1 84 



SCIENCE-GOSSIP. 



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GEOLOGY 



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CONDUCTED BY EDWARD A. MARTIN, F.G.S. 



To whom all Notes. Articles and material relating to Geology, 

 and intended for Science-Gossip, are, in the first instance, 

 to be addressed, at 6q, Bensham Manor Road, Thornton Heath, 



Geological Education. — In conducting these 

 columns of geological gossip, it has been my 

 endeavour to place the science in as pleasant a light 

 as possible to those who are not geologists, in 

 the hope that geology, which still lacks workers in 

 everj- natural history society, may attract those 

 who have as yet not felt the inspiring influence 

 which it breathes. This journal is always open to 

 record the results of original research or discovery, 

 but I am anxious that our notes should have an 

 educational value, and that they should do some- 

 thing towards getting rid of the feeling of apathy 

 towards things geological, which is so frequently 

 found in scientific societies. We may recall with 

 pleasure the remarks made by Professor Logan 

 Lobley, at Croydon, last June, now brought to 

 mind by the issue of the " Report and Transactions 

 of the South-Eastern Union of Scientific Societies, 

 for 1S9S " : " Some blame is deserved, I confess, by 

 the geological world itself, which is too much 

 inclined to hide its light under a bushel and to rest 

 content with its own acquirements, without doing 

 much for the spread of its enlightening science. 

 I have had much personal experience of this 

 apathy against which I have had to contend, for, 

 clearly seeing the high educational value of 

 geology, the chief occupation of my life has been 

 the dissemination of geological knowledge." 



Geological Lantern Slides. — The report of 

 the recent Croydon Congress of the South-Eastern 

 Union shows that a series of seventy-eight lantern 

 slides have been got together, illustrative of the 

 Upper Greensand, Gault and Lower Greensand of 

 the south-east of England. These are in circula- 

 tion, and can be borrowed on application to Mr. 

 H. E. Turner, B.Sc, 2, Bouverie Street, West 

 Folkestone, who will also lend a written lecture, 

 which he has prepared to illustrate the slides. 



Photographers and Geologists. — The neces- 

 sity of an amicable plan of working between 

 geologists and those members of local societies 

 who are photographers only, deserves very great 

 emphasis. We have all heard of the photographer 

 who declined to waste a plate on a section which 

 failed to appeal to him from a point of view of 

 beauty. Geological sections are not always 

 picturesque, but those which are the less covered 

 with vegetation and other attributes of beauty are 

 often the most valuable of any. 



Lantern and Microscopical Slides. — I have 

 had considerable experience of Mr. J. Hornell's 

 photographic lantern slides, and have pleasure, 

 therefore, in calling attention to his excellent cata- 

 logue, which has just come to hand, of slides and 

 biological preparations. Materials from the Jersey- 

 Biological Station may be relied on for trust- 

 worthiness, at reasonable cost. 



Light and Heat of the Sun. — The question 

 is frequently raised as to how long the .sun has 

 continued to give out light for the illumination of 

 the earth. It is a question which must always 

 interest geologists, and as these are now apparently 

 willing to take their facts in such matters from the 

 physicists, it is well to note that Thomson and 

 Tait calculated that it may have illuminated the 

 earth for 100 millions of years, but certainly not 

 for 500 millions of years. If the earth were 

 suddenly stopped by an obstacle, the earth would 

 emit at once eighty-one times the heat which the sun 

 emits in one day. The earth would fall in towards 

 .the sun, and in the collision the sun would, in a 

 few minutes, emit as much heat as it now does in 

 ninety-five years. 



Tasmanian Igneous Rocks. — In a paper on 

 "The Igneous Rocks of Tasmania, "read by Messrs. 

 W. H. Twelvetrees and W. F. Petterd before the 

 Australian Institute of Mining Engineers, the 

 authors point out that field-geology in Tasmania 

 has hitherto resulted in describing the massive 

 rocks simply as granite, greenstone and basalt. A 

 more minute study convinces the investigator that 

 he has here to deal with what is really an epitome 

 of the world's eruptive rocks. The question of 

 classification receives a good deal of attention. 

 Harker has divided the igneous rocks into Plutonic, 

 Intrusive and Volcanic, i.e. according to their age, 

 while Geikie, Hatch, Rutley and Teall adhere to 

 the chemical classification. The authors adopt 

 Rutley's scheme, which is of so useful a nature as 

 to tempt me to print it here. 



5^0 



I Peridotite 

 Plutonic Granite Syenite Diorite Gabbro - Pyroxenite 



( Hornblen- 

 dite 



9> 



in 5 



H - 5 

 OWR. 



W o- ° 



.2"C 



dS55 5 



u; O 

 < o^ 20 



. 





t-,6 









Intrusive Elvau 



'Ortho- Plagio- ] 



clastic clastic [ ^ , ..„ „. 

 Lampro- Lampro- f Dol «ite Picnte 

 phyre phyre 1 



Effusive Rhyolite Trachyte Andesite Basalt 

 Glassy 



Picrite- 

 porphyrite 

 Obsidian Trachyte Andesite Tachylyte — 

 Glass Glass 



The only really acid glass in the island is found in 

 the buttons and bolts of obsidian met with in tin- 

 and gold-bearing drifts, but which have indisputa- 

 bly come from an outside source. They are found 

 all over Australia, at Java and Billiton, often 

 hundreds of miles from all volcanic rocks. No 

 satisfactory theory as to their origin has been 

 promulgated, although Dr. Verbeek (Geol. Sur of 

 Java) suggested they were showered on the earth 

 from lunar volcanoes. However that may be, it is 

 regarded as certain that these lava bombs of late 

 Tertiary age came from no Tasmanian crater. 



Septaria at Honor Oak Park. — A layer of 

 septarian nodules in London clay has been 

 exposed by the workmen at the back of the up-side 

 platform at Honor Oak Park Station, London, 

 Brighton and South Coast Railway. The line is 

 here in a deep cutting, and the layer must be about 

 twenty feet from the natural surface. It is quite 

 horizontal, and consists of nodules varying from six 

 inches to a foot in length, and is on a level with the 

 platform. 



