288 REPORT— 1885. 
(a) The expansion of a salt solution is the more uniform the more 
concentrated it is. The curves representing the expansion approach more- 
nearly straight lines as 7 increases. 
() At low temperatures salt solutions expand more than water, at. 
higher ones less; there is thus a point at which the coefficient of expan- 
sion is the same as that of water. This temperature is little, if at all, 
affected by the concentration. They are as follows :— 
NAD ceo. 552602 
KO . . 50°= 55° 
NaNO, . . 80°—100° 
ie Bei. 
(y) The volumes at different temperatures may be satisfactorily ex- 
pressed by interpolation formule of the form 
V=100,000+ fa+#28; 
Where #/=#°—20°, and a and £ constants depending on the salt and the 
value of mn. In 126 determinations only two differed from the calculated 
se #2 
100,000’ 100,000 
The constants a and (6 are thus related; as 7 increases a increases, but 3 
decreases ; the expansion approximating more and more to 100,000-+a ?’. 
The results confirm in most points those of Kremers, and it is hoped 
when the experiments are complete that it will be possible to establish the- 
connection between the vapour pressures and the molecular volumes, as. 
has already been attempted by Tammann in an incomplete form. 
value by more than the mean error being less than 
Report of the Committee, consisting of Professor Sir H. E. Roscor, 
Mr. J. N. Lockyer, Professors Dewar, WoLcorr Gisps, LIVEING, 
Scuuster, and W. N. Hartiey, Captain Abney, and Dr. MARSHALL. 
Warts (Secretary), appointed for the purpose of preparing anew 
series of Wave-length Tables of the Spectra of the Elements and 
Compounds. 
Tue present Report contains the completion of the tables of the spectra 
of the elements, and a portion of those of the spectra of compounds. 
The measurements are given in ten-millionths of a millimetre (or tenth- 
metres), and are based upon the measurements of the Fraunhofer lines 
by Angstrém for the whole visible rays, and the extension of the same 
series of measurements into the ultra-violet portion of the spectrum made 
by Cornu und other observers. It will be well to repeat here the funda- 
mental values of wave-length of the chief solar lines. The small correc- 
tions indicated at page 29 of Angstrém’s Memoir, ‘ Le Spectre Normal 
du Soleil,’ have been applied to his numbers—but they are uncorrected 
for the dispersion of air. Hence the numbers in the tables represent, 
wave-lengths in air,of 760™™ pressure at Upsala, and 16° C. temperature. 
The numbers taken from Thalén’s ‘Détermination des Longueurs d’Onde 
des Raies Métalliques’ in the same way have had applied to them the 
necessary small corrections to bring them into harmony with the numbers 
finally adopted by Angstrém as ‘ Valeurs définitives’ (pp. 25 and 31-32). 
