Physics and Chemistry. 215 
most favorable arrangement for use with high powers (and 
_ equally with low) would call for, and the standard length of 
microscope body admit of. But the aperture of the lenses might 
_ Temain about the same. 
aving obtained by this means a pencil (or beam rather) 
transmitted through the eye-piece of the greatest possible di- 
mension or area, at the point of binocular division, greater 
amplification in the eye-piece, as to its total power, might be ad- 
_ Vantageously effected by means of lenticular immergent and 
_ emergent surfaces of the upper prisms; the lower face of each 
prism to be convex, the upper emergent surfaces concave, giving 
achromatized refraction in each case. By this means, a larger 
field, together with a minimum length of tubes above the prisms, 
would be secured. 
By thus appropriating every surface of all the prisms not a 
_ Teflecting surface, for the purpose of lenticular refraction, the 
Se), ap pO a eae ee eS 
ens of the eye-piece can be dispensed with, Its utility, as thus 
plied to those telescopes too large to be conveniently in the 
ouble form, is too obvious and striking to need remark. The 
view thus obtained is truly stereoscopic. 
Canastota, N. Y., Dec. 1864. 
SCIENTIFIC INTELLIGENCE. 
I. PHYSICS AND CHEMISTRY. 
perth spectra, the i. being themselves more numerous and distinet 
Sei in the spectrum produced by a flint glass prism. | The observations 
— calculated according to the well known formula 
esind= mA, 
‘ 
. 
