( 370 ) 
[June, 
NOTES. 
The notices in the various newspapers of the “Giant Electric 
Microscope” at the Crystal Palace are amusing. All of them 
seem charmed with the enormous magnifying power of the in- 
strument : that the eye of a small sewing needle can be enlarged 
to the apparent dimensions of 6 feet by 4 is evidently to these 
critics a performance surpassing that of any microscope yet con- 
structed, and doubtless wonderful enough to those unfamiliar 
with the performance of the instruments commonly used by 
microscopists. Magnifying power alone has long ceased to be 
the great desideratum with workers ; if everything else is sacri- 
ficed there is very little limit in this direction, provided light can 
be found to render the enlarged image brilliant enough to be 
seen. Definition is quite another thing : this taxes the skill of 
the optician to the utmost, and demands the most exaCt correc- 
tion of the aberrations ; great perfection has been reached, and 
the modern microscope has already accomplished that which 
theory formerly declared to be impossible. With regard to 
images thrown upon a screen very good definition is attainable ; 
when a large surface is not required to be covered the fine 
quality of the numerous representations of microscopic objects 
by photography affords ample proof of what has been done, — all 
that the best microscopes can render visible has under certain 
conditions been faithfully reproduced. The delineations of 
the supposed minute markings on inseCt scales and diatom valves 
are marvellous, surpassing anything that the human hand can 
depicft. Unfortunately, however, when the amplification is in- 
creased to an amount sufficient to render minute objects visible 
to a large audience, definition breaks down altogether, and only 
an enlarged image, of which the minute details are badly or not 
at all rendered, remains. The late Andrew Ross endeavoured 
to improve the definition of the projection microscope, but ob- 
tained no very good result. At present the only way of exhibiting 
a microscopic objeCt on a screen in a satisfactory manner is to 
enlarge a photo-micrograph by means of a good magic-lantern ; 
admirable results are obtained by this indirect method, while the 
direct projection of the magnified image of a minute objeCt is at 
the present time a desideratum. The “ Giant,” so far as inves- 
tigation is concerned, can be surpassed by a pigmy in the shape 
of a good pocket lens. 
M. E. L. Trouvelot considers that the rings of Saturn cannot, 
on account of their changes of form, be regarded as solid bodies. 
