, 
ACKNOWLEDGMENTS TO CORRESPONDENTS, FRIENDS 
AND STRANGERS. 
Remarks.—This method of acknowledgment has been adopt- 
ed, because it is not always practicable to write letters, where 
they might be reasonably expected; and still more difficult is it 
to prepare and insert in this Journal, notices of all the books, pamph- 
lets, &c., which are kindly presented, even in cases, where such no- 
tices, critical or commendatory, would be appropriate ; for it is often 
equally impossible to command the time requisite to frame them, or 
even to read the works; still, judicious remarks, from other hands, 
would usually find both acceptance and insertion. 
in public, it is rarely proper to advert to personal concerns; to 
excuse, for instance, any apparent neglect of courtesy, by pleading 
the unintermitting pressure of Jabor, and the numerous calls of our 
fellow-men for information, advice, or assistance, in lines of duty, 
with which they presume us to be acquainted. 
The apology, implied in this remark, is drawn from us, that we may 
not seem inattentive to the civilities of many respectable persons, au- 
thors, editors, publishers, and others, both at home and abroad. It 
is still our endeavor to reply to all letters which appear to require an 
answer; although, as a substitute, many acknowledgments are thade 
in these pages, which may sometimes be, in part, uo Sgr aa 
Eds. ° 
SCIENCE.—FOREIGN. 
On the composition of Chalk Rocks and Chalk Marl by invisible 
organic bodies, from the observations of Prof. Ehrenberg; with an 
appendix touching the researches of MM. Alcide and D’Orbieny ; ; 
by Thos. Weaver, sq., F. Ab Be, LA. &e: From 
the L. & E. & D. Phil. Mag. for May and June, 1841. London. 
Pamphlet, pp. 48. From the Author. 
Report of the Tenth Meeting of the British Association for the 
Advancement of Science, held at Glasgow, in August, 1840. 8vo, 
pp: om Published by John Murray, London. From the Asso- 
ciatio 
etaatititein of the Royal Society of Edinburgh. Vol. i pe 
second; pp. 359-754. From the Socie 
iety. oe 
Description of a series of Geological Models ; ier Sopwith, 
ee fone a assagatle tga rr A2eno+.D PP- Rhus: 
