i 
FEsRUARY 4, 1897 | 
NATURE 
329 
OUR ASTRONOMICAL COLUMN. 
TABLES FOR FINDING LATITUDE VaRIATIONS.—Prof. S. C. 
Chandler gives, in the Astronomical Fournal (No. 392), tables 
for finding the variations of latitude for the present year, these 
being a continuation of those published in an earlier number of 
the same journal (No. 193). The formulz used in the computa- 
tion were derived entirely from observations made previous to 
1894"0, so that, as is suggested, a good opportunity is given of 
comparing the theoretical with the observational places obtained 
since that date. Such a comparison made by him shows that 
only an average difference without regard to sign of +0"'041 is 
indicated, a quantity sensibly not greater than the uncertainty of 
the observed points themselves. This satisfactory conclusion 
shows us then that predictions of the movements of the pole 
may, with no reasonable doubt, be made for several years be- 
forehand. From an investigation, which Prof. Chandler has in 
hand, he informs us that a discussion of the whole series of ob- 
servations from 1889 to 18965, demonstrates that the radius of 
the 428-day revolution has been diminishing in accordance with 
the law given by him (Equation 52, Astr. Yourn., 322), but at a 
slightly greater rate. He further adds that a comparison of the 
observations at Kasan in 1895 and 1896, in conjunction with 
those made in Central Europe, confirms the fact of the ‘* remark- 
able eccentricity of the annual ellipse which was developed from 
the previous European and American observations.” 
Tue Tririp NesuLa.—Prof. Pickering, in the Harvard 
College Observatory Circular (No. 15), gives a brief account of 
the performance of the Bruce photographic telescope which is 
now erected at Arequipa. This instrument was generously 
given by Miss Catherine Bruce, as it had been suggested that 
a telescope of 60 cm. aperture and 343°8 cm. focal length 
would give most probably excellent photographic results. Since 
it was set up, it has been in constant use by Prof. Bailey, and 
a plate accompanies the Circular to serve to illustrate the work 
already accomplished. The original negative was taken last 
year, on June I1, with an exposure of three hours, on a plate 
14x17 in. The region covered extends in R.A. from 17h. 4om. 
to 18h. 10m., and in declination from —20°8° to —26'5°. The 
two nebulz on that part shown in the figure are the Trifid 
Nebula N.G.C. 6514 and N.G.C. 6523. It is stated that 
photogravures of two regions have been prepared, and a limited 
distribution, mainly to observatories, is being made of them. 
It is also proposed to issue maps of other portions of the sky, 
such as the Magellanic Clouds. It was originally intended to 
map the entire sky, but it is now thought better to furnish 
contact prints on glass from the original negatives to such 
astronomers as will make use of them. 
Excellent results have already been obtained with objective 
prisms, and these, as we are informed, will be communicated in 
a future Circular. 
THE PERIOD OF SIRIUS’ CoMPANION.—In this column for 
November 19, we gave the measures made by Prof. Aitken of 
the companion of Sirius, and pointed out that the position 
angle differed from that reported by Dr. See. In the current 
number of the 4st. Mach. (No. 3400), Herr H. J. Zwiers com- 
municates a short note, in which .he has taken the mean of the 
new measures made at the Lick Observatory—namely : 
1896°8235 ... Position angle 189°28° ... Probable error + 0°67" 
Distance Bayaiks.: op EeTSLOLE2- 
and compares this place with that given by the computation of 
the orbit (4s¢v. Nach., 3336), which is 
Postion angle 185°99° 
Distance 4°05" 
The difference, observation minus calculation, gives for the two 
measures: position angle + 3°29° and distance —0°31", show- 
ing that the computed place is sufficiently near until more ob- 
servations have been obtained. Prof. Auwer’s suggestion that 
the period may be a little longer than 49°4 years is thus en- 
dorsed, while Herr Zwiers’ period of 51°10 years gives a some- 
what too slow a movement. 
