122 



Anniversary Meeting. 



[Nov. 30, 



" ration were attended to ; and in the measures of the deviations the 5th 

 " and 6th spectra were generally taken ; his experience indicates that in 

 " taking these measures it is best to have the intervals of the grating not 

 " very close, but covering a surface of some magnitude : the deviations are 

 " less, but the spectra brighter. 



" The result of these measures is given in six beautiful maps, extending 

 " from B to H 2 . The places of the lines are laid down on a scale, not of de- 

 " viations, but of wave-lengths, in which the unit is a ten-millionth of a 

 " millimetre. 



" The advantage of this can scarcely be overrated ; for in other maps 

 " the scale depends on the refractive indices of the prisms and their adjust- 

 " ments, so that no two are comparable ; while at ordinary temperatures and 

 " pressures the wave-lengths are invariable. 



" In addition to hydrogen he found in the sun thirteen metals, of which 

 " titanium has 200 lines. The total amount of metallic lines is nearly 800, 

 " including most of the strong lines ; so that probably the sun has few ele- 

 " ments which are not found on our earth. There are some strong lines 

 " between E and G whose origin as yet is unknown ; one coincides with a 

 " line of bromine, whose presence is not probable. There are three strong 

 " magnesium lines not present in the sun ; and oxygen, nitrogen, and carbon, 

 " so common here, are not detected there. He thinks the sun is not hot 

 " enough to make the first two luminous; carbon in the circuit of his battery 

 "shows no lines of its own, but those of its compounds. He doubts 

 "Pliicker's notion of the same substance having different spectra, and 

 <c thinks that the change is merely due to the increased temperature, which 

 " makes faint lines intense — and is disposed to think that the pillar-like 

 " appearance observed in some star-spectra indicates a lower temperature 

 " than the black sharp lines which occur in others. 



" The aurora and zodiacal light have in common a line (X=5567) whose 

 " origin is yet unknown. 



" It must be admitted that this list is the exponent of intellectual power 

 " of first-rate excellence, and of additions to our knowledge which are not 

 *' only intrinsically valuable, but are also eminently suggestive of ulterior 

 * c progress. Nor can his claim to priority of entrance into this wondrous 

 '* region be disputed by any unprejudiced judge. Though Stokes and Thom- 

 " son nearly at the same time drew the same conclusion as to absorption, 

 ' { and even satisfied themselves of the identity of D with the sodium lines — 

 " though Stewart, and still more successfully Kirchhoff, again brought it 

 " before the public three years after, yet this is what happens to every 

 " inventor or discoverer : others follow in his track, some perhaps more 

 " successfully than himself ; but his right remains untouched." 



The ' Porcupine ' having been again placed by the Admiralty (for three 

 months of the summer of 1870) at the disposal of the physicists and 

 naturalists engaged in researches on the temperature of the sea at great 

 depths, and on the nature of the sea-bottom and of the life existing in its 



