636 



NATURE 



[February 4, 191 5 



between Abereiddy and Abercastle (Pembrokeshire). 

 The stratigraphy and structure of the greater part of 

 the district is described for the first time. Abereiddy 

 itself has been, since the time of Hicks, a type-locality 

 for the Llanvirn Beds. It has been found that the 

 Ordovician rocks of the district do not succeed one 

 another in a simple upward sequence, but that they 

 have been thrown into great folds and sometimes even 

 overfolded. The limbs of the folds increase in steep- 

 ness as the pre-Cambrian massif is approached. This 

 folding brings up strips of Cambrian rocks, the pre- 

 sence of which on the North Pembrokeshire coast was 

 previously unsusp>ected. There is a complete sequence 

 of Ordovician rocks from near the base of the Arenig 

 Series to high up in the Glenkiln Group. 



Linnean Society, January 21.— Prof. E. B. Poulton, 

 president in the chair. ^ — W. J. Dakin : Structure 

 and fauna of the Abrolhos Islands. Percy Sladen 

 Trust Expedition. The islands are situated 40-50 

 miles off the coast of West Australia. They are 

 interesting because of the almost complete lack 

 of knowledge concerning the marine fauna of that 

 part of the world. In addition, however, they possess 

 many peculiar features of their own. Although they 

 are coral islands (the most southern in the world), 

 the land fauna is decidedly continental and indicates 

 a comparatively recent connection with the mainland 

 of Australia. Again, although the coast is only forty 

 miles east of the islands, one has to travel some 

 hundreds of miles north of the latitude of the Abrolhos 

 to find a marine fauna on the coast with such tropical 

 characters. The collections have not yet been worked 

 out, but not the least interesting of the discoveries is 

 a new species of Enteropneusta, Ptychodera pelsarti, 

 closely allied to varieties of Pt. flava. This is the first 

 Enteropneust known from the West Coast of Australia. 



Institution of Mining and Metallurgy, January 21. 



Mr. Bedford McNeill, past president, in the chair. — 

 J. A. L. Henderson and W. H. Henderson : Inflam- 

 mable natural gas as an economic mineral. The 

 authors set out to show that natural petroleum-gas 

 is the only inflammable natural gas of economic 

 value, in its two divisions of "dry" or gas-well gas, 

 and "wet" or "casing-head" gas, which is chiefly 

 produced from oil wells. The former is of chief com- 

 mercial importance, as it is capable of direct use for 

 heating, power, and lighting purposes as it comes 

 from the well. The occurrence of natural petroleum 

 is co-extensive with that of petroleum, though the 

 reverse is not always true, as is shown by the relative 

 acreages of gas and oil fields in the United States in 

 191 1, which were 11,132,642 and 8,322,862 respec- 

 tively. The greatest and most extensive natural gas 

 deposits of economic importance, so far as known, 

 are found in the older, drier, and more consolidated 

 porous sedimentary rocks from the Cretaceous down- 

 ward. In the United States the industry has devel- 

 oped to such an extent that in 19 13 the value of 

 natural gas produced almost equalled that of the 

 gold produced. Natural gas 'has within the last ten 

 to fifteen years become a formidable rival to petroleum 

 in output, and even in value, despite the enhanced 

 prices that the oil has commanded in recent years. 

 In addition to the gas production of the United 

 States, which easily stands first, the authors direct 

 attention to the occurrences in Canada, Russia, 

 Galicia, Italy, Transylvania, and even in England.— 

 J. Cooli : Investigations in ore milling to ascertain 

 the heat developed in crushing. As the result of care- 

 fully conducted experiments with an electrically driven 

 stamp mill the author established the following data : 

 Of the E.H.P. supplied to the motor only 76 per 



NO. 2362, VOL. 94] 



cent, was apparently stored in the raised stamp; 

 the ore crushed was raised in temperature an average 

 of 48° C, while the wat^tr used was raised an 

 average of 0438° C. Of the actual E.H.P. put into 

 the motor, practically 61 per cent, was returned as 

 heat in the pulp. Of the energy which reached and 

 was stored in the lifted stamp, practically 80 per 

 cent, was returned as heat in the escaping pulp. In 

 the latter case the author allocates the remaining 

 20 per cent, unaccounted for as heat to (a) loss by 

 friction of the guides, (&) loss in sound and vibration, 

 (c) loss in radiated heat, and (d) the larger proportion, 

 loss due to the energy with which the pulp is 

 delivered through the screens. The test was borne 

 out by the fact that the screens had in places a per- 

 ceptibly higher temperature than the pulp. The 

 author asks : Is the energy used in tearing the ore 

 particles asunder entirely returned as heat, and do 

 some electrical phenomena exist? 



Mineralogical Society, January 26. — Dr. A. E. H. 

 Tutton, president, in the chair. — S. Kozu : The dis- 

 persion of felspar. By the most refined methods the 

 dispersions in the three principal directions were deter- 

 mined for various members of the felspar group. — 

 F. P. Mennell : Note on the colour of some alluvial 

 diamonds and of pyrrhotite. The colour, usually 

 green, of the diamonds in the gravels of Somabula, 

 Rhodesia, is superficial, and probably due to infiltra- 

 tion, presumably of iron salts, while the stones were 

 lying where they now occur. Pyrrhotite is tin-white 

 in colour when fresh. The cause of its rapid altera- 

 tion was discussed. — Prof. G. Cesaro : Crystals of 

 calomel from Spain. The crystals, which were pale- 

 yellowish in colour, imperfectly transparent, from 

 1-3 mm. in size, and displaying the forms 100, iii, 

 311, were most irregularly developed. — Prof. G. 

 Cesaro : General formula for the birefringence of a 

 crystal-plate in terms of the angles which its normal 

 makes with the principal optical axes. The approxi- 

 mate formula is obtained by supposing the mean index 

 of refraction to become infinite, while the differences 

 between it and the greatest and least indices remain 

 constant. — Prof. G. Cesaro : A numerical relation of 

 the sum of the symmetry-axes situated in the sym- 

 metr\-planes of a polyhedron. If N . A„, P . A,„ 

 Q . A, . . . are the axes of symmetry lying in the planes 

 of symmetry, then — 



4{Nn(n-i) + P/)(/)-i) + Qg(g-i) + . . .} + i=C, 



and the number of planes of symmetry is given by 

 X = i(C + i). 



Dublin. 

 Royal Irish Academy, January 11. — Rev. J. P. 

 Mahaffy, president, in the chair. — S. B. Kellelier : A 

 three-dimensional complex variable. Some properties 

 of expressions of the form P+Q9+R6^ where P, Q, R 

 are functions of three independent variables and 6^ 

 is equal to unity, but i-hO+6^ is not zero. — R. 

 Soutliern : Summary on marine distribution (Clare 

 Island Survey). This paper is in the nature of a 

 summary of the results obtained by the investiga- 

 tion of the marine fauna of the Clare Island area. 

 The nature of the coast-line and sea-bottom is 

 described, and the various types of habitat and the 

 associations of animals inhabiting them are discussed. 

 The distribution of the fauna from the geographical 

 point of view is then considered. Some observations 

 on the period of reproductive activity of various species 

 are included. A description of the hydrographical 

 results obtained in the course of the survey is given. 

 The total number of marine species of animals ob- 

 tained in the course of the survey is approximately 



