116 W. W. Jacques— Velocity of very Loud Sounds. 
substances. There is, however, a number of bodies which 
permit of the inquiry into their simple or complex nature being 
made in such a manner that the presence of impurities will be 
to a certain extent negligable. I have brought this subject 
before the Royal Society at its present stage, in the hope that 
possibly others may be induced to aid inquiry in a region im 
which the work of one individual is as a drop in the ocean. If 
there is anything in what I have said, the spectra of all the 
elementary substances will require to be re-map and re- 
mapped from a new standpoint; further, the are must replace 
the spark, and photography must replace the eye. A glance 
at the red end of the spectrum of almost any substance incan- 
descent in a voltaic arc in a spectroscope of large dispersion, 
and a glance at the maps prepared by such eminent observers 
as Huggins and Thalen, who have used the coil, will give an 
idea of the mass of facts which have yet to be recorded and 
reduced before much further progress can be made 
In conclusion I would state that only a small part of the 
work to which I have drawn attention is my own. ‘In some 
eases I have merely, as it were, codified the work done by 
other observers in other countries. With reference to that 
done in my own laboratory, I may here repeat what I have said 
before on other occasions, that it is largely due to the skill, 
atience, and untiring zeal of those who have assisted mé. 
he burthen of the final reduction, to which I have before 
referred, has fallen to Mr. Miller, my present assistant ; while 
the mapping of the positions and intensities of the lines was 
done by Messrs. Friswell, Meldola, Ord, and Starling, who have 
successively filled that post. 
I have to thank Corporal Ewings, R.E., for preparing the 
various diagrams which I have submitted to the notice of this 
Society. 
Art. XII.—On the Velocity of very Loud Sounds; by W1LLIAM 
W. Jacques, Fellow of the Johns Hopkins University. 
Ir is very well known that the velocity of a musical sound 
is, within very wide limits. sensibly independent of its intensity 
and of its pitch. The experimental proof of this is that a piece 
of music, played by a military band at a considerable distance 
comes to the ear of the observer with its harmony entirely 
undisturbed. ii, 
A consideration of the theory of the propagation of a musical 
sound too, shows that for sounds such as we ordinarily hear, 
im which the change of density from the rarified to the com 
