MECHANICS AND USEFUL ARTS. 83 



place had a pane of glass left whole. At Woolwich, four miles dis- 

 tant, door and window frames and sashes were smashed in, portions 

 of ceiling and wall shaken down, many persons were violently thrown 

 out of their beds, and several persons were injured. 



At Chatham, 25 miles distant, the windows in the great workshops 

 were violently shaken, and doors were forced open. 



At Deptford, four or live miles off, 150 gaslights in a large factory 

 were blown out at once. The same thing occurred at a police station 

 in Whitechapel, London. The people of Soharn, 80 miles from Erith, 

 heard a noise resembling thunder, and felt a shock which they attrib- 

 uted to an earthquake. The sound of the tremendous report spread 

 even further, for it was supposed to be distant thunder at a place 04 

 miles away. In the Crystal Palace in London, some doors were 

 violently forced open, arid paintings knocked down from the walls. 



The niDJt remarkable effect of the explosion was upon animals in 

 the large region around. The mortality among canary birds for 



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miles ar urnd was very great ; they dropped from their perches and died 

 of fright, or of the concussion. Parrots were badly frightened, and 

 dropped from their perches to the bottoms of their cages, refusing to 

 speak for some hours. Dogs, cats and other animals manifested 

 symptoms of the greatest alarm. For many miles from Erith the 

 cattle in the fields, at first struck dumb and motionless at the stunning 

 report, presently set off in the wildest excitement, racing around the 

 enclosures, and could not be quieted for some hours. All the churches 

 f jr 1-3 inik's around, and most of them for 20 miles, have suffered by 

 broken windows and cracked walls. 



Siu-h w^re some of the phenomena of this terrible explosion. 



A writer in the London Times thus speculates on the probable effect 

 of the explosion of 2,000 tons of powder, the amount stored in the 

 government magazines at Purileet, 16 miles from London : 



2,000 tons of powder would occupy 75,000 cubic feet of space, 

 or equal to a pile 100 feet long, 40 feet wide and 20 feet high, 

 quite the size of an ordinary parish church. As powder, at the 

 moment of its explosion, exerts an elastic force of 1,000 times the 

 pressure of the atmosphere (15,000 pounds to the square inch), the 

 ignition of this quantity would instantaneously liberate a force equal 

 to 14,000,000 tons. As the vibrations of force radiate equally in all 

 directions, like those of light and heat, it necessarily follows that its 

 intensity diminishes in proportion as the circle of its radiation in- 

 creases in diameter. Thus, taking the direct distance from London 

 to Purfleet as 16 miles, an explosion at the latter magazine would, 

 by the time it reached town, be distributed over 10,000,000,000 

 square yards of surface, and, therefore, the mechanical effect of the 

 shock to the houses in London would be a little over 31 pounds per 

 square yard of surface, or 220 pounds on the front of an ordinary 

 average dwelling-house. This would be augmented to a slight 

 extent from the fact that the power of the shock would not radiate 

 downward in consequence of the earth, and would react in other 

 directions. 



The quantity of powder exploded at Erith on the occasion of the 

 late catastrophe was 104,000 pounds, or 1,733 cubic feet ; this, prob- 

 ably, produced a force of 800,000 tons, and this, radiating to London, 



