Rainey on Artificial Light. 
23 
A Method of employing Artificial Light for the Illumina- 
tion of Transparent Objects, by which it is so depinved of 
Glare and Colour as to he equal in its Illuminating Power to 
the best Daylight. By Geo. Rainey, M.R.C.S., Demon- 
strator of Anatomy at St. Thomas's Hospital. (Read June 
22, 1853.) 
The principal disadvantages attending the use of gas and 
lamp light, as they are ordinarily employed for microscopic 
illumination, are the disagreeable and somewhat painful glare 
and the unnatural colour which is given to all objects thus 
illuminated. 
These inconveniences are not felt so much where only a 
plane or concave mirror is used, as when the light is concen- 
trated upon the object by an achromatic condenser ; and, in 
the former case, they are partially remedied by transmitting 
the light through a piece of ground glass, either common or 
coloured ; or by dulling the surface of the mirror ; but in the 
latter one, these means, by cutting off too much light, are 
productive of more harm than benefit, especially where the 
markings upon an object are very delicate and require a parti- 
cular kind of illumination to render them distinctly visible, 
as, for instance, the dots on the Pleurosigma angulatum. 
Hence, unless some other plan be adopted for moderating the 
intensity of all artificial light and correcting its colour, the 
employment of the achromatic condenser must either be 
limited to the hours of a good daylight, or the observer be in 
danger of materially injuring his eyesight. 
Mr. Gillett's apparatus for producing the effect of a white 
cloud does, I am informed, remedy all the defects of lamp- 
light, but, from some difficulty or other in constructing or in 
applying it, its employment has not become general. 
The plan to which I have to call your attention is especially 
applicable to Mr. Gillett's condenser, and may at a compa- 
ratively small expense be made a part of that most useful 
instrument. 
Before proceeding further I may observe that the principle 
upon which my apparatus is constructed is one which has 
been of general adoption for the preservation of the eyes of 
those who use glasses, and therefore so far has no claim to 
originality ; but its precise construction and application to the 
microscope, and its effect in rendering artificial light equal if 
not superior to the very best daylight, are admitted by those 
who have seen it, and, to the best of my knowledge, are also 
new. But my motive has not been novelty but utility, in 
bringing this subject under the notice of this Society. 
