THE ATMOSPHERE. 



in Spain, in the year 1538, he saw, in the presence of 

 the Emperor Charles V. and about ten thousand speo 

 tators, two Greeks let themselves down under vrater, ifc 

 a large inverted kettle, with a burning light, and rigo 

 up again without being wet.' 



After this time it became more known, and is spoken 

 of in the works of Lord Bacon, who describes its effects, 

 emd commends its value in facilitating submarine labor. 



Among the greatest results of the use of this machine, 

 may be considered those of William Phipps, a native of 

 this country, who, in the year 1683, under leave of 

 Charles II., formed a project for searching for a rich 

 Spanish ship sunk on the coast of Hispaniola. After 

 many trials, he succeeded in bringing up from the depth 

 of six or seven fathoms, treasures to the value of 

 ,200,000 sterling. He afterwards received the honor 

 of knighthood, and died in London in 1693. 



Diving bells are made of different forms and materials. 

 When made of wood, they are generally about five feet 

 high, four feet broad at the top, and six feet at the bot- 

 tom. When made of iron they are sometimes of this 

 form, but more frequently are made to resemble the 

 lower half of a cone. The one used at Hov.'th, neat 

 Dublin, is an oblong iron chest, six feet long, four broad, 

 and five high, and weighs about four tons. It has two 

 Seats capable of holding four persons. 



Their descent in water depends on the law of Hydro- 

 statics, that l a body immersed in a fluid, displaces 

 exactly its own bulk of it.' And consequently, that it 

 may be sunk, it must be made heavier than a bulk of 

 water equal to itself in size. Therefore, in calculating 

 the weight requisite to sink a bell, we first ascertain 

 the number of cubic feet it contains, and knowing the 

 average weight of a cubic foot of water to be about 

 sixtytwo and a half pounds, we multiply the bulk by the 

 weight of the water, and the quotient will be the power 

 requisite to balance the upward pressure. An excess 

 of weight is then added to facilitate its descent. 



We are particularly indebted to Dr Halley for the 

 improvements in this machine, and for the means where- 

 by individuals are enabled to continue a long time under 



