/ 



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of the most celebrated. It has been noticed by grave philosophers, and j 



sung by poets, as may be seen in the following epigram of Claudian : ; 



; 



"Jupiter, in parvo com cerneret ffithera vitro, 



Risit, et ad snperos talia verba dedit : 

 Hnccine mortalis progressa potentia cur 

 Ecce Syracusii ludimar arte eenis." 



Archimedes wrote a description of this machine, under the name of 

 " Sphaeropffiia ;" but it is lost, and with it everything respecting the na- 

 ture of the sphere has perished. 



The burning mirrors, by which he is said to have set fire to the Ro- 

 man vessels in the harbor of Syracuse, were long considered as fabulous. 

 But BufFon showed how, by placing a number of small mirrors so that 

 every one of them should reflect the image of the sun to the same point, 

 heat enough might be produced to kindle wood at the distance of one 

 hundred and forty feet. 



The protracted defence of Syracuse against the Romans, chiefly in 

 consequence of the wonderful mechanical inventions of Archimedes, is 

 too well known to be enlarged on here. 



If we except the discoveries of Archimedes in statics and hydrostatics, 

 hardly any other branch of physical science was much cultivated by the 

 ancients. They have made, indeed, considerable progress in the knowl- 

 edge of acoustics, so far as music is concerned. In optics they can 

 scarcely be said to have made any progress of consequence ; and, in as- 

 tronomy, very little till the time of Hipparchus, who may be considered 

 as, in some measure, the founder of that sublime science. 



Dr. Thomson lays down two methods by which the physical sciences 

 are advanced : observation and experiment ; and the application of math- 

 ematical reasoning to deduce new facts from principles already estab- 

 lished. We give his remarks on observation and experiment, in which 

 he exhibits an analysis of the theory of Bacon on this subject : 



It was not to be expected that mankind should at first make any rapid 



progress in investigating the laws which regulate the changes that take 



place in the material world. The objects were too numerous and too 



varied, and escaped his attention by their very regularity. Everywhere 



? in the early ages of the world, we meet with descriptions of prodigies 



