The Columbian Exposition. — Williams, 347 
illustrated, as they were thrown from one position into an- 
other, the relations of a form in one crystal system to the 
corresponding form in any other. 
In the central west gallery of the Mining building. Dr. F. 
Krantz of Bonn had displayed a large assortment of his un- 
rivalled crystal models, now too well known to require special 
mention. These are of glass and of two different sizes in 
wood, and for stability, accuracy and cheapness are unsur- 
passed. 
Other less important exhibits of crystal models were made 
by Apel of Gottingen in the German University gallery of 
the Department of Liberal Arts, by the Russian pedagogical 
museum, and by Ward of Rochester. 
Very important optical instruments relative to mineralogy 
were to be seen in the German University exhibit in Liberal 
Arts; in the German Association of mechanical and optical 
manufactures in the N. E. gallery of the Electrical building, 
and in the French educational exhibit. Here the well-known 
instruments of Fuess,Voigt and Hochgesang, Steegand Renter. 
Zeiss, Apel, Nachet and Werlein, were displayed and full de- 
scriptive catalogues given to all persons interested enough to 
ask for them. Most of this apparatus is already familiar to 
mineralogists, although there were not a few novelties, espe- 
cially in the wa} T of refractometers, goniometers, and micro- 
photographic appliances. 
Various pieces of optical apparatus for mineralogical pur- 
poses were also exhibited by others than manufacturers, as 
for instance, Mr. G. F. Kunz in the Mining building gallery, 
Harvard, Columbia, Johns Hopkins, and other universities in 
the Liberal Arts. 
Microscopes especially designed for mineralogical and pet- 
rographical investigations were displayed in various widely 
separated exhibits. Those noticed and examined by the writer 
were by Fuess of Berlin (German University gallery), by Sei- 
bert of Munich (Krantz exhibit), by Voigt and Hochgesang of 
Gottingen (Electrical gallery), by Zeiss of Jena (same), by Leitz 
of Wetzlar (with Richards & Co., .Mining gallery), by Nachel 
of Paris (French gallery), and Kunz ( in Mining building), and 
by Bausch and Lomb of Rochester. English instruments by 
Swift and Beck were also in the English educational gallery. 
