64 
THe Tevituric Lines IN THE SOLAR SPECTRUM.—M. 
Stefanik is proceeding with his researches on the direct 
observation of the infra-red portion of the spectrum, and 
publishes an account of his most recent results in a com- 
munication to the Paris Academy of Sciences (Comptes 
rendus, No. 17). After briefly reciting the history of our 
knowledge of the telluric bands and lines, the author 
describes the two spectroscopes with which he carried out 
his researches at Chamonix, at the Grands-Mulets, and on 
the summit of Mont Blanc. In each case he employed the 
red screens which he has previously described, and by this 
means was able to see the region of the spectrum which 
extends from about B to 1 w. On July 21, at the Grands- 
Mulets, he observed the setting sun with his prism spectro- 
scope, and found that as the sun sank lower the group 
a was unequally strengthened in parts, whilst several feeble 
bands became visible between a and A. The groups Z, X, 
and II were successively reinforced, notably more so as the 
sun sank into the haze gathered at the horizon. Similar 
observations made with the grating spectroscope at the 
summit of Mont Blane on July 30 gave similar results, and 
a feeble band appeared between the groups A and Z. The 
increase in intensity of the groups Z and m was so con- 
siderable that their telluric origin was very obvious. Zenith 
observations revealed changes which in general were of 
the opposite character. At all three stations M. Stefdnik 
obtained a number of photographs when the sun was 
highest and at the horizon, respectively, with both spectro- 
scopes. 
Tue NUMBER OF THE VISIBLE Stars.—The total number 
of stars usually supposed to be visible in the largest tele- 
scopes and.on the best photographs is about one hundred 
million, but according to a computation recently made by 
Mr. Gore this number must be accepted as the outside 
maximum. To obtain his results Mr. Gore made a 
number of counts on the photographic prints given in the 
late Dr. Roberts’s volume of stellar photographs, and found 
that the average number of stars per square degree was 
4137 in the Milky Way, 1782 near the Milky Way, and 
408 in the non-galactic regions. Combining these results 
with the estimated areas of galactic and non-galactic 
regions published by Prof. E. C. Pickering, he obtained 
as the grand total of visible stars the number 64,184,757. 
This is probably smaller than the actual total, as some of 
the fainter star images would probably be lost in the re-_ 
production of Dr. Roberts’s photographs. 
Clusters and nebulze were avoided in making the counts, 
so that Mr. Gore’s total will have to be increased on this 
account. In another count the average richness of the 
irregular clusters came out as 5752 stars per square degree, 
but this is far below the average richness of the globular 
clusters, one of which, w Centauri, shows 25,000 stars per 
square degree (Observatory, No. 376). 
Stars witH PEcuLiaR Spectra.—In No. 4129 of the 
Astronomische Nachrichten Dr. H. Ludendorff discusses 
the spectra of the stars R Coronze Borealis, 12 Canum 
Venaticorum, and 72 Ophiuchi, which he and Dr. Eberhard 
have photographed with the three-prism spectroscope 
(No. iv.) of the Potsdam Observatory. The remarkable 
feature in the spectrum of R Coronz is the non-appearance 
of the hydrogen lines HB, Hy, and Hd; as the H and K 
lines are broad, the absence of He cannot be affirmed, but 
on a smaller scale spectrogram the ultra-violet lines of 
hydrogen do not appear. From the measurement of about 
thirty or forty lines on each of five spectrograms, Dr. 
Ludendorff finds the radial velocity of this star to be about 
+246 km. as compared with Prof. Frost’s value of 
+14 km. The present values were, however, obtained 
during a period when the star was at its normal bright- 
ness, whereas Prof. Frost’s referred to a period when it 
was fainter. It thus appears that the radial velocity may 
vary during the epochs of magnitude changes. 
In the spectrum of 12 Canum Venaticorum, Dr. Luden- 
dorff suspects changes in various chromium and iron lines. 
