( 2G5 ) 
CORKESPONDENCE. 
Eeoent Works on the Diatomace^, and on Objectives. 
To the Editor of the ' Monthly Microscopical Journal.'' 
Denstone, Ashbouene, March 29, 1875. 
Sir, — I am desirous to bring under the notice of the readers of the 
* Monthly Microscopical Journal ' the two following works which have 
recently come into my hands : (1) Dr. J. Schumann's ' DiatomacesB 
of the High Tatra,' * and (2) Otto Miiller's ' Eecent Microscopic 
Objectives Compared.' f 
Dr. Schumann's pamphlet is, beyond all dispute, the most pro- 
found work the world has yet seen on the application of the micro- 
scope to DiatomacesB, — and has no second. The most cursory glance 
will convince anyone that the writer is thoroughly competent to speak 
with authority on all the subjects he treats of. 
Before Dr. Schumann's book reached me, and while I knew it 
only by reputation, it was on my mind to translate it, or, at least, 
to abbreviate it for this Journal ; but an inspection of the work 
itself soon showed me the impracticability of such a scheme. The 
most valuable portions — those wherein he sets forth in exact mathe- 
matical formula3 the relation of the lines to each other, and the 
principles he deduces therefrom (pp. 18-26), and the rationale and 
estimate of errors of observation (pp. 30-35) — admit of no fair abbre- 
viation. I will content myself, therefore, with extracting only two of 
his remarks, out of many, that diatom-life, so far at least as the High 
Tatra is concerned, ceases at an elevation of 7802 Vienna feet, though 
Ehrenberg speaks of some as foimd on Mount Rosa at an elevation of 
14,284 feet ; further, that the structure of the frustule and the close- 
ness of the lines depend on the elevation above the sea level (pp. 1, 
38, 39, 85-94), and that consequently the size of the frustule 
diminishes, and the number of the lines in a given space increases, in 
proportion to the increase of elevation at which specimens of the same 
diatom may be found, and that the width of the lines diminishes about 
T3^wo 0" ^ Paris line for every 600 feet of elevation (p. 93). 
As the next best thing to a complete translation of Dr. Schumann's 
pamphlet I could wish much to see his four plates with their ex- 
planations (pp. 101, 102) reproduced, photographically, if possible, 
in the pages of this Journal : they are perfect marvels of skill and 
delicacy. In this connection I may refer those who are familiar with 
the appearance of Amphipleura pellucida, when perfectly resolved, to 
Dr. Schumann's drawing of that diatom (plate ii. fig. 19). I would 
also here publicly thank Dr. Emil von Marenzeller, Secretary to the 
* K. K. zool. botan. Gesellschaft in Wien,' for his kindness in sending 
* 'Die Diatomeen der hohen Tatra,' von Dr. J. Schumann. Wien, 1867. 
t * Vergleichende Untersuchungen neuerer Mikroskop-Objective,' von Otto 
Muller. Berlin, 1873. 
