118 Tue Microscope. 
Dr. Schott’s disposal, united with them, and in the beginning of 
1884 glass-works were set up, with a large furnace and machin- 
ery. The Prussian Government’s subsidy was 3,000 /., and given 
under conditions as liberal as any Government has ever granted 
when putting public money into the hands of private persons. 
The new furnace was lighted in September 1884, and since 
that time Dr. Schott has been actively engaged, almost day and 
night, in overcoming the difficulties of the operations. The 
experiences of other manufacturers being inaccessible to a new 
competitor, everything had to be learned anew. A year later, 
the first part of the matter was brought to an end—the produc- 
tion of the ordinary siliceous glass, and this, since last autumn, | 
is used by nearly all German opticians. In afew months, it is 
hoped, that the borates and the phosphates will also admit of 
regular production, and then the Jena manufactory will be 
opened for the supply of optical glass on a strictly scientific 
basis. 
This extension of the work has had the effect of delaying 
the introduction of better glass into microscopical optics by 
more than two years. In the summer of 1883, sufficient mater- 
ials had been obtained for the construction of microscope-lenses, 
and, in fact, the first objectives were made by Messrs. Zeiss at 
that period, but after it had been decided to-establish a manu- 
factory with the aid of public money, Messrs. Zeiss were obliged - 
to abstain from using the new glass, and to wait until the latter 
should be accessible to other opticians also. 
At present the objectives are not on sale, but it is expected 
that very shortly both objectives and glass can be purchased in 
the usual way. . 
Mr. E. M. Nelson, who has had our objective under exam- 
ination, writes as follows :— 
“The great benefit which will accrue to microscopists from 
the use of lenses of this construction will be due, not so much 
to the absence of color as to the great freedom from spherical 
aberration. In other words, these lenses will stand illuminating 
by axial cones of larger angle. This is evident trom the pér- 
formance on Vavicula rhomboides (Cherryfield). This diatom, 
which under oblique light is a test for a 4 of 90°, becomes a 
pretty severe test for the widest-angled homogeneous-immersion 
