59 



ON THE MICEOSCOPICAL EXAMINATION 0¥ SOME 

 BEACKLESHAM BEDS. 



By T. Etipert Joi^es, E.G.S. 



In Yol. I of the ' Geologist,' at page 249, was published a paper 

 on the preparation of sands, clays, and chalk, for microscopical pur- 

 poses, under the heading of " Geological Manipulations ;" and, as 

 both pleasure and geological profit are to be obtained from the exact 

 examination of various fossil-bearing deposits, both as to their con- 

 stituents and their cod tents, I beg to offer you an example of the 

 results of such an examination of some tertiary beds from Brackle- 

 sham. These notes I have had by me several years, and their short- 

 comings are so great in some respects that I should not send them, 

 were it not that they may serve as a plan to some young care- 

 ful observers who might feel inclined to enter upon the strict exa- 

 mination of some definite series of fossiliferous strata. "What the 

 series under notice is deficient of, is a statement of the exact rela- 

 tionship of these several deposits, examiued nearly twenty years ago. 

 I received the materials at that time from a friend who was collecting 

 " Bracklesham fossils," — a term which will be more definite, now 

 that the Eev. 0. Eisher, E.G.S., has indicated the exact limits of the 

 Bracklesham formation.* 



The specimens were chiefly, I believe, from Bracklesham and 

 Selsea ; but some may have been brought from the Isle of Wight. 

 By the presence of certain fossils, however, in some of the deposits, 

 their exact place may probably be determined. However deficient 

 in these stratigraphical requirements the following account of the 

 deposits may be, they will serve the purpose here intended, namely, 

 to show young beginners what to look for in sands and clays. In- 

 structions have been already given as to how such materials are to 

 be examined, in the first volume, p. 249. 



The careful microscopical examination of a good series of succes- 

 sive deposits, in the way that we propose, cannot but be useful both 

 to the geologist and the palaeontologist. The conditions of deposit 

 will be elucidated by the proportions of fine and coarse materials in 

 the beds ; especially if these be traced along a considerable tract by 

 the examination of many samples of the deposit, through its varia- 

 tions from clay to sand (or vice versa), or in its changes from an 

 argillaceous or arenaceous to a calcareous condition. Such variations 

 are not always recognized with sufiicient exactness by the eye or by 

 the pocket-glass, and require mechanical, if not chemical, analysis; 

 recourse being had to the aid of acids in determining the relative pro- 

 portions of lime and other constituents. Except by careful separa- 

 tion in water, and patient sorting and picking, the minute shells and 

 other fossils cannot be obtained in anything like a fair average ; and 

 year by year the Eoraminifera, Entomostraca, Bryozoa, and the small 



* See Report of the Geological Society's Proceedings, Dec. 4th, 1861. 



