126 
The Use of the Hygro-Spectroscope 
floods in both France and England (not predicted by the 
barometer) were noticed by him in connection with a peculiar 
band in the spectrum under dates July 19th and 26th, 1875. 
Prof. Smyth vividly described in * Nature ’ (vol. xii., pp. 231, 
252) the phenomena then observed, how the dark band near 
D was found the forecast of a drenching afternoon following 
the fine opening of a Scotch holiday in Edinburgh; and how, 
on another occasion, it became the ‘ spectroscopic prevision of 
rain with a high barometer.’ Then followed observations in 
May, 1876, to the same effect in France, especially at 
Marseilles, where the rain-band was seen in the spectrum, 
and followed by rain, to the surprise of the natives, who 
consulted only the public barometer and thermometer, and 
found none predicted. In February, 1878, appeared the 
fourteenth volume of the ‘ Edinburgh Astronomical Observa¬ 
tions ’ (1870-1877), and here, under the head of ‘Meteoro¬ 
logical spectroscopy in the small and rough,’ we have the 
subject treated in a most complete and elaborate manner, 
and illustrated by a set of engravings of spectra. The 
Scottish Meteorological Society’s ‘Journal’ (N. S., Nos. 51, 
52) also contains contributions by Prof. Smyth on the 
subject. Again, in ‘Nature’ of July 1st, 1880 (vol. xxii., 
pp. 194-5), the subject of ‘ rain-band spectroscopy ’ is dealt 
with in a condensed and epitomised form very acceptable to 
the reader, who doubtless will recognise the identity of the 
‘ Edinburgh Experimenter’ in this useful contribution on the 
subject.” 
It will at once be seen from the above that Prof. Piazzi 
Smyth, the talented and kindly Astronomer-Royal for Scot¬ 
land, was the real discoverer of the “rain-band,” but I consider 
that a great deal of praise is due to Mr. Rand Capron for 
popularising the subject by means of the before-mentioned 
monograph. In June of this year I was induced, from some 
letters that I had communicated to the ‘ Times,’ to read a 
paper on this topic before the Royal Meteorological Society. 2 
I endeavoured to show in this—1st, that the rain-band is not 
the only feature to take into account in the sky spectrum; 
2nd, that to successfully forecast rain the spectroscope ought 
to be directed towards that quarter from which the wind is 
2 [Since published (Quart. Journ. Meteor. Soc., vol. ix. (No. 48), p. 234), 
under the title, “ The Spectroscope as an Aid in Forecasting Weather.” 
Ed.] 
