SCIENTIFIC SUMMARY. 
327 
The Metallurgy of Lead. — Mr. John Jex Long read the first part of a 
paper on this subject before the Glasgow Philosophical Society, March 25, 
1872, in the course of which he described the operations which he had 
personally witnessed at the works of the London Lead Mining Company, at 
Middleton-in-Teesaale, a few miles from Barnard Castle, where the mining 
operations were commenced about 170 years ago. He explained the geolo- 
gical position of the lead-bearing rocks in Teesdale, describing the direc- 
tion, extent, and richness of the mines, and their mode of occurrence in flats, 
pockets, strings, &c. The annual product of the mines referred to is about 
2,000 tons of metallic lead, containing about 9 ozs. of silver per ton, which 
is separated in the metallic form by Pattinson’s process. Before the com- 
pany obtained any pecuniary return from the mines, they had to expend 
about 30,0007 Mr. Long described his exploration of the Coldberry Mine 
at Middleton, the mode of working it, and the various mechanical operations 
by which the mineral is prepared for smelting ; and he promised, on a sub- 
sequent occasion, to devote the second part of his paper to the considera- 
tion of the smelting and refining processes and the extraction of the silver. 
The paper was profusely illustrated by specimens. 
Waste of Sulphur in Mining. — Dr. W. H. Tayler writes to the 11 Chemical 
News/’ May 24, upon this subject. He states that whilst minerals of every 
description are rising in value, it will scarcely be credited, although such is 
the fact, that in several of the tin mines in Cornwall, at the present time, a 
large source of what ought to produce wealth is allowed to be wasted. 
Large quantities of sulphurous fumes are allowed to pass off daily in calcin- 
ing the tin stuff, instead of manufacturing it into sulphuric acid. He states 
that he knows of an instance where three tons of sulphur are daily allowed 
to escape, which if manufactured into sulphuric acid, the present price of 
which is SI. 10s. per ton, would yield a revenue of more than 12,0007 a 
year. While Spain and Portugal and other parts of Europe are ransacked 
to find sulphur ores to supply the manufacturers of sulphuric acid, in Corn- 
wall all these sources of wealth are allowed to be wasted. 
Crystalline Dissociation. — MM. Favre and Valson have published the second 
part of a very valuable monograph on this subject. It contains so large a 
series of tabulated forms, the results of experiments, that an abstract would 
be impossible. 
MICROSCOPY. 
Wenham's improved Itejlex Illuminator for the highest powers of the 
Microscope. — We cannot resist giving our space to this excellent invention 
of Mr. W enham’s for microscopic illumination. The diagram (p. 329), five 
times the size of the instrument, illustrates the plan he has adopted to over- 
come the defects of the olden apparatus. In this a is a cylinder of glass 
half an inch long and four-tenths in diameter, the lower convex surface of 
which is polished to a radius of four-tenths. The top is flat and polished. 
Starting from the bottom edge, the cylinder is worked off to a polished face 
at an angle of 64° : close beneath the cylinder is set a plano-convex lens of 
1£ focus. Parallel rays sent through the lens, after leaving the lower 
convex surface of the cylinder, would be refracted to the point shown by the 
