21 
II. — A New Erecting Camera Lucida. 
By Edward M. Nelson, F.K.M.S. 
{Read 21 st November , 1894 .) 
Some few years ago we had an eruption of cameras, when every con- 
ceivable kind of prism was cut and tried, it would therefore under 
these circumstances seem impossible to bring forward any new form. 
If, however, we bear in mind that nearly all new ideas and inventions 
are complex, and subsequent improvements simplifications ; and if we 
glance back at the multitude of complicated prisms which have long 
since passed away, we may find ample room for simplification. 
Probably the most persistent of all forms of cameras ever de- 
signed is that known as Beale’s neutral tint. It is acknowledged on 
all hands to he a defective form, but solely on account of its simplicity 
it is still largely used. There is only one defect in Beale’s camera, but 
that is a serious one : the microscopic image as received at the eye- 
piece is inverted and transposed ; now Beale’s camera corrects the 
inversion, while it leaves the transposition untouched, therefore all 
objects drawn with this camera are unlike the originals. A drawing 
made with this camera will only be similar to the original when it is 
drawn on tracing paper and viewed from the wrong side. 
This point is so important, and I fear so imperfectly understood 
by microscopists as a body, that a very simple example may be 
pardoned.- Place the letter F on the stage in the position as here 
printed : when examined by the Microscope it will appear thus d . Now 
in order to view this letter as the original all that we have to do is 
to turn this paper round. But this object as drawn by a Beale’s 
camera will appear d, and, turn the paper which way you will, it can 
never become like the original; it will only become so when it is 
viewed as a transparency from the other side of the paper. 
For micrometry and brass and glass work, this transposition is not 
of much moment, but in biological work it is of the utmost importance 
that things should be depicted as they really are. Thus there are 
some insects which have the right leg longer than the left ; in drawing 
these therefore it would he making a serious error to reverse the 
order. 
The difficulty with regard to the erection of the image has in the 
main been overcome by reflecting the image of the paper and pencil 
down the tube of the Microscope. The drawing thus made will of 
course be inverted and transposed, but by turning the picture round 
we at once have a correct representation of the object itself. 
The instrument for this purpose which in recent years has come 
into considerable notoriety is that known as Abbe’s camera lucida. 
