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SCIENCE-GOSSIP. 



Sections from Mountain Limestone. — Of all 

 the sedimentary rocks forming the crust of the 

 earth none have been so fully investigated as the 

 carboniferous, owing to the importance of coal and 

 limestone to an industrial country like England. 



Fig. i. — L. portlocki (Horizontal Section 



One of the most striking features of the mountain 

 limestone is the wonderful perfection, both of 

 symmetry and detail, in which nature has preserved 

 through such a long period the organic remains of 

 which it is composed. In some of the corals, the 

 spines of Echini and Foraminiferse, indeed, the 

 calcareous remains are as sharp and clear in 

 character as in recent types. Visitors to museums 

 must often have been struck with this fact in 

 examining the shells, corals and other organisms of 

 which it is built up. If, however, they find this to 

 be the case with the unassisted eye, how much 

 more is it so when the help of the microscope tells 

 the story of their composition and structure ? 

 Many are familiar with the fossil corals, Lithostro- 

 tion basaltiformis and other species of this genus. As 

 an instance of the interest attaching to their closer 

 examination I submit photo-micrographs of Lithos- 

 trotion portlocki x 15 dia., fig. 1 being a horizontal 

 section cut through a mass, which reveals the star- 

 shaped corallium very distinctly. The coralites 

 vary somewhat in size, are prismatic in shape, and 

 united by their thin outside walls. The chalice is 

 divided into from twenty-two to thirty-six septa, 

 very unequally developed, thin, slightly flexuous, the 

 principal ones extending almost to the columella, 

 which is compressed and prominent. Fig. 2 is a 

 vertical section from the same piece, and shows 

 that in the exterior zone of the coralites the 

 vesicular septa form two or three longitudinal 

 series, and are much inclined inwardly ; that the 

 tubulse are well developed, raised centrally and 



divided exteriorally. The width of the coralites is 

 about a quarter of an inch. The specimen from 

 which they were cut is from the Peak district of 

 Derbyshire. In the volume of the Palaeontological 

 Society for 1852, will be found H. Milne Edward's 

 monograph of the fossil corals of the permian and 

 mountain limestone, with the beautiful plates he 

 prepared. This species, though not so widely 

 distributed as L. basaltiforme, has been found 

 at Castleton, Bristol, Craigbenayth, Wellington, 

 Corwen and Llangollen, in North Wales, and, 

 according to Col. Portlock, at Kildress, and at 

 Kesh, in Ireland.— W. W. Midgley, F. R. Met. Soc, 

 Museum, Bolton. 



Photography in Colours. — To succeed in 

 obtaining the colours of nature in a photograph, 

 or photogram as some would have it, is the desire of 

 every photographer, amateur or professional. Mr. 

 F. E. Ives, of Philadelphia, has succeeded by his 

 system of composite heliochromy in giving us 

 coloured pictures which can be viewed on the 

 screen. Now Dr. J. Joly, of Dublin, has obtained 

 as good effects as Mr. Ives did, without a tithe of 

 the trouble or expense. At the Royal Society's 

 Conversazione, on June 12th, Dr. Joly showed 

 some of his colour photographs, which are a 

 realization of composite heliochromy in a single 

 image. The method of composite heliochromy 

 requires three images superimposed by projection. 

 In these photographs the colour analysis and 

 synthesis are carried out in the one image. The 

 colours are the natural colours as they registered 

 themselves upon the plate, and in no case altered 

 after reproducton. The specimens shown are first 

 attempts, produced with rough apparatus. The 

 grained appearance of the image is avoidable with 

 proper appliances. The process of taking and 

 reproducing these photographs differs in no way 

 from ordinary photography upon the dry plate, 

 save that the sensitive plate is in the camera 



. — L. portlocki (Vertical Section) 



exposed behind a screen lined in particular colours. 

 The positive is subsequently viewed through a 

 screen lined with three other colours ; the three 

 "fundamental colours," which upon the three- 

 colour theory of vision are supposed to give rise to 

 all our colour sensations. 



