274 Remarks on Mr. Henry Davis Paper. 



It follows that when a lens of ordinary glass makes balsam- 

 contact with the cover of a balsam-mounted object, the exposed 

 surface of the lens is to be regarded as the first refracting surface, 

 and the angle with which a pencil of light may emerge depends 

 upon the curvature of that surface, and has nothing to do with the 

 plane surface of the submerged cover. How much of the pencil 

 may be brought to a focus depends upon the succeeding lenses in 

 the combination. This is strictly true for glass and balsam, having 

 the same refractive index, and is nearly true in all practical cases, 

 even if water be substituted for balsam between the lens and 

 the cover. 



Eenel Keith. 



Remarks. By Mr. Wenham, V.P.E.M.S. 



After my final reply to Mr. Tolles was sent for publication, I 

 received a letter from my respected friend, Col. Woodward, cour- 

 teously inviting me to read the above before appearing in print, in 

 order that I might append my remarks. At the same time, I 

 am pleased that the settlement of the question should rest with 

 Col. Woodward, whose phraseology and demonstrations I am sure 

 to comprehend. As the proof, however, came to hand late, scarcely 

 leaving me time to consider all the points at issue, and without 

 any diagrams,* I prefer making my remarks in the next Journal. 

 I can only say at present that, after reading the article, I do not 

 see that there is much left to controvert, as Col. Woodward sub- 

 stantially corroborates my position, any apparent differences, pro- 

 bably arise from some statements that have been lost sight of 

 during this long and tedious correspondence. 



F. H. Wenham. 



V. — Remarks on Mr. Henry Davis' Paper " On the Desiccation 

 of Rotifers." By C. T. Hudson, LL.D. 



The alleged revival of Eotifers after a thorough drying has always 

 been a perplexing chapter in their natural history. Those who 

 have written on the subject have come to very different conclusions. 

 Some relate apparently trustworthy experiments in which Eotifers 

 have been subjected to the drying effect of a vacuum produced by 

 an air-pump and sulphuric acid, and to that of an oven heated to 

 200° Fahr., without losing their vitality. Other experimenters 

 equally trustworthy declare that, if the heating be carried some 

 degrees higher, the Eotifers do not recover ; while, of the authorities 

 who sum up the evidence, some say that Eotifers may be " com- 

 * Tlioy had been sent to tlie artist. — Ed. 'M. M. J.' 



