Reviews — Whitaker's Geological Model of London. 513 



in. — The American Association for the Advancement of Science ; 

 August 20th, 1873. Portland, Maine. 



Notes on the Fructification of Sigillaria. — At the meeting of 

 the American Association in Portland, Principal Dawson exhibited 

 and described a specimen of Sigillaria from Cape Breton, ex- 

 hibiting zones of marks of fructification on the stems and branches, 

 in the manner of ;S. elegans and S. Lalayana, and other species, to 

 which the species in question, S. Loriuayana, is closely allied. He 

 pointed out that these fruit-scars are really modified leaf-scars, and 

 that they could not have borne strobites or modified branches, but 

 may have produced single nuts of the nature of Trigonocarpa, or 

 flattened racemes of such fruits like Trigonocarpum racemosum, or 

 some Antholithes, which seem to be modified leaves with marginal 

 fruits, structurally resembling the fertile leaves of Cycads. These 

 points will be more fully brought out in a forthcoming Keport of 

 the Geological Survey of Canada. They confirm the views already 

 stated by the author in his " Acadian Geology," and were supported 

 in the discussion by facts from the Coal-fields of Ohio, stated by 

 Dr. Newberry, and shortly to be published by him in the Eeports of 

 the Survey of that State. 



I^E^V^IIE^W^S. 



Whitaker's Geological Model op London. 



UNTIL within the last twelve months, the work of the Geological 

 Survey in connexion with the surface geology of the London 

 district was unknown to the world at large. The nature of the 

 ground at the surface in any given district of the metropolis and 

 its suburbs, the range and thickness of the loams, gravels, and 

 superficial clays, and the questions of hygienic geology connected 

 with ^ them, were only to be settled by the outside world in an 

 empirical manner, unless the excellent maps and sections by Mr. 

 Mylne gave the desired information. The principle upon which 

 the Survey work has been conducted could hardly be expected 

 to be in advance of the age, and hence, with one exception, the 

 maps of the London district which we have hitherto had have only 

 represented the so-called solid geology of the area. London has 

 suffered largely from this curious division of labour. Until the 

 last year there was no delineation of those important surface ac- 

 cumulations of marine and fluviatile material, varying from ten to 

 twenty feet in thickness, which have such an enormous spread about 

 London, and largely determine the sanitary character of the area, 

 whilst they are also connected with the foremost geological 

 questions of the present day. Within the last few months, however, 

 and for the first time, a complete representation of the geology of 

 London, with all the aids of colour and relief contour, has been 

 produced under the auspices of the Survey. A large block-model, 

 showing both the superficial and solid geology of the metropolis, has 

 been placed in the Museum of Practical Geology in Jermyn Street. 



VOL. X. NO. CXIII. 33 



