506 Chronicles of Science. [July, 
spark traverses without modifying it. Between these two extremes, 
surfaces are obtained on which the spark produces more or less com- 
plete stratification of very varied appearance. ‘The designs traced by 
the electric current are transparent on an opaque surface, so that they 
can be copied directly on positive photographic paper. 
It has not hitherto been possible to obtain a deflection of the mag- 
netic needle by the secondary current of the Leyden battery, but by 
means of an apparatus which he calls the “ electrical valve,’ M. P. 
Riess* has succeeded in obtaining evidence of this deflection, and has 
deduced the convenient rule that by means of the electrical valve, and 
in any position, the secondary current of the Leyden jar deflects a mag- 
netic needle in the direction of a current proceeding from the dise to 
the point of the valve. M. Reiss describes a numerous series of ex- 
periments which show in a very striking manner the occurrence of the 
extra current in the circuit of the battery itself, and are not less con- 
clusive than are the previous experiments of the author on the heating 
of the branches. 
X. SANITARY SCIENCE. 
Tuart the weather exercises a considerable influence over the health 
of individuals and communities has long been a favourite article in 
the popular creed, and this belief has been embodied in many a wise 
saw and pithy proverb. But it is not only in such apophthegms that 
this conviction of the influence of the weather upon disease and 
mortality has been expressed ; it has formed the subject of many 
laborious and learned memoirs, and since the time when Hippocrates 
penned his celebrated treatise ‘On Airs, Waters, and Places,’ it has 
taken a permanent position in the medical literature of all civilized 
lands. In more modern times the researches of Casper, Quételet, 
Boudin, Guy, Sir James Clark, and many others, have done much to 
throw light upon the effects produced by external causes on the con- 
stitution of the human frame. During the past year, the literature of 
this subject has received an addition, in the form of an elaborate 
memoir ‘ On the Influence of Weather upon Disease and Mortality,’ + 
by Dr. R. E. Scoresby-Jackson, in which an endeavour is made to 
treat the subject in a somewhat more exact manner than has often 
been attempted. His investigations are restricted to the climate and 
death-rate in the eight principal towns in Scotland, and the data he has 
employed in the course of his inquiry have been furnished by the 
collected returns from the stations of the Meteorological Society of 
Scotland, and from the mortality tables constructed from the returns 
made by the Scottish Registrar-General. The period over which his 
investigations have extended is six years. At the outset of his me- 
moir he lays down the following proposition, one, we think, to which 
* «Phil. Mag.,’ series iv. p. 313. 
+ Transactions of the Royal Society of Edinburgh, 1863, and reprint. 
