16 HISTORY OF ASTRONOMICAL DISCOVERY. 



been erected to contain a sundial with eight faces, meeting the four cardinal and four 

 intermediate points of the horizon, and a clepsydra ; and, by an ingenious contrivance, it 

 would appear that the latter was sometimes made to divide the day into twelve equal 

 parts, the aperture through which the water flowed contracting or enlarging according as 

 the length of the natural day increased or diminished. 



A great variety of instruments were constructed by the Alexandrians. Astrolabes, or 

 armillary spheres, were used in the observance of solar and sidereal phenomena. These, 

 in the hands of the Arabs, at a subsequent period were largely improved, and made upon 

 a gigantic scale. Whether any knowledge was possessed of the means by which the 

 natural sight is now assisted in the contemplation of distant objects, is a controverted 

 topic. From some obscure intimations found in the ancient writers of bodies circulating 

 in the universe invisible to the naked eye, it has been conceived that the satellites of 

 Jupiter and Saturn are meant, having been discovered by the aid of instruments analogous 

 to the telescope. Sir W. Drummond assigns a knowledge of that instrument to the 

 Greeks, Chaldeans, and Hindus ; but though some strong facts may be quoted in favour 

 of the former, the evidence is not sufficient to warrant the inference. In enabling the 

 eye to bear the brilliancy of the solar light, when directed towards that luminary, 

 various methods were adopted. Aristotle speaks of mirrors being used in his time, 

 probably meaning thin metallic plates finely polished. Ptolemy mentions vessels of oil 

 being employed in viewing eclipses, and Seneca refers to the medium now common, that 

 of smoked glass. 



We now take leave of the ancient world, bewildered by the apparently involved and 

 disorderly movements of the heavens, having hold of no clue by which to arrive at the 

 discovery of their harmony, "puzzled with mazes and perplexed with errors." The 

 economy of the universe was a sealed book to the eye of antiquity the theory of its best 

 scholar a dream, at utter variance with the truth. The book had been shut for thousands 

 of years previous, and it remained closed for more than a thousand years afterwards. 

 Yet there were not wanting some lofty minds who clearly perceived the discordance 

 between the interpretation given and the fac,ts observed, after all that ingenuity and 

 application had done towards a reconcilement, and who seem to have indulged the anti- 

 cipation of the appearance of a person able to open the volume and read the perfect 

 coherence of its contents. Such was Seneca the philosopher. " How many things," he 

 remarks, " are beyond the reach of human intelligence ! and how small is the part of 

 the universe accessible to our knowledge ! even the Deity himself is no better known to 

 us." But, as if inspired with the spirit of prophecy, he observes : " The time will come 

 when posterity will be surprised that we could be ignorant of things, the knowledge of which 

 might have been so easily acquired, and some one will at length arise who shall teach men 

 the paths of the comets, their magnitude and number, and why they deviate so far from 

 the routes of the planets." How has the anticipation been realised the prophecy been 

 fulfilled ! It is somewhat remarkable that he who in his Natural Questions thus expressed 

 himself, should, in a similarly happy vein, have treated another topic in the tragedy of 

 Medea as follows: " Eras shall come in late years, in which ocean may loosen the bonds 

 of things, and a spreading continent expand, and Tethys reveal new regions, nor Thule 

 be the boundary to the lands." If the former passage strongly reminds us of Copernicus 

 and Halley, the latter does so equally of Columbus and Vasco de Gama, 



