176 
NATURE 
[Apri 18, 1912 
designations of each star, Mr. Backhouse gives the 
magnitude as shown in eleven different publications, 
and then gives a weighted mean, the system of 
weighting being explained in the preface. Those 
amateur astronomers who have recently been 
struggling with the intricacies of various systems, in 
trying to understand the published magnitudes of 
Nova Geminorum No. 2, will appreciate the usefulness 
of such a catalogue. The work contains 186 quarto 
pages, and is published by Hills and Co., Sunderland. 
Tue PHoroGraAPHic TRansir.—The results of further 
experiments with a photographic transit, carried out 
by Prof. Hirayama during 1907-08, are published in 
the second fascicule of vol. v. of the Annales de 
lV’ Observatoire astronomique de Tokyo. They show 
that there is no change of the mean error either with 
the declination or with the photographic magnitude, 
and that the instrument is capable of producing very 
valuable results. 
Puysics anD AstropHysics.—In No. 12 (1911) of 
the Bulletin de la Classe des Sciences, Académie Royale 
de Belgique, is published a most interesting lecture 
by M. J. E. Verschaffelt, in which the author shows 
how deeply the physical sciences are indebted to the 
results secured in astronomy for the suggestion, or 
the confirmation, of many of their fundamental con- 
cepts. For examples he quotes, inter alia, Newton’s 
and Kepler’s work on gravitation, Roemer’s deter- 
mination of the velocity of light reinforced by Brad- 
ley’s discovery of aberration, and the idea of the 
pressure of light suggested by the solar repulsion of 
cometary matter. It is interesting to note that at the 
earth’s surface the pressure of the solar radiation on 
each square metre of a blacix body amounts only to 
two-thirds of a milligram. In conclusion, M. Ver- 
schaffelt strongly expresses the hope that astrophysics 
may be officially included in the programme for the 
doctorate in the Belgian universities. 
Tue Parattax OF Nova Lacert, 1910.—From 
observations made at Yerkes Observatory during 
December, 1910, and January, 1911, Prof. Slocum 
finds the relative parallax of Nova Lacertz to be 
+o0'013”+0'014". As the average parallax of his com- 
parison stars, according to Kapteyn’s table, may be 
taken as o'005”, the absolute parallax obtained for 
the nova is +o°018’. Too great an accuracy cannot 
be claimed for this result, but if it is correct the out- 
burst producing the nova occurred some 180 years 
ago. (Astrophysical Journal, vol. xxxv., No. 2.) 
NOVA GEMINORUM NO. 2. 
jaXes account of the discovery of Nova Geminorum 
No. 2 is given by Herr Enebo in No. 4564 of the 
Astronomische Nachrichten. After observing the 
variable SV Tauri, at Sh. 32m. (M.E.T.) on March 12, 
Herr Enebo’s eye, wandering over the neighbouring 
constellation, was arrested by the appearance of a com- 
panion to @ Geminorum which he had not noticed 
when observing that region four days earlier; the 
new object was then of magnitude 431 on the Pots- 
dam scale. Herr Enebo’s subsequent observations 
indicate that the nova was at its brightest when dis- 
covered, or on March 13, when he estimated the 
magnitude as 4°23, although other observers found it | 
to be about 3°5 on March 14. 
Herr Jost publishes a list of comparison stars, 
ranging from 4'6 to 83 in magnitude, and gives the 
colour of each so that comparisons with the nova 
mav be facilitated. Dr. Wolf publishes a photo- 
graphic chart of the nova region taken in January, 
1909, and gives the magnitudes of surrounding stars 
down to about 9'5. 
NO. 2216, vor. 89] 
Dr. Guthnick reports a brightening of o'4 mag. on 
March 22, accompanied by a diminution in the red- 
ness of the star. The red colour is quite marked, 
and makes the nova stand out from the other stars in 
a field of 14 degrees; the Rev. T. E. R. Phillips is 
of the opinion that it is one of the reddest stars he 
has ever seen. : 
A communication from Prof. E. C. Pickering, pub- 
lished in No. 45605 of the Astronomische Nachrichten, 
states that Dr. Curtiss found the magnitude on 
March 13°7 to be 39, the spectrum then being like 
that of Nova Aurige. The Harvard photographs 
of March 13, however, showed only dark lines, and 
Prof. Pickering suggests that the bright lines seen 
with a slit spectroscope at the Ann Arbor Observatory 
may have been too narrow on that date to appear on 
the Harvard objective-prism spectra. Dr. Curtiss’s 
observations showed a recessional velocity of 5 kms. 
for the dark reversals of the H and K lines. 
Prof. Pickering also states’ that on March 16 the 
spectrum was of the normal nove type, and the 
nebular lines were first seen. Better weather evidently 
prevailed in the United States than in England on 
March 13 and 14, for Prof. Pickering reports that 
seven good photographs of the spectrum were secured 
on each of those nights. 
At the Hamburg Observatory spectrograms were 
obtained on March 20, 23, and 27, and many broad 
bright lines, especially the hydrogen series HS to Hy, 
are shown. Prof. Schwassman identifies two of the 
other bright lines with lines at AA 4230 and 4176 in 
Vogel’s spectrum of Nova Aurigz, while a third lies 
halfway between AA 4315 and 4288. On March 27 
the bright K line was indistinct, but other bright lines 
were more marked than on the previous dates. Prof. 
Schwassman identifies three of these, at AA 4583, 
4557, and 4525, with lines of Fe, Ba, and Ti. 
Greenwich observations on March 15, reported in 
The Observatory (No. 447, April) showed the visual 
brightness to be one-quarter of a magnitude, and the 
photographic one magnitude, fainter than #@ Gemi- 
norum. The photographic magnitudes were secured 
by placing a grating, made of zinc strips, with spaces 
of equal width, in front of the object glass, and are 
as follows :—March 20, 5°5; 21, 60; 26, 61; 28, 63: 
29, 6°5; 31, 60, and April 1, 6'5. 
At Cambridge, reports Prof. Newall, the nova on 
March 14 was at least one magnitude brighter than 
6 Geminorum; as the estimated magnitude on March 
15 was 42, it would appear that the nova lost 1% 
magnitudes in 24 hours. A series of photographs 
of the spectrum shows interesting changes in the 
relative brightness of the lines, in the structure of 
the hydrogen lines, and in the appearance on March 
22 of a second pair of broad bright and dark lines a1 
the more refrangible side of each hydrogen line. 
According to observations by M. Luizet, published 
in L’Astronomie for April, the nova decreased in 
brightness to the extent of one magnitude between 
toh. on March 15 and 7h. 50m. on March 16. 
M. Baume Pluvinel’s spectra observations on March 
21 show each of the hydrogen lines H& to He doubled 
or trebled, and all displaced towards the red.” 
Dr. Easton reports a second recrudescence of 
brightness on April 9, when, at oh. 15m. (G.M.T.), 
the H.P. magnitude was 670, but the brightening 
probably occurred earlier than this, although bad 
weather prevented Dr. Easton observing it. A 
secondary maximum is plainly shown, in Dr. Ebell’s 
series of observations, for March 30 (Astronomische 
Nachrichten, No. 4564). Dr. Strémgren’s series 
shows that on March 24, the previous maximum, the 
colour became bluish instead of red as previously. 
