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arch above the stream. Nothing can surpass the 

 strength and beauty of, some modern stone bridges 

 those, for instance, which span the Thames as it 

 passes through London. Iron bridges have been made 

 with arches twice as large as those of stone, the 

 material being more tenacious, and calculated to form 

 a lighter whole. That of three fine arches, between 

 the city of London and South wark, is a noble speci- 

 men; and, compared with the bridges of half a cen- 

 tury ago, it appears almost a fairy structure of light- 

 ness and grace. The great domes of churches, as 

 those of St Peter's in Rome and St Paul's in Lon- 

 don, have strength on the same principle as simple 

 arches. They are, in general, strongly bound at the 

 bottom with chains and iron bars, to counteract the 

 horizontal thrust of the superstructure. The Gothic 

 arch is a pointed arch, and is calculated to bear the 

 chief weight on its summit or key-stone. Its use, 

 therefore, is not properly to span rivers as abridge, 

 but to enter into the composition of varied pieces 

 of architecture. With what effect it does this, is 

 seen in the truly sublime Gothic structures which 

 adorn so many parts of Europe. The following 

 are instances, in smaller bodies, of strength ob- 

 tained by the arched form: A thin watchglass 

 bears a very hard push ; a dished or arched wheel 

 for a carriage is many times stronger to resist all 

 kinds of shocks than a perfectly flat wheel ; a full 

 cask may fall with impunity where a strong square 

 box would be dashed to pieces; a very thin globu- 

 lar flask or glass, corked and sent down many 

 fathoms into the sea, will resist the pressure of 

 water around it, where a square bottle, with sides 

 of almost any thickness, would be crushed to pieces. 

 We have an illustration, from the animal frame, of 

 the arched form giving strength, in the cranium or 

 skull, and particularly in the skull of man, which is 

 the largest in proportion to its thickness: the brain 

 required the most perfect security, and by the 

 arched form of the skull, this has been obtained 

 with little weight. The common egg-ohell is 

 another example of the same class: what hard 

 blows of the spoon or knife are often required to 

 penetrate this wonderful defence provided for the 

 dormant life ! The weakness of a similar substance, 

 which has not the arched form, is seen in a scale 

 from a piece of freestone, which so readily crumbles 

 between the fingers. To determine, for particular 

 cases, the best forms of beams and joists, and of 

 arches, domes, &c., is the business of strict calcu- 

 lation, and belongs, therefore, to mathematics, or 

 the science of measures. It was a beautiful pro- 

 blem of this kind, which Mr Smeaton solved so 

 perfectly in the construction of the far-famed Eddy- 

 stone light-house. See Light-House. 



STRENGTH, FEATS OF. Doctor firewater, 

 in his work on Natural Magic, gives some striking 

 instances of muscular strength, and also of the 

 effects produced by applying the principles of the 

 mechanical powers to the human frame, from which 

 we extract the following: Firmus, a native of 

 Seleucia, who was executed by the emperor Aure- 

 lian for espousing the cause of Zenobia, was cele- 

 brated for his feats of strength. In his account of 

 the life of Firmus, who lived in the third century, 

 Vopiscus informs us, that he could suffer iron to be 

 forged upon an anvil placed upon his breast. In 

 doing this, he lay upon his back, and, resting his 

 feet and shoulders against some support, his whole 

 body formed an arch, as we shall afterwards more 

 particularly explain. Until the end of the sixteenth 

 century, the exhibition of such feats does not seem 



to have been common. About the year 1703, a 

 native of Kent, of the name of Joyce, exhibited 

 such feats of strength in London and other parts of 

 England, that he received the name of the second 

 Samson. His own personal strength was verv 

 great; but he had also discovered, without the aid 

 of theory, various positions of the body, in which 

 men even of common strength could perform very 

 surprising feats. He drew against horses, and 

 raised enormous weights; but as he actually ex- 

 hibited his power in ways which evinced the enor- 

 mous strength of his own muscles, all his feats 

 were ascribed to the same cause. In the course of 

 eight or ten years, however, his methods were dis- 

 covered, and many individuals of ordinary strength 

 exhibited a number of his principal performances, 

 though in a manner greatly inferior to Joyce. 

 Some time afterwards, John Charles van Eckeberg, 

 a native of Harzegerode, in Anhalt, travelled 

 through Europe, under the appellation of Samson, 

 exhibiting very remarkable examples of his strength. 

 This, we believe, is the same person whose feats 

 are particularly described by doctor Desaguliers. 

 He was a man of the middle size, and of ordinary 

 strength; and, as doctor Desaguliers was convinced 

 that his feats were exhibitions of skill, and not of 

 strength, he was desirous of discovering his methods ; 

 and, with this view, he went to see him, accom- 

 panied by the marquis of Tullibardine, doctor 

 Alexander Stuart, and doctor Pringle, and his own 

 mechanical operator. They placed themselves 

 round the German so as to be able to observe accu- 

 rately all that he did; and their success was so 

 great, that they were able to perform most of the 

 feats the same evening by themselves, and almost 

 all the rest when they had provided the proper 

 apparatus. Doctor Desaguliers exhibited some of 

 the experiments before the royal society, and has 

 given such a distinct explanation of the principles 

 on which they depend, that we shall endeavour to 

 give a popular account of them. 1. The performer 

 sat upon an incline^ board with his feet a little 

 higher than his hips. His feet were placed against 

 an upright board well secured. Round his loins 

 was placed a strong girdle with an iron ring in 

 front. To this ring a rope was fastened. The 

 rope passed between his legs through a hole in the. 

 upright board, against which his feeixwere braced, 

 and several men or two horses, pulling on the rope, 

 were unable to draw him out of his place. 2. He 

 also fastened a rope to a high post, and, having 

 passed it through an iron eye fixed in the side of 

 the post some feet lower down, secured it to his 

 girdle. He then planted his feet against the post 

 near the iron eye, with his legs contracted, and, 

 suddenly stretching out his legs, broke the rope, 

 and fell backwards on a feather bed. 3. In imita- 

 tion of Firmus, he laid himself down on the ground, 

 and when an anvil was placed upon his breast, a 

 man hammered with all his force a piece of iron, 

 with a sledge-hammer, and sometimes two smiths 

 cut in two with chissels a great cold bar of iron 

 laid upon the anvil. At other times, a stone of 

 huge dimensions was laid upon his belly, and 

 broken with a blow of the great hammer. 4. The 

 performer then placed his shoulders upon one chair, 

 and his heels upon another, forming with his back- 

 bone, thighs, and legs, an arch. One or two men 

 then stood upon his belly, rising up and down while 

 the performer breathed. A stone one and a half feet 

 long, one foot broad, and half a foot thick, was 

 then laid upon his belly and broken by a sledge- 



