Miscellaneous Intelligence. 291 
the same focal lengths and aperture. It is obvious that by such meth- 
ods only fortuitous results could be obtained, no data existing by which 
new combinations could be calculated without vast labor, and the artist 
himself entertaining no hope that. his materials were capable of yielding 
higher results, ; 
The reason of this conclusion may be briefly stated. At an early 
stage of the improvements of the achromatic microscope, it was assume 
as essential, that the different combinations should be so calculated as to 
permit the inner surfaces of the crown and flint lenses to be cemented, 
he app is essay 5 
yond which the artist had no expectation of success. 
So late as the’ year 1844, Mr. Ross, then, as now, the first of Euro- 
Pean artists, in announcing that, with his 7yth objective, he had reached 
the angle of aperature of 135°, declared, that a pencil of that angle, 
es ‘the largest that could be passed through a microscope object- 
glass.” 
It was under such circumstances of embarrassment, or rather of ap- 
parent hopelessness, that I continued the series of investigations, before 
began, which had for its object the improvement of the microscopi¢ 
Meee glass, in the very particular which was declared impossible by 
t. Ross. 
ctives. veshnin: ; 
Many new, unexpected, and sre results ware Loupineds in pd 
ence to both the optical and physical characters. | interesting ™ 
terial. . During the long course of labor and study, which these inves- 
