Miscellaneous Intelligence. 447 
in some cases radii of less than one-tenth of the focal length. Each lens is 
a meniscus, whereas the oe has lesen been to make both the sur- 
faces of the crown lens ¢ 
vex, see more or Jess vari- 
ation in the proportion of 
So—>S- | SEDdvLLdcdrlCsS Ome 
in comparison with the 
Fraunhofer lens, 
their confidence to so deci- 
ed a departure from established usage, oneeiells as there may have been 
reason for ap ee ee Seta difficulties in working surfaces to cor- . 
respond with the new curves, Yet these = have certainly now 
en overcome, at least ‘on lenses of moder Bp a and it is un- 
derstood that the Messrs. Steinheil are capers a apply the system to 
ose of the largest size for which suitable material can be pro- 
cur 
The chief advantage proposed to be gained is the more complete 
sora! of the indistinctness caused by the pa ia of the rays of 
different colors, without sensibly increasing the influence of spherical 
aberration even when the ratio of the aperture to the les ngth is con- 
siderably increased above its usual proportion. In the opinion of com- 
eg judges, Los trials which have thus far been made of gry of 
are in we Siteungsberih der k. bayer Akad, der Wiss. gota 1860, 
Heft. i 4 
Boox 
a 
1. Storer’s Dictionary of the Solubilities o Chemical Substances, 
Part Il, pp. 233-456.—This part th ect down to 
ng. 
2. Practical Treatise on Limes, . Hydraulic Cements and Mortars, 
containing reports of numerous experiments 2 geome in New York City city, 
1858 to 1861; by Quincy A. Gimore, A.M, . General U.S 
and Major U. S. Corps of Engineers. ‘Nes York: D. Van Now 
