Proceedings. 171 



and, after making a short calculation, I felt convinced it would answer the purpose 

 with proper management and attention. 



This was the cause why I constructed it in the way I did, making what I con- 

 sider an imperfect piece of machinery. 



The whole consisted of a crab, chain, gutta percha tube, and bell, with the 

 necessary supports for its suspension. 



The crab was single piirchase, the power ganied being equal to about 6 to 1. 



The chain was half-inch, and capable of sustaining a working load of three and 

 a half tons. 



The air pump consisted of a single cylinder of 7 inches diameter and 14 stroke, 

 and was worked in the same way as an ordinary fire engine, the piston being a 

 common packed one, had two valves passing through it opening downwards, which 

 were immediately closed by two spnal springs on the completion of the up-stroke, 

 after the air had passed through them m. its ascent, and iilled the cylinder, the 

 piston forcing the whole contained within through the passage in the bed-plate 

 and valve on the outside, which opened upwards, and preventing any air from 

 escaping back again that had previoiisly passed tlnough iato the gutta percha tube 

 leading to the Bell. 



The Bell was composed entnely of wrought iron boiler plates, rivetted together 

 and corked, as an ordinary boiler would be, the plates being l-4th of an inch in 

 thickness at the upper part, increasing in thickness to the bottom ; the lower plate 

 being 3-8ths, having in addition to the plate a wrought u'on flat hoop rivetted all 

 round to stiffen the edge. There was also another loose hoop about 15 mches 

 from the bottom of the Bell, (the diameter being about 16 inches greater) ; to this 

 hoop eight large pieces of cast iron were attached, each weighing about 1501bs. 

 The hoop" and weights were then connected by suspension rods to a cross bar 

 placed edgeways upon the top of the Bell ; to this bar two rods were also connected 

 which supported it, and fom* others forming a pyramid, to the apes of which a 

 single block was attached, by means of which we were enabled to raise or lower the 

 BeU to any height or depth by the winch placed at the contrary end of the 

 pontoon. You vidll perceive by the above arrangement the weights employed to 

 sink it had no comiection whatever with the BeU, causing no strain whatever upon 

 the rivets, or plates, of which it was composed. 



Not having complete apparatus I laboured under great difficulties, and ran a 

 very great risk of endangering the lives of those parties at work in the BeU. Its 

 deficiency consisted, first, in having but one air-pump, which rendei'ed it impossible 

 to secure a continuous current of an, and in case of any breakage or derangement 

 of the parts, the supply would be entu'ely cut off. 



Secondly, in the thinness of the metal of which the BeU was composed, being 

 obhged to attach large masses of iron to the hoop, near the bottom, to keep it 

 steady, and sink it ; and not being able to make any but an uneven surface, caused 

 considerable risk, from its liability to become entangled with the stumps, and various 

 other substances with which we were continually coming in contact, thereby 

 causing the risk to be even greater in this case than the former. 



