618 

the cause of cancer we are dealing with two factors— 
(1) a predisposing cause, probably due to auxetics, 
which are set free by injury, X-rays, and atrophy, 
which are actually injected into the tissues by the 
commodities, and which occur in excess in the tissues 
generally in persons above the age of forty—the cancer 
age; and (2) an exciting cause, the nature of which 
has still to be worked out, and which supervenes on 
top of (1). Whatever this exciting cause is, it is re- 
sponsible for the metastasis and death. It would seem 
that a combination of the two causes is essential, 
namely, that cancer is due to local manuring of the 
tissue; either one or other by itself appears only to 
cause benign tumour formation. Hi: €. Ross: 
The John Howard McFadden Research Fund, 
The Lister Institute of Preventive Medicine, 
Chelsea Gardens, S.W. 

Dr. Ross’s letter raises the question as to whether 
photosensitive molecular systems of the nature of those 
contained in the gelatino-bromide emulsion might not 
be affected by auxetics and augmentors applied under 
suitable conditions. If such effect was found to exist, 
the facts he adduces would not be out of line with the 
view that some molecular change within the cell finds 
a counterpart in actions progressing in the unstable 
film under the stimulus of radiation or equivalent 
chemical influences. 
The reasons set forth by Dr. Ross against the theory 
that soot acts mechanically appear convincing, 
although I cannot agree with him that this substance 
can be described as soft and floury. There has always 
been difficulty in accounting for its peculiar virulence 
on the mechanical theory. Some time ago I looked 
for the emanation of radium in soot, but found very 
little. If it acted like charcoal we would expect a 
large amount, in which case Dr. Lazarus-Barlow’s 
views would find additional support in this direction. 
I may add that some of the suggestions put forward 
in the lecture which was in part issued in Nature 
of June ro have been under investigation here for 
some time. J. Jory. 
Trinity College, Dublin. 

The Magnetic Storm of June 17 and Solar 
Disturbances. 
As my final note on Dr. Chree’s letter in Nature of 
July 22 and Mr. Buss’s of July 29 may I remark 
that, so far as I am aware, there is no rule, 
‘*‘One spot, one storm’? On the contrary, a 
disturbed area of the sun’s surface may be 
connected with a series of successive, or inter- 
mittent disturbances, as it is carried round by the 
sun’s rotation. When the same region reappears at 
the next synodical rotation, and sometimes, if it sur- 
vives as an active region, for several synodical rota- 
tions, it will continue to be associated with a series 
of magnetic disturbances at each rotation. For 
instance, in 1898, January 11 to July 31, a disturbed 
region of the sun, which subsisted during eight rota- 
tions, was associated with not one only, but with 
several magnetic storms, at each successive reappear- 
ance. Nor is the selection of such a region arbitrary, 
when there happen to be several other disturbances 
at the same time on the sun. The selection is condi- 
tioned by the activity of the region, and by its posi- 
tion relatively to the position of the earth, when pro- 
jected on the sun. So far as I am aware, mere 
statistical enumerations of sun-spots, or total areas of 
sun-spots, and their relations to magnetic storms, take 
no account of these important considerations. 
The efficiency of a disturbed region of the sun, 
marked by sun-spots, is greater on the descending 
NO. 2388, VOL. 95] 
NATURE 

[AUGUST 5, 1915 
portion of the sun-spot curve than even at maximum. 
The reason of this is, because after the maximum, the 
mean latitude of the spots is falling towards the sun’s 
equator, and since the heliographic latitude of the 
earth varies between +7°, the earth is placed in a 
more favourable position to be affected by a solar 
disturbance. In the twenty-five years, 1889-1913, there 
were seven years in which the mean daily projected 
or disc-area of sun-spots was greater than 1000 107° 
units, and eighteen years in which it was less. In the 
seven maximum years there was a mean of too dis- 
turbances a year, and a yearly mean daily disc-area 
of 1537°7 units. The ratio between these two numbers, 
or what may be termed the “‘efliciency ratio,’’ is 
0-065. Similarly for the eighteen years in which the 
mean daily disc-area was less than 1000 107° units, 
the mean number of disturbances was 73°7 per year, 
and the yearly mean daily disc-area was 378-9 units, 
which gives an ‘‘efficiency ratio” o-195, three 
times as great as in the maximum years. Of these 
eighteen years, twelve were on the descending arm of 
the sun-spot curve. These numbers show that the 
position of a disturbed region of the sun relatively to 
the earth is more important than its size. In addition, 
the character of the spot has to be considered. 
To apply these principles of selection to the case of 
the magnetic storm of June 17. Since the beginning 
of 1913, all the sun-spot disturbances, with insigni- 
ficant exceptions, had been confined to regions above 
12° on each side of the solar equator. From June 12 
to June 21 an entirely new active group of spots 
covering a considerable area appeared on the sun’s 
equator. The heliographic latitude of the earth was 
also most favourable. The first very great magnetic 
storm of the present solar cycle toolk place on June 17, 
preceded by a disturbance on the 16th, and followed by 
a disturbance on the 18th. 
With regard to the 27-day period shown in the quiet 
magnetic days, I associated them with the whole solar 
hemisphere only in this sense, that, as a rule, when 
there is no solar spot, there is no magnetic disturb- 
ance. The proviso is added, because a region of the 
sun which may be free from spots may, by the 
presence of faculz or flocculi, still continue to be 
magnetically active, after the spots have died away. 
In several cases the region will continue to be mag- 
netically active, on account of the appearance of new 
spots near the facule or flocculi belonging to the 
former disturbance. A. L. Corrie. 
Stonyhurst College Observatory, Blackburn, 
Lanes., July 23. 
Science and Food-Supply. 
In connection with the proposed “ Mobilisation of 
Science,’ it may be of importance for Great Britain 
to direct the attention of her scientific men to the 
possibility of increasing the food-supply produced 
in the country. Here she might very hopefully call 
upon her’ organic chemists for aid; by asking them 
to devise means for extracting nutritive material from 
the crops which are not now used for food. 
Nearly all vegetable matter contains the nutritive 
elements needed. In a certain sense, for example, 
‘all flesh is grass”’; but we cannot digest vegetable 
matter of that kind directly; it must be put through 
a chemical process before it can be assimilated. The 
process usually adopted is to put it into the stomachs 
of animals, and then we eat the animals. Through 
the intervention of cattle and sheep we thus eat grass 
in the form of beef and mutton. 
In a similar manner, deer and goats and many 
other animals which are not limited to a grass diet 
convert moss, and shrubs, and bark, and small 
branches into nutritive material for man. The wood 
