142 
Progress in Science. 
January, 
all composed of nltro-glvcerine, viz., dynamite rendrock and vulcan-powder 
in separate cartridges or canisters. Fifty thousand pounds of these explosives 
were buried in the apertures. Ninety-six galvanic batteries, of ten cells each, 
were employed to ignite the charges. The firing point was 650 yards from the 
shaft, and the amount of leading and connecting wire used to bring all the 
charges into relation with the batteries was 220,000 feet. The charges in the 
different holes of the same pier were connected so as to explode simultaneously, 
but a fuse composed of a quick explosive was used to connect the system of 
charges in each pier with those of the neighbouring piers. In this way the 
electric spark taking effect in a few centres, the ignition was propagated 
through the whole system, as the explosion of the connecting fuse would 
advance more rapidly than the destruction of the rock. The several thousand 
charges in the mine were connected in 23 groups of batteries. These were 
ingeniously connected in a mechanical arrangement so simple and perfect that 
a child could operate it, and the whole stupendous force that slumbered in the 
charges was actually released by the touch of a little daughter of General 
Newton, two years and a half old. The explosion was accompanied by no 
very stunning effects to eye or ear, and the demonstration was so moderate as to 
produce great disappointment in the crowds who assembled to witness it. 
There was a succession of shocks, lasting a few seconds, with no great noise, 
a mass of water and debris of the coffer-dam thrown into the air, and the 
great reef was shattered and demolished. 
TECHNOLOGY. 
At the meeting of the Chemical Society on November 2nd, a preliminary 
notice by Messrs. W. R. Hodgkinson and H. C. Sorby was read, on “ Pig- 
mentum nigrum, the Black Colouring-matter contained in Hair and Feathers.” 
"When perfectly white hair or feathers are heated gently with dilute sulphuric 
acid for some time they completely dissolve, but if black or brown feathers or 
hair are thus treated an amorphous black residue is obtained. This substance, 
which exists only in very small quantity in the blackest feathers, may be con- 
veniently prepared from rooks' feathers (which yield about one per cent) which 
have been separated from the central rib, and thoroughly cleaned from waxy 
and fatt}’ matter by treatment with alcoholic ammonia. On digesting them 
with successive quantities of dilute sulphuric acid for several days, until the 
acid ceases to be coloured by red or brown soluble colouring-matters, a black 
residue is obtained, which, after being thoroughly washed with dilute hydro- 
chloric acid at So 3 C., and then with water, is dried, and the last trace of fatty 
matter finally removed by treatment with boiling alcohol and ether. On 
analysis it gives numbers agreeing very well with the formula CGsHigNaOs. 
It is not acted on by dilute acids or alkalies, but nitric acid slowly oxidises it. 
It forms new compounds by the action of bromine, one of which is soluble in 
water, and gives a characteristic absorption spectrum. 
At the Chemical Works at Aalborg, in Jutland, Denmark, where about 
30 tons of alkali are made per week by the ammonia process for obtaining 
alkali from seaweed, Mr. Thowald Schmidt, the Director of the Manufactory, 
proposes to work, in conjunction with this process, a method devised by him- 
self of treating seaweed so as to obtain iodine, potash salts, and other market- 
able products therefrom. In Denmark a very heavy duty is levied on the 
importation of common salt, whilst enormous quantities of seaweed rich in 
iodine and potash can he obtained at small cost in the neighbourhood of the 
works. Mr. Schmidt’s process is as follows : — After the seaweed is dried and 
burnt a concentrated solution of the ash is made and added to the liquor con- 
taining chlorides of sodium and calcium, left after the ammonia has been 
recovered in the ammonia-soda process by boiling with lime. The sulphates 
of potash, soda, and magnesia contained in the ash of the seaweed are thereby 
decomposed, and hydrated sulphate of lime and hydrated magnesia are preci- 
pitated in a form which may be available for paper-making as 11 pearl-hardening.” 
The last traces of sulphates are got rid of by adding a small quantity of solu- 
tion of chloride of barium. To the clear solution nitrate of lead is now added 
