359 
NATURE 
[JUNE 6, 1912 
secondary effects, the bombardment can in several 
ways reasonably account for the observed phenomena 
connected with the earth light. 
THe Minor Pranetr to1r M.T.—When the minor 
planet 1911 M.T. was discovered by Dr. Palisa, -its 
direct motion suggested proximity to the earth, which 
might prove useful in parallax determinations. In 
No. 4573 of the Astronomische Nachrichten Dr. 
Palisa now gives elements, calculated by Messrs. 
Haynes and Pitman under Prof. Leuschner, which 
give the perihelion distance as 1-:1273 or 1-1643, and 
the aphelion distance as 2-8629 or 2:5043; both sets 
of elements would probably be modified by further 
investigations, but the former appears to fit better the 
observations yet compared with it. 
THE ROYAL OBSERVATORY, GREENWICH. 
apie annual visitation of the Royal Observatory 
took place on Saturday last, June 1, when the 
Astronomer Royal presented to the Board of Visitors 
his report of the work done during the year ended 
May to. 
Many of the instruments were opened up for in- 
spection, with assistants in charge to explain the 
many wonderful devices which are an essential part 
of the equipment of a great observatory of the pre- 
sent day, Visitors were greatly attracted by a new 
feature, the floating zenith telescope designed by the 
late Mr, Bryan Cookson, and lent to the observatory 
by the Cambridge Observatory authorities for a 
period of seyen years. Similar to an ordinary zenith 
telescope in principle, the V’s which carry the 
vertical telescope are carried by an iron ring floated 
on mercury, so that, with the two axes properly 
adjusted, verticality is automatically secured. 
Observations of pairs of stars by Talcott’s method 
are being made to determine the variation of lati- 
tude and the aberration constant, and by combining 
the results for several years it is hoped to secure a 
very satisfactory determination of the aberration. 
This instrument replaces the old reflex zenith tube, 
which is incapable of giving the accuracy now 
required, 
The fine summer enjoyed last year allowed the 
meridian observations of stars between 24° and 32° 
north declination, begun in 1906, to make good pro- 
gress, but the part of 2h. to 6h. R.A. is yet somewhat 
under-observed. During the twelve months nearly 
14,000 transits were observed with the transit circle, 
besides the usual observations of nadir and _ level. 
From the 1910 observations, using the Pulkowa re- 
fractions, 38° 31' 21-83” was derived as the value of 
the colatitude, and the reduction of the observations 
of the sun gives a correction to the tabular value of 
the obliquity of the ecliptic of +007’. From the 
observations of the moon’s limbs and the crater 
Mosting A, with the transit circle and altazimuth, 
the mean error of the moon’s tabular place for 1910 
was —o0:537s. in R.A. and +0-32” in declination. 
An investigation of the large discordance between 
north polar distances given by altazimuth in reversed 
positions points to faults in the eye end of the instru- 
ment, and this is being replaced by a new part. At 
the same time, a travelling-wire micrometer is to be 
introduced for observing R.A. and a printing micro- 
meter for the zenith distances. 
More than 700 observations of double stars, mostly 
pairs showing relative motion, were made with the 
28-in. refractor, nearly 300 of the observed pairs being 
separated by less than 10”. The 26-in. refractor, 
carried with the 30-in. reflector and the  6-in. 
Franklin-Adams lens on the Thompson equatorial, is 
NO. 2223, VOL. 89] 
being devoted to the determination of the parallaxes 
of stars in the Greenwich Astrographic Zone, photo- 
graphs on the same plate being made at intervals of 
six months of all stars showing large proper motions. 
For this purpose an attempt was made to secure a 
better adjustment of the crown and flint components 
of the objective, to give greater accuracy, and it has 
been found necessary to order a new cell, carrying 
necessary adjustments, for the crown lens. : 
The work, with the 30-in. reflector, of securing 
photographic standards for the magnitudes of the 
stars counted on the Franklin-Adams_ plates, is 
delayed by the scarcity of nights at Greenwich on 
which the transparency of the sky is the same at 
the pole as at a similar altitude in the south. Varia- 
tions of focus when the mirror was directed to 
different parts of the sky were also troublesome, but 
it is hoped to eliminate this trouble by using a sub- 
sidiary device for examining visually the focus. 
Among the interesting exhibits displayed on Satur- 
day was a series of photographs taken with this 
instrument on October 11, 1911, to locate the new 
minor planet M.T., believed to be very near to the 
earth. At first the examination of these plates failed 
to reveal the object, but later, when further data 
were received, images believed to be of the planet 
were found on three plates. 
The Franklin-Adams 6-in. lens is used for deter- 
mining photographic magnitudes of bright stars in 
the Greenwich zone, all of which can be covered by 
eighty-four fields; of these, fifty-five have been 
photographed and forty-one of the plates measured. 
A 30° prism placed in front of this lens enabled 
photographs of the spectrum of Nova Geminorum (2) 
to be taken on several dates. Some of these ex- 
hibited on Saturday show excellent definition and 
great changes in the general nature of the spectrum, 
although the dispersion is small. The changes of 
magnitude of the nova were shown by photographs 
taken with the astrographic equatorial having a 
coarse wire grating placed in front of the object 
glass. With a grating made of 1-65 mm. wire, with 
spaces from centre to centre of 5 mm., the first 
diffraction images were sensibly round, and differed 
from the primary image by nearly two magnitudes. 
Photographs of the sun were secured on 256 days, 
as against 152 days in the previous twelve months. 
Part of this increase was due to a greater amount of 
bright sunshine received and part due to an arrange- 
ment whereby work is commenced at 7 a.m. in the 
summer. The series of photographs for 1911 is com- 
plete except for January 1, on which date no photo- 
graph appears to have been taken at any of the four 
contributing observatories. All the evidence points to 
the present epoch as one of minimum solar activity, 
and advantage was taken of the lull to discuss the 
thirty-eight years’ observations now available for 
determining the position of the sun’s axis. The 
result shows that Carrington’s position requires but 
a very small correction. 
Two observers are going from Greenwich to 
Cruzeiro (lat. 22° 39’ S., long. 44° 58’ W.) to observe 
the Brazilian eclipse of the sun on October 10. Their 
equipment will include the Thompson 9-in. corona- 
graph and a quartz spectrograph especially fitted for 
recording the extreme ultra-violet part of the chromo- 
spheric spectrum. 
Magnetic observations were carried out as usual, 
and showed that in 1911 there were no days of 
“sreat’? magnetic disturbance. For t1g11_ the 
elements determined were :— 
Mean declination eS S SROs 
;, horizontal force 0'18529 (in C.G.S. units) 
», dip (with 3-in. needles) 66° 52’ 6” 
