320 THE NORTHERN MICROSCOPIST. 
wide aperture; by describing the effect produced with a slide of Polycistina placed under 
a half inch objective of S00. 
“‘ The result was a glare ;—no definition, no penetration.” Mr. Stanley's inexperience leads 
him astray somewhat, and he innocently mixes up cause and effect. More of this however 
anon, and in another place. 
I have a)so carefully noted the remarks of *‘ Photo,” “‘ Micro,” and ‘One who was pre- 
sent,” but must respectfully decline to notice “ Anonymous” correspondents, and should 
prefer those of my opponents who are members of the Manchester Microscopical Society to 
show themselves openly and manfully, an opportunity presenting itself at the Society's 
next meeting, when two or more papers will be read on the Aperture question,—Yours 
respectfully, J, L. W. MILES, 
On receiving the above letter for insertion, we returned it to the writer for revision as we 
thought that upon mature consideration he would not desire to weaken his case, by 
charging with inexperience, one who is already known to our readers by his articles on 
Mosses, The letter came back to us unrevised, with a few personal remarks, which we do 
not reproduce, and a second request for publication. In acceding to this request we wish 
to inform our readers that Mr. Stanley's experience may be judged from the fact that the 
whole of the drawings illustrating his articles were drawn by him from the microscope, we 
reproducing them in facsimile by photo-zincography. Mr, Jennings, we hope, will only 
smile at his facts being written oyinions,—(Eb,} 
NOTES AND QUERIES. 
CHANGE oF AppREss.—The Editor desires to call the attention 
of his correspondents to his change of address. It is now 
The Willows, Fallowfield, Manchester, where all communications 
should be addressed. 
Microscopic Stupy or Dyep SiiKs.—The Chemical Review 
recently contained an interesting notice on the appearance of dyed 
silks under the Microscope. There is a striking difference between 
the fibre viewed lengthwise and in cross-section. In the former 
case the dye appears uniform, but in the latter it is seen that the 
colouring matter lies in circles round the centre of the section, its 
intensity usually increasing from the centre to the circumference. 
If specimens of silk be taken at intervals from immersion in dye- 
liquor, the breadth of these coloured rings will be seen to increase 
till they reach the centre. When silk, already dyed a light shade, 
is dyed to saturation with a second colour, the section will exhibit 
an inner circle of the pure second colour and an outer ring in 
which the two colours are blended. _ If, however, the silk is dyed 
to saturation the first time, and but lightly the second, the inner 
circle will be of the original colour, while the outer ring exhibits 
the result of the two. 
Heat has sometimes a great effect in promoting the penetrating 
power of the dye. Thus, Prussian blue gives a broader ring in 
two hours aided by heat than in twenty-five hours in the cold. In 
five hours when heated, the tint is uniform throughout. If, how- 
ever, a silk be ironed and blued imperfectly, and afterwards dyed 

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