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HISTORY OF SCIENCE. 



FIG. 193. THE GREAT NEBULA IN ORION. 



examined by the elder Herschel under his highest telescopic powers 

 without its showing any appearance of being capable of resolution 

 into stars. But Lord Rosse's reflector and the great refractor of the 

 Cambridge (U.S.) Observatory have to a considerable extent resolved 

 this nebula into a multitude of stars. The spiral arrangements of such 

 nebulas as that in Comes Venatid would appear to afford some support 

 to the hypothesis of Laplace ; but astronomers must scan these sin- 

 gular bodies with close attention for many ages before they can hope to 

 recognize signs of such changes as the hypothesis requires. Granting, 

 however, the truth of the hypothesis and a sufficiently long duration 

 for the human race and human records, it is not too much to expect 

 that these records may yet describe the phenomena which present 

 themselves while a nebula is being transformed into a solar system. 



The rapid progress of astronomy in modem times has been largely 

 due to improvements of the instruments of observation and of measure- 

 ment. The delicacy with which angular magnitudes can now be 

 estimated would excite the astonishment of an ancient astronomer 

 were one " to revisit the glimpses of the moon." The division of gra- 

 duated instruments which had, in the previous century, undergone 

 successive improvements in the hands of Sharp, Graham, Bird, and 

 Ramsden, was carried to thegreatest pitch of perfection by Troughton, 

 the celebrated instrument maker. EDWARD TROUGHTON (1753 



