj' 

 obtained; e.g., hornblende, when melted, 

 crystallized as pyroxene. Thus the very im- 

 portant conclusion is reached, that the acid 

 rocks owe their origin to some other agenc}' 

 than simple fusion. 



Under the head of the sj'nthesis of minerals, 

 the authors' experiments in fusing mixtures 



of felspars are worthy of special notice as 

 being directly opposed to the now generally 

 accepted theory of Tschermak, that the triclinic 

 felspars form an isomorphous series. Fouqu6 

 and L^vy found it impossible to obtain cr3'stals 

 of Intermediate members, as only well-defined 

 microliths of either oligoclase, labradorite, or 

 anorthite, appeared, varying in their relative 

 proportions with the mixtures fused. Also of 

 especial interest are their artificial production 

 of felspars with lead, barium, and strontian 

 as bases. 



THE GEOLOGY OF NATAL. 



Natal. Department of mines. Report upon the coal- 

 fields of Klip River, Weenan, Umvoti, and Victoria 

 counties, together with tabulated statement of results 

 obtained from a series of trials of colonial coal upon 

 the Natal government railways. By F. W. North. 

 London, Harrison, pr., 1881. 1,66 p., (49) pL, 

 etc. f°. 



This report contains two maps, showing the 

 distribution of the coal-fields of the colony of 

 Natal, and a description of 72 sections occur- 

 ring in them, 70 of which are illustrated by dia- 

 grams. There are also two horizontal sections 

 given, — one from Buffalo River to the Dra- 

 kensberg Mountains, and the other from Buf- 

 falo River to Elands Laagte. 



Mr. North estimates the actual area of the 

 Natal coal-field, where he has found workable 

 coal-seams at the surface, at about 1,100 n 

 miles, situated entirel}- in Klip River count}'. 

 To this he adds 250 a miles for the region 

 between the Ingagani River and the Drakens- 

 berg Mountains, which he considers the coal 

 measures underlie. The workable seams vary 

 from 4 to 10 feet in thickness, and are of sev- 

 eral qualities. Assuming an average thickness 

 of 4 feet, and allowing a deduction of 50 per 

 cent for faults, worthless coal, and barren 

 ground, he estimates the whole at 2,073,000,- 

 000 tons, divided into, — 



Tons. 



Anthracite, similar to Gladstone . . . .518,400,000 



Semi-bituminous, similar to Walmesley, 518,400,000 



Bituminous, similar to Dundee coal- 

 fields and Lenox sections .... .518,400,000 



Free-burning bituminous coal of the 

 same character as No. 44 Crown 

 lands and Lenoxton, Newcastle . 518,400,000 



Total 2,073,600,000 



Mr. North considers these coals superior in 

 qualitj' to those of Cape Colon}-. A number 

 of analyses of them have been made by Dr. 

 Frankland and Dr. Hahn. There are also 

 many beds of iron ore: the one from Prestwick 

 is an intimate mixture of magnetic iron ore and 



