Miscellaneous. 157 



on many spots of our shores, the lower parts of the ripple-markings 

 often affording coarse sand and broken pieces of shells, so likewise 

 during the Silurian epoch we have circumstances prevailing, such as 

 to show that the sun bleached the empty shells and cracked the dry 

 mud on this ancient sea-beach as it does at the present time. 



The evidence of the occurrence of land in formations antecedent to 

 the carboniferous is exceeding rare, the deposits being exclusively of 

 a marine character ; and although this deposit at Reaberry Head 

 only affords marine remains, yet the circumstances under which it 

 occurs, and also the state of the fossils which are imbedded in it, 

 leave no doubt that the sea, at the period when this littoral deposit 

 was being formed, rolled over a shore which skirted some portion of 

 land then above the surface of its waters. And it is probable that this 

 land had its fauna and flora, which this withered shell-bed may pos- 

 sibly at some time afford us some knowledge of. — Robert Hark- 



NESS. 



On the Cell-membrane of Diatomaceous Shells. By J. W. Bailey. 

 If hydrofluoric acid is applied to recent Diatomaceae, the shell 

 soon dissolves, leaving distinct, internal, flexible cell-membranes re- 

 taining the general form of the shells. These may sometimes but not 

 generally be detected even in the fossil specimens. When present, 

 they materially interfere with the examination of the true nature of 

 the markings of the siliceous shell, and should be destroyed by nitric 

 acid and heat, before the hydrofluoric acid is employed, unless it is 

 desired to study the cell-membrane itself. There is a curious differ- 

 ence in the action of hydrofluoric acid of the same strength upon 

 specimens of fossil Diatomace&e from different localities. Some dis- 

 solve with even too great rapidity in an acid which is slow and tedious 

 in its action on other specimens. The Bermuda and Richmond 

 Tripoli, and some specimens of fluviatile origin resist the action much 

 longer than is usual with most specimens, whether they are recent 

 marine, or either recent or fossil fluviatile ones. This difference is 

 probably due to different degrees of hydration. -^Frorn Sillimarfs 

 American Journal of Science and Art, No. 33, May 1851. 



A Comparative Examination of the Objective Glasses of Microscopes 

 from Mr. Ross of England ; Mr. Spencer of America ; and M. 

 Nachez of Paris. By J. Lawrence Smith, M.D. 



Having had an opportunity, a short time since, while at Paris, to 

 examine the comparative merit of the lenses of these makers, it might 

 not be uninteresting to microscopists to know the result of my ex- 

 amination, particularly as it was made under peculiar circumstances ; 

 namely, by adapting alternately the objectives to the same mounting, 

 and regarding the same object under the same illumination. 



The glasses used were considered by their makers as among their 

 best. That made by Ross was in the possession of M. Rutherford of 

 U. S. Spencer's was owned by Dr. Burnet of Boston, and had just 

 been brought by him from Spencer. That of Nachez belongs to Dr. 

 Bigelow of Boston, now in Europe engaged in microscopic research 



