180 Mr Morren on the Influence of Light on the quality 
We have no thermometrical record for August, but in rela- 
tion to the other warm months, we may observe that the 
greatest heat did not exceed 59°. Even that height was rarely 
attained ; and the 26th and 27th of May was as warm as any 
day throughout the year, the thermometer standing, on each 
of these days, at 59°. The only day in June which equalled 
that heat was the 17th, and no day in July exceeded 58°. 
Mr Wilson's observations on the zoology of St Kilda accord 
with those of Mr Macgillivray. The clergyman made men- 
tion of an extremely beautiful foreign bird, of considerable 
size, which was observed to frequent the island one season for 
several weeks. Its plumage “ littered in the sun,” and was 
of a resplendent green and blue colour. This was, probably, 
a stray example of the roller (Coracias garrula), a bird well 
known in Germany, and not unfrequent in Sweden during 
summer. 
We shall only further observe, that the population of St 
Kilda, at the period of Mr Wilson’s visit in August last, 
amounted precisely to 105.—Ep. 
Researches on the influence which Light and the Green-coloured 
Organic substance often found in Stagnant Water exercise 
on the quality of the Gases contained in the latter. By Mr 
A. Morren, 
Tue author has had occasion to analyse the water of many fountains 
and wells in the town of Angers, as well as to examine the gases they 
contain. He has convinced himself that these waters, as well as 
those of the Loire and Maine, have nearly the twenty-fifth part of their 
volume, as is generally the case with well aired running water in its nor- 
mal state, formed of a gas composed of 82 per cent. of oxygen and 68 per 
cent. of azote. On one occasion, in the summer, he analysed the gas ex- 
tracted by boiling from the water ofa fish pond which had a greenish ap- 
pearance, and was surprised to find that it contained from 56 to 58 per 
cent. of oxygen. On resuming this experiment the following day, only 
25 per cent. of oxygen was produced in the morning ; about mid-day, 48 
per cent. ; and at five o’clock in the evening 61 per cent. The volume 
of air dissolved increased with the proportion of oxygen; the carbo- 
nic acid likewise varied, but the quantity of azote continued very nearly 
constant. 
By continuing these experiments, he perceived that, independently of 
the evident influence of light on the oxygenation of the water, the cool- 
