‘DECEMBER 21, 1916] 
The district. studied extends: over Virginia, the Caro- 
linas, Georgia, and northern Florida, ranging from 
the Appalachian summits to the sea-level. Lists of 
species characteristic of the various regions are given, 
and in the systematic part of the paper variation is 
studied so far as possible in relation to geographical 
conditions. 
“A Systematic Account of the Prairie-Dogs,” 
by N. Hollister, has lately been issued (No. 40, ‘‘ North 
American Fauna,’’ U.S. Dept. Agric. Biol. Survey). 
The genus Cynomys is divided into two subgenera 
and five species, in the descriptions of which nearly 
goo specimens have been utilised. There are com- 
parative photographs of skulls and _ distributional 
maps. It seems a pity that in valuable zoological 
memoirs such as this the ridiculous misnomer ‘‘ dog” 
should be stereotyped for these animals, which, accord- 
ing to the author, are ‘‘true ground-squirrels, or 
spermophiles.”’ 
A CATALOGUE of the earthquakes felt in the. Philip- 
pine Islands in the year 1915 has recently been pub- 
lished in the U.S. Weather Bulletin. The number of 
shocks recorded during the year is 170, only forty- 
eight of which reached the degree 4, or a higher 
degree of the Rossi-Forel scale, though fifty-seven 
were registered at the Manila Observatory. One 
earthquake, which occurred on March 12 in south-east 
Luzon, though it attained an intensity of only 6-7 
{that is, of less than destructive intensity), disturbed 
' an area of about 45,000 square miles, and was recorded 
at seismological observatories all over the world. 
Capt. GourLay’s note on a phosphorescent centi- 
pede, recorded in Nature of November 23 (p. 233), has 
elicited some further facts worth putting on record. 
They have been sent us by Mr. S. Priest, hon. sec., 
Dartford Naturalists’ Field Club, and relate to the 
experiences of members of the club residing at Stone 
and Dartford. He cites two cases of centipedes, seen 
during October and November, emitting a trail of 
light as they crawled along, and exuding phos- 
phorescent matter on to the fingers when handled. 
Another specimen left ‘‘trail-like drops of green light ”’ 
behind it. The light in this case was so brilliant as 
to show through the handkerchief in which it was 
placed after capture. Finally, Mr. Priest cites a case 
of this luminosity persisting in a crushed specimen. 
THE purification of oyster-beds by means of chlor- 
inated water has formed the subject of experiment by 
the Board of Fish and Game Commissioners, Cali- 
fornia. According to California Fish and Game (vol. 
ii., No. 4), a trace of calcium hypochlorite can be 
passed through the gills and alimentary canal. of the 
oyster without any detrimental effect upon the animal, 
while any water-borne disease, such as typhoid, is 
effectually destroyed. In the sameissue it is urged that 
more use should be made of the immense quantities 
-of the edible mussel to be found along the rocky shores 
‘of Humbolt County. Not only, it is insisted, do they 
provide a most nutritious food when eaten in the 
fresh state, but they are scarcely, if at all, less palat- 
able when pickled. Finally, protective measures have 
been framed for the ‘‘Alabone,” or Haliotis, which 
thas been almost exterminated for the sake of its shell. 
It is urged that this mollusc can be made to produce 
pearls of extreme beauty by inserting foreign bodies 
‘between the mantle and the shell. 
Butietin No. 61 of the Agricultural Research Insti- 
tute, Pusa, gives an interesting review by Mr. A. 
Howard of the bearing of soil aeration upon crop pro- 
‘duction, with especial reference to the agriculture of 
India. Striking illustrations of the importance of this 
NO. 2460, VOL. 98] 
NATURE 
315 
factor have been furnished by the experimental work 
of recent years in that country. The requirements of 
nodule-producing leguminous crops for supplies of 
nitrogen and oxygen in the soil render soil aeration 
a factor of obvious importance in their growth, and 
experience with the gram and indigo crops and in the 
general practice of green manuring fully bears this 
out. The distribution of gram in India follows the 
occurrence of well-aerated soils. Experiments at Pusa 
have demonstrated that the growth of gram in 
deficiently aerated soil can be greatly improved by the 
simple expedient of incorporating considerable quanti- 
ties of tile fragments with the soil. The indigo plant 
provides an even more striking instance of dependence 
upon soil aeration, and much of the money expended 
in attempts to improve the production of natural indigo 
might have been saved had more attention been paid 
to the needs of the plant in this respect.- Soil aeration 
has been shown also to have an important bearing 
upon the maturation and quality of grain, fruit, 
vegetables, and tobacco. Various practical applications 
of soil aeration are indicated, including more rational 
irrigation, manuring, improvement of crops and cattle, 
and the development of wheat and rice areas. With 
efficient aeration adequate nitrogen supplies can be 
derived directly from the air by bacterial activity, 
whilst soil fungi will liberate supplies of available 
phosphates and potash. 
Tue twelfth memorandum of the Health of Muni- 
tion Workers Committee deals with the output of 
munition workers in relation to hours of work, and 
the question has been investigated from a statistical 
point of view by Dr. H. M. Vernon. It was found 
that, when the number of working hours per week 
was increased beyond a certain level, the output was 
not correspondingly increased, but tended to fall off 
owing to the occurrence of ‘‘ broken time”’ from sick- 
ness or fatigue. The number of working hours per 
week which yielded the maximum output varied with 
the character of the work. For moderately heavy 
labour, the maximum output was attained with sixty 
hours’ work a week, whereas those engaged in light 
labour worked as much as seventy hours a week in 
order to reach their maximum output. Dr. Vernon 
points out that the production of a maximum output 
day after day by the worker must impose a consider- 
able strain, and that in many cases the strain 
became too great to be borne and the worker had to 
drop out altogether. Hence the optimum length of 
the working week, suited for peace times, is consider- 
ably shorter than that mentioned, although the prin- 
ciple of graduating the number of hours to the type 
of work performed still holds good. The memo- 
randum also gives instances of considerable delay in 
starting the day’s work and of a similar slackening 
just before the day’s work ceases, and it is pointed 
out that the elimination of these causes of lost time 
would increase the worker’s output without lengthen- 
ing his working day. 
Tue September number of Terrestrial Magnetism 
and Atmospheric Electricity contains the results of the 
measurements of the deviation of the magnetic com- 
pass from true north made by the survey ship Car- 
negie during her circumnavigation of the Antarctic 
continent between December, 1915, and June, 1916. 
The great bulk of the observations relate to latitudes 
between 50° and 60° south, but in the neighbourhood 
of Australia many observations were taken north of 
this belt. According to the new survey, the British 
Admiralty Chart gives the deviation to the west in the 
South Atlantic a fraction of a degree too great, and 
the error south of the Cape of Good Hone rises to 6°. 
: In the south of the Indian Ocean the chart over 10° 
