70 7 
x 885-1 Sanitary Agency of Light. 
of the centrifugal tendency that the globe creates in one 
half of its period of rotation, corresponding tides being thus 
produced on the opposite sides of the earth. There are 
many things operating incidentally upon the water which 
produce variations in the periods and elevation of the tides 
in different places on each portion of the earth. A correct 
knowledge of the law of fluids will at once demonstrate the 
cause of the whole phenomenon, and it is by understanding 
the natural tendency of fluids, and that of all other sub- 
stances, when subjected to a centrifugal force, that the 
present explanation of the phenomenon will become esta- 
blished beyond the possibility of refutation. 
II. SANITARY AGENCY OF LIGHT. 
f ^HE discovery of M. Duclaux described in the last num- 
K* ber of this journal for October under the above title 
^ would seem to be a necessary corollary of the fadts 
made known by Downes and Blunt in 1877 and 1878, and 
embodied in two papers read before the Royal Society, and 
entitled respectively “ On the Effedt of Light upon Badteria 
and other Organisms,” and “ On the Influence of Light upon 
Protoplasm,” the conclusion being stated as follows, “ Light 
is inimical to, and, under favourable circumstances, may 
wholly prevent the development of these organisms, its 
adtion upon Bafteria being more energetic than upon the 
mycelial and torulaceous fungi, which are prone to appear 
in cultivation fluids. The author went further, and showed 
that this effedt was due to oxidation, which, so far as proto- 
plasm and certain other substances of organic origin were 
concerned, was stimulated by light, and ended either in the_ 
extinction or great depression of the vitality of organisms 
submitted to it. Moreover they succeeded in localising t ie 
adtion in the spedtrum, their conclusions being thus stated. 
“ It is probable, therefore, that if the phenomena weie 
represented by a curve, the maximum elevation would be 
found in or near the violet, a rapid descent occurring in the 
blue or green, after which the line of cuive is maintained 
more or less as far as the visible red in other words, the 
