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POPULAR SCIENCE REVIEW. 
advise the use of zinc white, in preference to white lead, as the latter turns 
yellow in the course of a month or two. I give the preference to vermilion 
or purple lake for the exterior ring, finishing with an interior ring of zinc 
white.” 
Mr. Wenham's Position as a Controversialist is admirably, and, we need 
hardly say, most tersely defined by himself in a contribution to the March 
number of the “Monthly Microscopical Journal.” For ourselves, w^e must 
certainly say he appears to have kept his temper throughout in the most 
admirable manner, and he has formed a very excellent comparison to some 
other gentlemen who shall be nameless for the present. Mr. Wenham 
says : — “The controversy was begun by myself three years ago ; I then dis- 
puted what I considered to be an erroneous theory, appearing in an essay 
illustrated by large diagrams, to prove an increase of aperture alleged to be 
obtained by immersion lenses,* and pointed out how rays were taken from 
wrong positions in impracticable constructions. The author of the essay 
referred to had merely carried the rays into imaginary front lenses, and there 
deserted them, regardless of their ultimate destination to a posterior conju- 
gate focus at the eve-piece. The subject has been kept up at intervals by 
correspondents, with whom I have still to deal. It is difficult to do this 
without exciting some degree of irritation, because the nature of such stric- 
tures implies ignorance of the laws of optics — a science which has long been 
so exactly defined that there should be no error of the passage of a ray 
through refracting surfaces. According to disposition, so do modes of con- 
troversy differ : perhaps my own is an obnoxious one. Let it be compared. 
Some always write in the first person singular, and reiterate their views as if 
to command belief, conceding no credit, and ignoring all replies except to 
those who favour their assumptions, with an air that says — 
1 1 am Sir Oracle, and when I ope my mouth let no dog bark ! ’ 
This scarcely brings forth fruit. I am always glad to exchange notions with 
practical working men, and to give my own in ordinary phraseology. Then 
there is discussion with a snarl, of which this aperture questions affords 
some examples. This is the least productive of any, for its main strength 
consists merely in picking out contradictions and anomalies of phrase ; 
science is tossed aside, and its cold reasoning avoided because it is not un- 
derstood, and abuse is mistaken for keen argument. Satire may appear in 
discussion, arising not from ill-temper, like the last, but it is apt to offend. 
I find it difficult to restrain the propensity at times, though quite aware 
how few can accept it. Again, there is the meek and amiable style, that can 
neither make or answer a strong objection, saying, 1 1 am sorry that I have 
disturbed you, gentlemen ; I will drop the question rather than disagree ! ’ 
This I cannot take credit for, but judging from the attitude of some of my 
opponents, it would seem as if I am a wolf amongst the lambs.” 
Two New NobeiTs Test-Plates have been received by Dr. Woodward, of 
America ; and although the fact was announced in the “ Quekett Club 
Journal,” we have not seen it till we observed Dr. Woodward’s notice of the 
circumstance in the “Lens.” This is because the “ Quekett Club Journal” 
* “ Monthly Microscopical Journal,” vol. iii. p. 16. 
