July 21, 1923] 



NATURE 



T17 



Optical Activity " ; Mr. H. Phillips (Battersea 

 Polvtechnic) for a thesis entitled " The Relation 

 between Chemical Constitution and Optical Rotatory 

 Power"; Mr. A. Brammall (Imperial College, Royal 

 College of Science) for a thesis entitled " The Mineral- 

 ogy, Structure, and Petrology of the Dartmoor 

 Granite"; Mr. H. Schofield (Imperial College, Royal 

 College of Science) for a thesis entitled " The Measure- 

 ment of Thermal and Combustion Efficiency of High 

 Speed Multi-Cylinder Internal Combustion Engines 

 by the use of a new Optical Indicator," and Mr. 

 R. L. Smith-Rose (Imperial College, Royal College of 

 Science and City and Guilds College) for a thesis 

 entitled " On the Variations of the Apparent Bear- 

 ings of Fixed Radio-Transmitting Stations." Ph.D. 

 {Engineering) : Mr. H. F. G. Letson (East London 

 College) for a thesis entitled " The Experimental 

 Determination of the Temperature Distribution, and 

 Calculation of the Thermal Stresses in a Diesel Engine 

 Cylinder Liner." 



Applications are invited for the William Julius 

 Mickle fellowship, of the value of at least 200/., 

 awarded annually to the man or woman resident in 

 London and a graduate of the university who is 

 deemed by the Senate to have done most to advance 

 medical art or science within the five preceding years. 

 Applications must reach the Principal Officer of the 

 University, South Kensington, S.W.y, by. at latest, 

 the first post of October i next. 



On July 27, the summer meeting of the University 

 of Oxford Delegacy for the Extension of Teaching 

 opens with an inaugural lecture by Sir Michael Sadler. 

 We have already referred to the excellent programme 

 which is being provided this year (Nature, May 19, 

 p. 688), which includes lectures on the functions of 

 universities, the economics of English country life, 

 and research in organic chemistry. Special railway 

 facilities are being offered for those desirous of 

 attending the meeting. Full particulars can be 

 obtained from the Secretary, University Extension 

 Delegacy, Examination Schools, Oxford. 



The jubilee celebrations of the Cambridge Uni- 

 versity Local Lectures began on Friday, July 6, with 

 a special Congregation for the conferment of honorary 

 degrees for distinguished service in the cause of 

 university extension, namely, the degree of LL.D. on 

 Sir Michael Sadler, Mr. R. G. Moulton of Christ's 

 College, and Mr. Albert Mansbridge, and the degree 

 of M.A. on Mr. G. P. Bailey, Mr. J. H. Fisher, and Mr. 

 Alfred Cobham. On the Saturday and Monday there 

 were meetings of a conference on extra-mural teaching. 

 Speeches at the conference emphasised the far-reaching 

 effects of the movement initiated in Cambridge by 

 James Stuart in 1873, which has spread not only 

 throughout the British Empire but to most of the 

 civilised countries of the world, attaining its greatest 

 and most various developments in the United States. 

 The speeches dwelt also on the value to extra-mural 

 lecturers of the stimulation they receive from 

 lecturing to (and being cross-examined by) adult 

 audiences, contrasting their eagerness with, and 

 perhaps exaggerating, the lethargy and " anxiety to 

 curb an exhibition of enthusiasm " of the normal 

 undergraduate student. In the opinion of the Master 

 of Balliol, those who are responsible for the further 

 development of the movement are at a parting of the 

 ways, and careful guidance will be needed if it is 

 not to suffer the usual penalty of success and become 

 absorbed in its own mechanism. Progress will 

 depend largely on co-operation between universities, 

 local authorities, and voluntary bodies. 



NO. 2803, VOL. I 12] 



Societies and Academies. 



London. 



Mineralogical Society, June 19. — Dr. A. Hutchin- 

 son, president, in the chair. — L. J. Spencer, with 

 chemical analyses by E. D. Mountain : New copper- 

 lead minerals from the Mendip Hills (Somerset). 

