666 BEPOET— 1886. 



small crystals of an orange Yed, and still more rarely of a light yellow colour, 

 Barytes occurs somewhat plentifully at Snailbeach, and AMtlierite is also met with. 



The vein of barytes at Wotherton has been worked for sixty years. Mr. \V. 

 Yelland, who had charge of the mine a few j-ears ago, has supplied me with the 

 following particulars : — The lode is in some places upwards of twenty feet wide, 

 and is divided into two parts by a vein of greenstone, technically termed a ' horse ' 

 or rider. The rider is traversed by narrow bands of barytes. In some parts of the 

 lode the rider disappears altogether, or is very narrow. A boss of greenstone pro- 

 jects from the foot wall, and from this issue bands of stone traversing the lode in 

 an oblique direction, until they come in contact with the hanging wall. 



Cavities containing crystals occur in the lode, the cavities being filled with fine 

 clay of a bluish tint. Proceeding from one of the cavities, which was carefully 

 examined, were two thin fissures, also containing clay, and fi'om which on tapping 

 ■water ran out. The crystals j nst referred to by Mr. Yelland are particularly clear, 

 and exhibit many crystallographie forms, Mr. H. p. Miers, of the British 

 Museum, has examined these crystals (' Nature,' xxix. p. 29), and notes the follow- 

 ing forms : 101, 012, 110, 014, Oil, 100, 010, 001, 412, 212, 111, 232, 4-32, 214, 112, 

 034, besides two doubtful planes of the complicated symbols 15.1.15 and 19.1.18. 



Specimens illustrating the author's remarks were lent by Messrs. Waters and 

 Son, of Shrewsbury, by jMr. Dennis, Managing Director of the Snailbeach Mine, 

 and also by Mr. Job, of the same mine. These, together with others sent by Mr. 

 Jasper Moore, M.P., have been placed in the Natural History Room of the Exhi- 

 bition for examination. 



3. The Anorthosite EocJcs of Canada. Bij Frank D. Adams. 



This series of rocks has also been called the Upper Laurentian or Norian series. 

 The name anorthosite is perhaps preferable, as it refers to their distinguishing 

 characteristic as compared with the orthoclase rocks of tlie Lower Laurentian, viz, 

 the predominance in them of plagioclase or anorthose felspar. These rocks form 

 detached areas in the great Laurentian districts, and bear a strong resemblance in 

 part to the gabros and gabrodiorites of Scandinavia, and in part to the labradorite 

 rock of the same country. It is, however, by no means certain that the rocks of 

 the two countries are of the same age. At least nine of these areas are now 

 known to exist in Canada, and there is also one in the State of New York. In 

 addition to plagioclase, which generally predominates largely, these rocks contain 

 rhombic and monoclinic pyroxenes (including augite, diallage, hypersthene, and 

 probably enstatite), olivine, magnesia, mica, spinel (including both pleonaste and 

 picotite), garnet, iron ores, pyrite, and apatite. Orthoclase is seldom or never 

 found, except in veins cutting the anorthosite. Tlie hornblende, mica, and py- 

 roxenes are intimately associated and often intergrown, all of them sometimes 

 being found in the same thin section. Garnet occurs sparingly, and generally near 

 the contact of the anorthosite with the gneiss. When the olivine comes against 

 plagioclase it is always bounded by a double concentric zone, the outer zone con- 

 sisting of hornblende, and the inner, or that next to the olivine, consisting of a 

 pyroxene. While the iron ores associated with the Lower Laurentian gneisses are 

 g'enerally free from titanium, those associated with the anorthosite rocks are always 

 highly titaniferous ; a fact which makes the study of these rocks a matter of con- 

 siderable economic interest. The anorthosite varies a good deal in composition, 

 some areas, for instance, beuig rich in olivine, while others are destitute of that 

 mineral, and diflferent portions of even the same area often showing wide differ- 

 ences in this respect. The rock also shows a good deal of variation in structure. 

 It is rarely quite massive, frequently well foliated, but usually consists of a rather 

 coarsely crystalline ground mass through which are scattered irregular strings and 

 masses composed ot iron ore, bisilicates, and mica, as well as larger porphyritic 

 crystals of plagioclase. Even when it is tolerably constant in composition there is 

 generally a great variation in size of grain, coarse and fine alternating in rude 

 bands or rounded masses. In the case of some of the areas there can be but little 

 doubt that the anorthosite is eruptive ; in others, however, it seems to be inter- 



