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LV. Intelligence and Miscellaneous Articles. 
ON A NEW STEREOSCOPIC PHENOMENON. BY M. A. CIMA. 
| TAKE a drawing of a head seen in front, of 3 or 4 centimetres in 
height; it may be lithographed, or engraved, or drawn with a 
pencil. I cut this drawing in the direction of the vertical axis of the 
nose, and arrange these two parts of the drawing in the same vertical 
plane, before the eyes, at a less distance than that of distinct vision. 
I remove or bring together the two parts of the drawing until the 
two images which result from their duplication, combine so as to 
form the entire face. The image of this face thus obtained pre- 
sents the appearance of a solid object, or of a modelled figure in 
which the nose, the cheek-bones, the chin, and the eyebrows are 
detached, as in an object in relief. This sensation of relief in- 
creases in proportion to the length of time during which the two 
images are viewed; to obtain the maximum of effect, the two half- 
faces must be held at a suitable distance, which varies according to 
the observer. A similar, but much less perfect effect is obtained by 
looking at the drawing of the entire face, either with one or both eyes, 
at a distance much less than that of distinct vision. 
I think that the explanation of these phenomena must be founded 
upon the two following facts, which led me to make the observation 
which is the subject of this note. The eye sees of a gray colour a 
series of very small alternate black and white spaces, very close to 
each other, and seen at a distance less than that of distinct vision. 
In looking at a single face divided into small squares alternately 
black and white, at a distance less than that of distinct vision, the 
white squares appear larger, the lines of contact between the white 
and black squares become of a gray colour, which extends gradually, 
and the black squares appear larger; at the same time the white 
squares appear to be raised at the centre and the black squares to be 
hollowed. This double property of our eye, which is due to 
ocular irradiation, furnishes us with a sufficient explanation of this 
new stereoscopic appearance.—Comptes Rendus, October 26, 1857, 
p. 664. 
NOTE ON M. RUHMKORFYF’S INDUCTION COIL. 
To the Editors of the Philosophical Magazine and Journal. 
GENTLEMEN, Boston, Mass., Oct. 20, 1857. 
I notice, in the September Number of your Magazine, my paper 
from Silliman’s Journal, giving a description of my construction of 
the Ruhmkorff induction coil. I have since (in July last) con- 
structed one with 60,000 feet of wire on the same principle, which 
gives sparks of 103 inches in the atmosphere with two cells, Bunsen’s 
battery. This instrument is in the possession of Columbia College, 
New York. 
Respectfully yours, 
E. 8, Rrrontre, 
