ApRL II, 1907 | 
INA TOE 
569 
OUR ASTRONOMICAL COLUMN. 
Comet 1907a.—No. 4165 (March 26) of the Astrono- 
mische Nachrichten contains a new set of elements and 
an ephemeris for comet, 1907a (Giacobini), calculated by 
Herr M. Ebell from places observed on March 9, 12, 
and 16. According to the elements, the perihelion 
passage took place on March 26, and, as shown by the 
ephemeris, the comet’s brightness is decreasing, now being 
less than half what it was at the time of discovery. The 
position of this object for April 11 is a=6h. 14m., 
3=+4° 47’, and the comet is travelling in a nearly due 
northerly direction, its calculated position for May 6 being 
6h. 10m.+13° 42’. 
THE BRIGHTNESS OF THE SKY NEAR THE SuN’s Limp.— 
With an apparatus described in No. 4164 (March 25) of 
the Astronomische Nachrichten, Prof. Ceraski, at Moscow, 
determined the relative intensities of the light at the sun’s 
limb and the atmospheric illumination very near the limb 
on November 3 and 4, 1906. On the former date the 
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mean value of the ratio -““"-" _ at _the east and west 
atmosphere 
limbs was 31-4, and on November 4 it was 38-4, values 
far below those which Prof. Ceraski expected to find. 
Prof. Ceraski points out that this ratio might be 
employed as a term of comparison in evaluating the 
relative intensity of the corona. Using the method de- 
scribed by him in No. 4106 of the Astronomische 
Nachrichten, the coronal light could be compared with 
that of a standard lamp, which might, after the eclipse, 
be measured against the illumination of the atmosphere 
at a determined point in the sky. Thus the illumination 
of the sun’s edge could be compared indirectly, in 
graduated steps, with that of the corona. 
RapiaAL VeELocity oF 7 Piscitum.—This star was 
announced by Mr. Lord as a possible spectroscopic binary 
having a long period, but Prof. Campbell was unable to 
find any variation in the line-of-sight velocity. The 
binary character is now confirmed by plates secured at the 
Dominion Observatory at Ottawa, the range of velocity 
so far detected being from +5-4 km. to +21-4 km. per 
second, and there are indications that the period is a 
comparatively short one. 
a Draconis has also been observed, and the velocity 
curve practically completed; the period is between fifty 
and fifty-one days, and the velocity ranges from —53 km. 
to +35 km. per second. 
In the case of 1 Orionis, a considerably larger range of 
velocity than that announced by the discoverers was 
found, that already observed extending from —50 km. to 
+100 km. (the Journal R.A.S. Canada, No. 1, vol. i.). 
SIMULTANEOUS OBSERVATIONS OF 
Bulletin de la Société astronomique de France for 
December, 1905, it was suggested that simultaneous 
observations of Jupiter should be made by as many 
volunteer observers as could be obtained, and that the 
results, obtained with many different kinds of instruments 
and under varied conditions, should be communicated to 
and coordinated by the society. 
One hundred and seventy-two observers made observ- 
ations at prearranged hours on various dates between 
January 2 and 20, 1906, and the first batch of results is 
now discussed by M. Mascart in the April number of the 
Bulletin, the general conclusions derived from all the 
observations on one day being given, together with repro- 
ductions of the original drawings for January 2, 3, 4, 
and 5, 1906. 
Tue Sun AS A VARIABLE Star.—At the meeting of the 
Royal Astronomical Society held on March 8 Prof. Turner 
briefly discussed the light curves of a number of variable 
stars, and showed that there existed a sequence in their 
forms. In most cases the minimum falls later than mid- 
way between two maxima, in others earlier, and on 
arranging the curves of thirty-one variables it was found 
that the sun falls into the sequence. Seeking some ex- 
planation for this arrangement, Prof. Turner has evolved 
the interesting suggestion that the form of the curve may, 
to some extent, depend upon the position of the star’s 
axis in regard to the line of sight; thus we view the sun 
NO. 1954, VOL. 75 | 
Jupiter.—In the 
from a point lying nearly in the plane of its equator, but 
the poles of other stars may be turned towards us, whilst 
in other cases we may be looking normally at mid- 
latitudes. 
