50 REPORT—1863, 
ieries of this district, where it occurs and is associated with coal, and is known by 
the name of coal brasses. But since 1856 other and more abundant supplies have 
been obtained from Spain, Portugal, Belgium, Westphalia, Norway, Sweden, and 
Tuscany. At present the total consumption of pyrites on the Tyne and neighhbour- 
hood is about 70,000 tons per annum, representing a value of about £105,000. The 
preceding Table represents the composition of the principal kinds of pyrites at 
resent used, The samples analyzed are chiefly fair average samples of cargoes 
fugit to the Tyne. 
No. 1. Spanish pyrites, obtained from the districts of Huelya in Spain and 
Algarve in Portugal. About 30,000 tons per annum used on the Tyne. No. 2. 
Ditto. No.8. One of the Belgian varieties, obtained from the Rocheux mine, 
Theux, near Spa. About 12,000 tons of Belgian pyrites used on the Tyne per 
annum, No. 4. Westphalian pyrites. Consumption on the Tyne about 8000 tons 
per annum, This is one of the most abundant sources of the newly-discovered 
metal thallium. No. 5. Norwegian pyrites, obtained from the island of Ytterden, 
in the Bay of Drontheim. About 6000 tons per annum used on the Tyne. No.6. A 
rich variety of Irish pyrites, obtained from the Wicklow mines. About 4000 tons 
of Irish pyrites used on the Tyne per annum. No.7. Coal brasses, sample obtained 
from the Walker Colliery. About 7000 tons per annum used on the Tyne for the 
manufacture of sulphuric acid. Other analyses of pyrites were also given in the 
paper. The process adopted by the author in estimating the amount of sulphur, 
the methods of burning, the treatment of the residuum, and various objectionable 
varieties of pyrites were also described. 
On a New Method of Measuring the Chemical Action of the Sun’s Rays. 
By Dr. T, L. Purpson. 
The author happened to notice that a solution of sulphate of molybdic acid 
(that is, a solution of molybdic acid in excess of sulphuric acid) standing in his 
laboratory upon a shelf which is ed exposed to the sun for about three hours 
each day became bluish green in the daytime and colourless again at night. 
In sunlight...... Mo0?+ HO=Mo0?+ HO? 
At night,....... Mo0?+HO?=Mo0'*+ HO. 
This change is produced by the chemical action of the sun’s rays: heat will not 
effect it; for the solution boiled did not change colour. 
Nothing is easier than to measure with the greatest accuracy the amount of 
reduction which takes place *by the sun’s action in a given time. The actinometric 
liquid is prepared by dissolving molybdate of ammonia in excess of sulphuric acid, 
introducing metallic zine until the liquid becomes dark blue, and then adding a 
solution of permanganate of potash until the last drop restores the liquid to its 
primitive colourless state. A provision of the liquid haying been made, twent 
cubic centimetres are exposed to the direct rays of the sun for one hour (11 to 19) 
each day. It is then withdrawn, and the amount of reduction measured by a 
standard weak solution of permanganate of potash. This is delivered from a 
pipette with bulb and long thin stem, graduated into 100 equal divisions. After 
each insolation, the degree read off the pipette gives for each day the relative 
amount of actinism, just as a thermometer gives the degrees of heat. 
From a short series of experiments, it appears that the variation of the chemical 
action of the sun’s rays describes curves which are not only irregular, but present 
sometimes sudden deflections, calling to mind barometric curves, to which they may 
perhaps be related. 
On Musical Sounds produced by Carbon. By Dr. T. L. Purpson, 
When a rod of glass is suspended by a string, and struck with a hammer, it 
emits a beautiful musical sound—a fact turned to account in the instrument called 
the Harmonica, The same happens with phonolite, certain varieties of flint, and a 
few other minerals. In quarrying mountain-limestone, wedges are driven into 
holes drilled in the rock in order to break it; and the author noticed once, in 
Belgium, that the instant a slab separates in this manner, a peculiar musical sound 
shoots through it. Among the elements, none are perhaps more remarkable in 
