163 
but in an instant I was thrown forwards — then came a vio- 
lent tremor — and lastly a settling back into my original posi- 
tion. The duration of the shock was not more than four or 
five seconds. On making inquiry I found that many others 
had experienced similar sensations, and that much alarm 
had been created by the shock. In some of the mills the 
looms appeared to be heaved up — doors were displaced — 
and the more delicate machinery thrown out of gear. House 
bells were set ringing, and the crockery rattled as if about 
to fall from the cupboards. The dogs howled as if in 
alarm — the canary-birds fluttered about in their cages — and 
several horses refused to move on for some time after the 
shock. In the higher parts of the town the walls of the 
houses swayed to and fro, and now exhibit cracks ; and the 
twist split a strong supporting beam in one of the shops in 
Manchester Road. The stalls in the open market were 
much shaken ; and one of the hucksters ran round his can- 
vas with the intention of catching the youngster who was 
playing him a trick. So far as I can judge, the magnitude 
and duration of the shock were very similar to those in the 
earthquake which passed through this district in July, 
1839 . 
Professor Roscoe, F.R.S., reported to the meeting the 
important discovery made by MM. Graebe and Liebermann, 
of the artificial preparation of alizarin, the colouring matter 
of madder, from anthracene or hydrocarbon found in coal 
tar. It appears that the formula given for alizarin many 
years ago by Dr. Schunck, viz. C 14 H 10 O 4 , corresponds closely 
to the composition which the substance is now found to 
possess, viz., C 14 H 8 0 4 We are as yet unaware how alizarin 
is obtained from anthracene C 14 H 10 . The artificial colouring 
matter appears to possess all the properties of the madder 
alizarin, and the ordinary mordants yield the well known 
colours in every respect identical with those obtained in the 
well known processes of madder dyeing. The importance 
of this discovery can hardly be over estimated. 