The magnesium line A 4481 also appears to vary, and, 
whilst he can find no reason for the variation, Dr. Luden- 
dorff suggests that this may be analogous to a similar 
phenomenon which Sir Norman Lockyer has pointed out 
in the spectrum of a Andromedz, both stars being of the 
Markabian type. 
NO. 1933, VOL. 75| 
NATGORE 
| Kong Observatory in Nos. 4130-1 
| NOVEMBER 15, 1906 
AN INTERESTING VARIABLE STaR.—In No. 4126 of the 
Astronomische Nachrichten Prof. Barnard publishes the 
results of his visual observation of a variable situated in 
the brightest part of the cluster M3 (N.G.C. 5272). 
Observations were made on 112 nights since March, 1899, 
and from the results the period was found to be 15-77594 
days. The maximum magnitude of this object is about 
12-0, and it varies through about two magnitudes. 
CaTaLoGuE OF DousLe Stars.—Prof. Doberck continues 
the results of his double-star observations at the Hong 
of the Astronomische 
Nachrichten. The present list is similar in form to those 
previously published, and contains the results for about 
170 Stars. 
THE TENTH INTERNATIONAL GEOLOGICAL 
CONGRESS. 
HE tenth International Geological Congress met this. 
year in Mexico, and the proceedings connected with 
it extended altogether over a period of nearly two months. 
Elaborate arrangements for the reception and entertain- 
ment of the members were made by the Mexican authori- 
ties; the President of the Republic, General Porfirio Diaz, 
himself manifested a lively interest in the work of the 
congress, and desired that everything possible should be 
done to make it successful. Over and above this, liberal 
financial assistance was rendered, the Mexican Government 
bearing half the cost of the steamer and railway fares of 
those attending the meeting. 
In all, more than six hundred membership tickets were 
issued; members resident in Mexico of course predomin- 
ated, and second place was taken by those from the re- 
mainder of the North American continent; of European 
countries, Germany was most strongly represented, which 
was perhaps natural in view of the large number of 
Germans who are engaged on the Mexican Geological 
Survey. It was surprising to find so few British repre- 
sentatives present, considering the great attractions which 
the country offers both to the geologist and to the 
mineralogist; all told, there were not more than five 
members who could reasonably be said to be representative 
of British science, and not one of these was officially 
delegated to the congress. This apparent indifference did 
not pass without comment on the part of the Mexicar 
officials. 
Several fairly long excursions, which will be referred 
to later, were arranged to take place before the meet~ 
ings, but the formal proceedings of the congress began 
with the meeting of the council on the morning of Thurs- 
day, September 6, when the general arrangements were 
finally settled, and a programme of papers, &c., was drawn 
up for approval at the opening session; this took place the 
same forenoon in the hall of the old Minerfa (now part 
of the National School of Engineering). This meeting 
was presided over by President Diaz, who also, at the 
conclusion of the business, formally declared the congress: 
open. In addition to the speeches of welcome, and 
addresses by the retiring president and the president-elect, 
the only business consisted in the approval of the proposed 
programme and of the proposed executive committee. The: 
principal offices in the executive were filled by the elec- 
tion of the corresponding officers of the provisional com- 
mittee in Mexico, as follows :—president, José G. Aguilera, 
director of the National Geological Institute (the Geological 
Survey); general secretary, Ezequiel Ordonez; and 
treasurer, Juan D. Villarello, both of whom are also om 
the Survey. 
The first of the ordinary meetings (which were held in 
the newly-completed National Geological Institute) took 
place on the afternoon of Thursday, September 6, under 
the presidency of Prof. Credner (Leipzig). A letter was 
first read from Mr. Karpinski (St. Petersburg), accompany- 
ing a copy of his memoir on ‘‘ Les Trochilisques ’’— 
doubtful fossils occurring only in the Devonian—after 
which Mr. G. H. Heilprin read a communication on 
““The Occurrence and Interrelation of Volcanic and 
Seismic Phenomena,’’ in which he maintained the view 
that shocks of tectonic origin are scarcely to be dis— 