An analysis, from this point of view, of the suitable 
data given in Chandler’s catalogue of variable stars led 
to the tentative result that whilst the stars where we look 
directly at the equator are distributed in all galactic lati- 
tudes, those of which we see the polar regions are absent 
from the neighbourhood of the galactic poles. As a purely 
speculative interpretation of this difference, Prof. Turner 
suggests that the axes of the stars may be nearly parallel 
to the plane of the Milky Way, an arrangement which 
would, of course, account for the result found (the 
Observatory, No. 382, April). 
EFFECTS OF PRUNING ON FRUIT TREES. 
HE scientific work carried on at the Woburn Experi- 
mental Fruit Farm, by the Duke of Bedford and 
Mr. Spencer U. Pickering, F.R.S., is of great value to 
horticulturists, who usually follow rule-of-thumb methods 
in much the same way as the British farmer cultivates his 
crops. The fifth report of the Woburn Fruit Farm, noticed 
in Nature of September 7, 1905 (vol. Ixxii., p. 461), 
showed that several cherished ideas as to the proper treat- 
ment of fruit trees need modification, and that operations 
which are generally supposed to be beneficial to growth 
and fruit-bearing are really prejudicial to both. Measure- 
ments of leaves, trees and fruits, and weighings of the 
fruit, led to the conclusions that heavy thinning of the 
fruit is of no advantage; hard pruning is unprofitable ; 
summer pruning is undesirable; and root pruning in- 
jurious. An explanation was also found of the fact that 
carelessly planted trees, though weak at first, ultimately 
make more growth than trees carefully planted. 
The observations described in the fifth report of the 
Woburn Fruit Farm have since been extended, and the 
new resulis and conclusions are dealt with in the seventh 
report recently issued. As the conclusions are based on 
experimental evidence, they are, of course, of far greater 
value than mere expressions of opinion; and though they 
apply only to particular trees in a particular soil, they 
suggest that the ways of the practical gardener are not 
always wise. The empirical horticulturist believes that 
“* srowth follows the knife,’’ but by measuring and weigh- 
ing trees it has been found that the less a fruit tree is 
pruned the larger and heavier it becomes, even when 
allowance is made for the amount of wood removed in the 
annual pruning of the normal trees. The fruit crops of 
trees are also increased as the amount of pruning is 
diminished, so it appears that the less pruning done the 
better is the result both as regards growth and fruit. 
These conclusions, however, apply only to healthy and 
established trees. Transplanted, injured, or ailing trees 
may be regarded as prematurely old trees which tend to 
form an excessive number of fruit-buds and increased wood 
formation. The obvious way to prevent this is to prune 
hard; and the experiments at Woburn show clearly that 
if transplanted trees, that is, trees which have been 
checked in their development, are cut back at once, the 
operation results in the starting of many dormant buds 
followed by a clean, vigorous growth. Hard pruning also 
results in increased branch-formation in the case of mature 
trees, the effect being thus the opposite to what is found 
when the pruning is on young trees in the full vigour of 
growth. 
The experiments show, in fact, that with trees, as with 
animals, there are certain periods in their life-history 
characterised by certain distinct differences of behaviour. 
All the results obtained at Woburn can be explained by 
remembering that any cause which disturbs the balance 
between the root and branch systems at any period of 
growth is followed by an effect which will adapt the 
organism to the new condition. The observations are thus 
not only of importance to practical horticulturists, but are 
also of scientific interest. The summary of the report, re- 
1 Seventh Report of the Woburn Experimental Fruit Farm. By the 
Duke of Bedford, K.G., and Spencer U. Pickering, F.R.S. Pp. 56. 
(London ; Eyre and Spottiswoode, 1907.) Puice rs. 6¢. 
