SCIENTIFIC SEMMAEY. 
131 
An Improved Solar Camera. — Towards the end of August last, a singularly 
perfect collection of enlarged photographs were exhibited at the establish- 
ment of Mr. Thomas Eoss, the optician. These were shown in illustration of 
a new dialytic enlarging apparatus, invented by M. D. Monckhoven, a name 
long and favourably known to the scientific portion of the photographic 
world, although that of a very young man. It is based upon the principle 
of Woodward’s American solar-camera, but the field of iUumination obtained 
is more equal, the possibility of distortion is avoided, and it works with a 
greater degree of ease and certainty. Its chief exterior features consist in an 
improved mode of working the external refiector, and in the curves of the 
condenser, being so calculated as to reduce its spherical aberration to a mi- 
nimum. But the most original and valuable improvement is in the introduc- 
tion of a new lens, in the form of a divergent meniscus, placed at a distance 
equal to that of its diameter from the condenser, and made very thin i^ order 
that as little light as possible may be lost by absorption. This lens acts by 
bringing the central and marginal pencils of light to one plane (represented 
by the negative as placed within the camera), and also by bringing into its 
focus a larger body of light than was obtainable by the older process. The 
object-glasses, used to transmit the image, also have certain peculiarities for 
cutting ofi“ diffused light, &c. The specimens produced by this apparatus 
speak highly for its capabilities ; but we are sorry to hear that it is likely to 
be very expensive. 
The New Magnesium Light — Dr. E. L. Maddox has recently detailed his 
mode of using this new light as applied to photo-micography. He says of 
the light : — “ It was very late in the evening before I had time to try it with 
my usual helio-camera apparatus. Having removed the prism, I placed a 
small paraffine lamp so as to illummate the object, condensing the rays by 
the small crossed condenser of Smith, Beck, & Beck’s microscope. After 
obtaining a careful focus on the screen with the two-thirds objective, the 
exact distance of the centre of the flame from the condenser and the base 
board was noted. The two-thirds objective used was corrected by a back 
lens for union of the actinic and visual foci. A small lighted spirit lamp 
was then arranged to replace the paraffine lamp. The image on the screen was 
now scarcely visible. A prepared wet collodion plate was put iuto the frame, 
the piece of wire held in one end in a pair of pliers, the shutter opened, the 
shade between the condenser and object removed, and the wire instantly 
placed somewhat obliquely, for one-fifth of its length, in the flame of the spirit 
lamp. It soon ignited, emitting a brilliant light, and was advanced as 
equally as the hand could regulate, according to the rate of consumption. It 
gave out many scintillations, and on reaching the point of the iron nippers, 
; finished by a smart explosion (possibly the ends of the pliers were damp). 
The wire (1-^ inch) lasted but a few seconds. Portions of the wire (three- 
; eighths to half an inch) were left unbumt.” The resulting photograph (the 
I leaf insect of the sycamore) when contrasted with one of the same minute 
j object taken in sunlight, is very deficient in sharpness and definition. This 
difference between photographs taken by artificial light and by sunlight 
j always seems to exist, and many theories have been advanced to account for 
! the fact. The editor of the British Journal of Photography suggested to 
j Dr. Maddox that the actinic and visual foci of the objective might be differ- 
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