 Mendipite (2PbO . PbCl2), which occurs as crystalline 

 nodules in manganese-ore, is recorded from new 

 localities. Chloroxiphite (2PbO . Pb(OH)2 • CuCL) 

 as green monochnic blades resembling epidote, and 

 diaboleite (2Pb(OH)2 . CuCL) as bright-blue tetragonal 

 plates resembling boleite, both occur embedded in 

 the mendipite. Hydrocerussite (2PbC03 . Pb(OH).2) is 

 abundant, sometimes as large crystals {i.e. crystallised 

 " white lead "). Crednerite (CuO . MuaOj) forms fan- 

 like aggregates of thin plates. Pyromorphite was, 

 some centuries ago, evidently an important ore of 

 lead in the Mendips. Wulfenite and mimetite have 

 been found at Higher Pitts near Priddy. The various 

 minerals show progressive stages of alteration with 

 some well - marked pseudomorphs : mendipite — >■ 

 hydrocerussite — >cerussite ; chloroxiphite — >-hydro- 

 cerussite + malachite I — > cerussite + crednerite — >- 

 malachite II. — W. F. P. McLintock : On a petalite- 

 bearing rock from Devonshire. The well-known 

 aplite from Meldon in Devonshire develops in 

 certain parts of .the intrusion a soda-lithia phase 

 rich in the rare lithium-aluminium silicate, petalite. 

 This mineral, not previously known from Britain, 

 occurs as one of the final products of consolidation 

 of the aplite either in coarse-grained veins of pegmatite 

 associated with quartz, orthoclase, albite, a lithia- 

 bearing mica, tourmaline, and apatite, or as irregularly 

 shaped masses throughout the rock itself. The 

 petalite gives rise by decomposition to the pink 

 clay, montmorillonite, so well known from this 

 locality. Certain other veins, free from petalite, 

 are also present, the most interesting constituents 

 of the rarer types being prehnite, axinite, and a 

 pleochroic cordierite. The apatite in the aplite is 

 a pneumatolytic mineral occurring not only in the 

 rock as ophitic patches enclosing quartz and felspar, 

 but also impregnating certain xenoliths of peculiar 

 type. — A. Brammall and H. F. Harwood : The 

 accessory minerals of the Dartmoor granite. Tour- 

 maline, which is one of the minerals identified, 

 originated at two stages in the cooling history of 

 the intrusion : (i) pre-solidification — primary and 

 secondary ; (2) post-solidification — secondary. The 

 more severe and widespread pneumatolysis and the 

 lodes are referred to a post-solidification stage. — 

 Seitaro Tsuboi : (i) Optical dispersion of three 

 intermediate plagioclases. The principal refractive 

 indices, a, /3, 7, of {a) oligoclase from Hawke mine, 

 Bakersville, North Carolina, (6) andesine from 

 Maeyama, Shinano, Japan, and {c) labradorite from 

 County Down, Ireland, for light of 9 different wave- 

 lengths, and the optical orientations of the first and 

 the third of these felspars, for light of 5 different 

 wave-lengths (700, 644, 589-3, 535, 5o8-5mm) were 

 determined. (2) A dispersion method of determining 

 plagioclases in cleavage-flakes. The method is based 

 on the principle of H. E. Merwin's improved immersion 

 method. By means of a diagram a quick and exact 

 determination of plagioclases is possible. It is 

 applicable to small crystals such as are common in 

 rocks. — C. S. Garnett : The " toadstone-clays " of 

 Derbyshire. The olivine-dolerites (" toadstones ") of 

 Derbyshire undergo two types of alteration : (i) by 

 ordinary weathering to limonite or ochreous deposits ; 

 (2) in the absence of oxidising agents under a lime- 

 stone covering, they may pass through dolerite- 

 greenstone and " green-earth " to a greenish- white 



