74 Geological Society : — 



attention was called to a statement by Sir W. Armstrong, to the 

 effect that Mr. Siemens had suggested as an explanation of the 

 otherwise anomalous advantage of forcing air into the boiler of a 

 steam-engine, that the air may prevent, in a great measure, the 

 condensation at the surface of the cylinder. It would thus seem 

 that Mr. Siemens has already suggested the probability of the fact 

 which is proved in this investigation. I am not aware, however, 

 that any previous experiments have been made on the subject, and 

 therefore I offer these results as independent testimony of the cor- 

 rectness of Mr. Siemens's views as well as of my own. 



y Great Oolite. 



► Inferior Oolite. 



GEOLOGICAL SOCIETY. 

 [Continued from vol. xlvi. p. 329.] 

 February 5, 1873.— Warington W. Smyth, Esq., F.R.S , Vice- 

 President, in the Chair. 

 The following communication was read : — 



1. " On the Oolites of Northamptonshire. — Part II." By Samuel 

 Sharp, Esq., E.S.A., F.G.S. 



In the first part of this memoir the succession of beds in the 

 neighbourhood of Northampton was shown to be as follows : — 



Clay.... 



White Limestone 



Clay with Ferruginous Band . 

 (" Upper Estuarine ") . . . 

 Line of Unconformity. 



f Sand with Plant Bed 



Northampton I (" Lower Estuarine ") . . . 



Sand .... 1 Variable Beds 



[ Ironstone Beds 



Upper Lias Clay. 

 The Great Oolite limestone of this section has been confounded, 

 even up to the present time, with a limestone (frequently Oolitic) 

 which occurs between Kettering and Stamford, is prevalent about 

 the latter town, extends through Kutland and Lincolnshire (where 

 it attains a thickness exceeding 200 feet) and into Yorkshire, 

 which limestone has been distinguished by Mr. Judd as the " Lin- 

 colnshire limestone." The object of the author was to show that 

 these two limestones were distinct, and that while the former was of 

 the Great Oolite period, the latter as certainly belonged to the 

 Inferior Oolite ; and in citing evidence in proof of this position upon 

 stratigraphical and palaeontological grounds, he gave a general ac- 

 count of the geology of the northern division of Northamptonshire, 

 illustrating his description by the exhibition of numerous fossils 

 gathered from the various beds and localities referred to. 



Between Northampton and Kettering, the Great Oolite limestone 

 is the surface rock ; and intersecting valleys upon that line, and the 

 escarpment of the Ise valley, a mile east of Kettering, exhibit this 

 sequence of beds : — 



Great Oolite { {? meBto " e / '. „ 



I Upper Estuarine Clays. 



