1864. ( 20 
NOTES AND CORRESPONDENCE. 
On the Highest Magnifying Power of 
the Microscope yet employed. 
In giving a very brief summary of 
my recent observations upon the 
mode of termination of the nerves 
in voluntary muscle, the editor of 
‘Cosmos,’ for August 28th, 1863, 
remarks :—‘‘ Nous regrettons pour 
notre compte que M. Beale n’ait 
pas dit dans sa note avec quel genre 
d’oculaires et avec quel jeu de len- 
tilles il a pu obtenir le prodigieux 
grossissement de 3,000 fois.” 
I propose in the present short 
communication to describe briefly 
how my drawings representing ob- 
jects magnified to this extent were 
obtained. In making drawings of 
microscopical objects, it is usual to 
represent the image the size it 
appears when thrown upon paper 
with the aid of the camera or 
neutral tint glass reflector at the 
distance of 10 inches from the eye, 
the arbitrary point at which the 
magnifying power of object-glasses 
is measured. If the image be taken 
at a point nearer to the eye it ap- 
pears smaller; while, at a greater 
distance, it of course appears much 
larger than at the arbitrary distance 
above stated. Large diagrams may 
indeed be made direct from the 
microscope, by placing the diagram 
paper at the distance of 3 feet or 
more from the eye, and tracing 
upon it with a long pencil the ob- 
ject as reflected from the neutral 
tint glass reflector. 
In practice, I have often found 
it almost impossible to represent, 
in drawings, lines as fine as those 
seen in the preparation. A certain 
coarseness is inevitable. The copied 
lines and markings appear rougher 
and thicker than the real ones. 
But this defect is to some extent 
removed by drawing the™® object 
somewhat larger than it appears to 
be magnified at the distance of 10 
inches from the eye; and, in order 
to obtain uniform results, I always 
draw the object the size it would 
appear if copied on the same level 
as the stage of the microscope. 
The scale for measurement is copied 
at precisely the same distance. A 
glass which at 10 inches is said to 
magnify 200 diameters will magnify 
215, and my high power, which was 
made for me two years since by 
Messrs. Powell and Lealand, instead 
of magnifying about 1,600 dia- 
meters, increases the image of the 
object to 1,800 diameters. By in- 
creasing the length of the tube of 
the microscope between 4 and 5 
inches, I obtain an amplification 
amounting to 3,000 diameters, and 
the y¢55 of an English inch becomes 
3 inches in length. 
With care in illumination, I have 
been able to see points in an object 
magnified with this power which I 
had failed to observe under a power 
of 2,000. It seems to me probable 
that I may succeed in increasing 
the power to 5,000 diameters ; and 
with this object I am trying different 
plans, the results of which shall be 
recorded shortly. The common 
paraffin lamp gives a very white and 
good light for working with these 
high magnifying powers. I have 
tried the lime light, but have as yet 
reaped no advantages from its use. 
So far I have certainly obtained 
better results by increasing the 
length of the tube of the microscope 
