General Science. 
m 
physical relations of mineral bodies, and embracing an account 
of those remarkable phenomena which have been detected in 
crystallized substances by the agency of common and polarised 
light. In this work* the unerring characters which are derived 
from optical structure will be substituted in place of the ambi- 
guous distinctions which have been generally employed ; and the 
student will be allured to a knowledge of the science, when he 
finds that, in addition to the usual qualities of weight, lustre, 
and external form, minerals possess an internal organization which 
displays itself by the most beautiful optical phenomena, and 
exercise functions of a physical nature not less interesting than 
those which are exhibited in the agencies of animal and vege- 
table life. This Treatise will consist of two volumes 8vo., with 
numerous plates, and will be preceded by an Introduction, con- 
taining a popular account of the action of crystals upon polar- 
ised light ; an explanation of the new method of determining 
primitive forms from the number of axes of double refraction ; 
and a description of various new methods and instruments for 
examining and distinguishing the precious stones and other mi- 
neral substances. In his mineralogical investigations, the author 
has had the advantage of the freest access to the cabinets of Mr 
Thomas Allan and Sir George Mackenzie, and has been sup- 
plied in the most liberal manner with individual minerals from 
the cabinets of Mr Ferguson of Raith, Mr Heuland and Mr 
Brooke. He will still, however, receive with gratitude, and 
carefully return, any curious specimens of rare minerals which 
may be entrusted to him for examination. 
34). Method of playing on the Violin and Violincello at the 
same time. — In Vol. iii. p. 194. of this Journal, we mentioned 
the ingenious contrivance for this purpose, by Mr James Wat- 
son, a blind musician from Dundee. Since that time he has 
not only improved but extended the mechanism, and we had 
the pleasure of seeing it exhibited before the Directors of the 
Asylum for the Blind, to the satisfaction of all who were 
present. The following account of the improved mechanism 
is taken from No. 8. of the Caledonian Quarterly Journal : 
u The stops by which he shortens the strings of his violincello 
have been fitted with more elegance and precision, additional 
springs have been added, to assist and relieve his leg in the ope- 