Hear Rays OF GREAT WAVE-LENGTH.—It is well known 
that the spectrum we see when observing an ordinary red-hot 
poker through a prism is only a fractional part of a much more 
extensive one. In addition to the common light waves there 
are several other kinds, such as electrical, heat, &c., all of which 
may form part of the spectrum in its entirety, and the attempt 
has often been made to increase our knowledge over the broad 
NO. 1423, VOL. 55] 
region between the electrical and light waves. This may be 
done by either reducing the wave-lengths of electrical oscilla- 
tions, or by the discovery and measurement of longer heat 
waves. In the pamphlet we have before us, a reprint from the 
Physical Review (vol. iv. No. 22), Messrs. H. Rubens and 
E. F. Nichols have just completed a very interesting investi- 
gation of the infra-red waves of great wave-length. The new 
theories of dispersion have suggested a method by means of 
which homogeneous rays of great wave-length may be obtained, 
and in sufficient quantity to make the determination of their 
properties and wave-length possible: this can be done, further, 
without the intervention of either a prism or grating. The 
authors make “ reflection” the basis of their investigation, and 
in the instrument they devised they have chosen three reflectors 
of the same substance as the light source used. The bolometer 
employed was one of platinum, after the design of Lummer and 
Kurlbaum, the absorbing layer being a coating of platinum 
black, deposited electrically. 
The two substances studied were quartz and fluorite. In the 
case of the former, the mean wave-length of the observed rays 
gavein the firstand third orders 0°00887 mm. and 0:00882 mm. 
respectively. The agreement between the two values lies well 
within the limit of probable error. For fluorite the maximum 
energy in the diffraction spectrum of the first order corresponded 
to a wave-length of 0'0244 mm., the mean from other series 
varying from 0°024 mm. to 0’025 mm. 
The authors remark that if these values be compared with 
those computed from the Kettler-Helmholtz dispersion formula 
for the middle of the absorption bands, in each case the ob- 
served value for quartz is 10 per cent., and for fluorite 20 per 
cent. less than the computed. As inaccuracies may arise from 
the computed values, and there may be errors in the experi- 
mental values, such as, for instance, a variation in the absorption 
of platinum black with the wave-length, yet ‘‘ one is justified 
in regarding the agreement between the observed and computed 
wave-lengths as close enough to confirm the utility of the 
theories involved.” 
The rays corresponding to the infra-red absorption band in 
fluorite lie thus almost exactly midway between the shortest 
ultra-violet rays of Schumann (A = 00001 mm.) and the 6 mm. 
electrical waves of Lebeden, reckoning the interval according 
to octaves, as is customary in acoustics. 
The authors hope, moreover, to be able to refine the present 
method of observation, and study waves of greater wave-length ; 
and, by means of an improved radiometer, obtain a much higher 
degree of sensitiveness. 
THE VALUE OF PATHOLOGICAL 
RESEARCH.1 
ON the occasion of the jubilee of Queen’s College, Belfast, 
last month, the new physiological and pathological 
laboratories were formally opened by the Lord Lieutenant. On 
the following day an address of welcome and congratulation 
was presented by the North of Ireland Branch of the British 
Medical Association and the Ulster Medical Society to Lord 
Lister, who, after receiving it, spoke as follows :-— 
It gave me very great pleasure to witness the opening of the 
physiological and pathological laboratories yesterday by His 
Excellency the Lord Lieutenant. Such an establishment is 
calculated to be of enormous advantage to the North of Ireland. 
The benefits which it will confer will be of various kinds. In 
the first place it will be of very great assistance to the medical 
practitioner in forming his diagnosis of the disease of the 
patient he has to treat. In these days the knowledge of 
pathology has made immense advances ; and, at the same time, 
along with those advances in pathological knowledge, there has 
arisen increased complexity in the methods of examining patho- 
logical objects. Section cutting, staining, microscopic examina- 
tion—these are matters of the utmost moment ; and yet for the 
general practitioner there may be neither the apparatus nor the 
time requisite for that kind of investigation. It will, therefore, 
be of great advantage to the practitioner, when he has removed 
or in any way obtained a portion of a morbid growth, to send 
it to a central institution, and have absolutely definite informa- 
1 An address delivered January 20, in connection with the opening of the 
new physiological and pathological laboratories in Queen's College, Belfast, 
during the celebration of the jubilee of the College, by Lord Lister, P-R 5S. 
