the peesident's addeess. 313 



systems of meridian observations of the stars and planets, which 

 have already supplied sufficient materials from which the future, 

 as well as the past history of the heavens has been written, thus 

 fulfilling the objects of the foundation of the Observatory, as 

 expressed in the original warrant of Flamsteed, the first 

 Astronomer Royal, ' ' to apply himself with the most exact care 

 and diligence in the rectifying the tables of the motions of the 

 heavens and the places of the fixed stars, in order to find out the 

 so much desired longitude at sea, for the perfecting the art of 

 navigation." 



I must now claim your attention for a few minutes while I 

 explain, very briefly, a few of the principal deductions derived 

 from recent researches in spectrum analysis, by which the 

 astronomer has been assisted in building up, step by step, what 

 is now believed to be the most probable theory of the physical 

 constitution of the sun, the fixed stars, nebulae, and meteorites. 

 For it has been undoubtedly proved from these researches, that 

 several metals and gases, either in a solid, liquid, or vapour 

 form, are common to the sun and earth. "We know with absolute 

 certainty that the sun contains similar elements to those existing 

 in the earth, with this distinction, that in the photosphere of 

 the sun, iron, copper, and other metals are found in a gaseous 

 form, and not as here in a cold and solid state. The great body 

 of the sun is therefore composed of intensely hot gases, corres- 

 ponding to different metals ; outside these there are clouds 

 consisting not of the vapour of water as on the earth, but of the 

 vapours of different gases. What is more remarkable, similar 

 terrestrial substances as in the sun also form, in a greater or less 

 degree, the principal material elements of most of the fixed 

 stars whose light has been spectroscopically examined, even of 

 those situated in the remotest parts of space. This unity of 

 operation appears to be existent throughout the universe, so far 

 as light enables us to have cognizance of distant objects. 



It is not my intention to enter into a detailed scientific des- 

 cription of the theories or methods of observation employed in 

 spectrum analysis, further than to state, that all our knowledge 

 of the peculiar constitution of the heavenly bodies is based on 

 the existence of certain dark or bright bands or lines which are 



