JUNE 12, 1902 | 
NATURE 
161 
electrical data certain conclusions have been drawn which are 
no doubt of considerable importance for the chemistry of steel 
and iron. 
Messrs. LONGMANS, GREEN AND Co. have just published 
new editions of two well-known works of science —Ganot’s 
“Physics” and Schiafer’s ‘‘ Essentials of Histology.’ Dr. 
Atkinson’s translation of Ganot’s ‘‘ Eléments de Physique ” has 
long been accepted as a standard description of the groundwork 
of physical science, and the sixteenth edition, edited by Prof. 
A. W. Reinold, F.R.S., will increase the high reputation the 
book has gained. Though physical science, even in its most 
elementary stages, needs to be studied practically to be of any 
value, the results obtained in the laboratory can only be fully 
understood by considering them in relation to the investigations 
of makers of scientific history. The best instruction in physics 
is that which combines a course of practical work with such 
exact and philosophical descriptions as are found in Ganot’s 
book, Practice without knowledge of theory is as bad as theory 
without practice. Prof. Reinold hasadded new matter, as well as 
revised the book, with the result that a comprehensive view 
is given of fundamental physical principles and relationships as 
now understood, suitable for elementary students of the science. 
The sections on magnetism and electricity have been greatly 
altered, and accounts of apparatus and machines which have 
ceased to be of interest have been omitted. Prof. E. A. Schifer’s 
“Essentials of Histology, Descriptive and Practical, for the Use 
of Students ” has reached its sixth edition. The work has been 
greatly enlarged, the chief additions being in the text relating 
to the structure of the central nervous system. Many new 
illustrations have also been added. The volume is both an 
elementary text-book of histology and a practical manual giving 
students precise directions for the microscopical examination of 
the tissues. 
THE additions to the Zoological Society’s Gardens during the 
past week include two Cape Zorillas (Zcfonyx zorz/la) from 
South Africa, presented by Capt. W. B. White ; a Red-footed 
Ground Squirrel (Xerus evythropus) from West Africa, pre- 
sented by Mr. P. G. Knight; a Ruddy Finch (Carfodacus 
erythrinus) from Siberia, presented by Mrs. G. A. Way ; two 
Mountain Ka-Kas (estoy notabilis) from New Zealand, pre- 
sented by Dr. W. H. Hornibrook; two European Pond 
Tortoises (Zmys orbicu/aris), European, presented by Mr. E. C. 
Brown; two and three Moloch Lizards (Moloch horridus) 
from Australia, presented respectively by Mr. F. Richards 
and Mr. W. Nichols; a Common Viper (Vifera berus), 
British, presented by Mr. E. Ball; two Striated Babblers 
(Aryga earliz), a Roofed Terrapin ( Kachuga tectum) from India, 
two Blyth’s Nicobar Parrakeets (Pa/aeornis caniceps) from the 
Nicobar Islands, two Black Iguanas (Metopoceros cornutus) 
from the West Indies, a Royal Python (Python regius) from 
West Africa, a Corn Snake (Coluber guttatus) from North 
America, deposited ; a Banksian Cockatoo (Calyptorhynchus 
banksiz) from New South Wales, purchased; a Thar 
(Hemitragus jemlaica) born in the Gardens, 
THE ROYAL OBSERVATORY VISITATION. 
ON Saturday last the Board of Visitors made their annual 
visit to Greenwich, and the Astronomer Royal submitted 
his report for the past twelve months. 
It cannot be said, however, that the weather was all that 
could be desired for such an occasion and for this time of the 
year. 
The following is a brief részmé of the report :— 
Transit-Circle. 
With this instrument the usual observations have been made, 
the undermentioned table giving the details of the number 
involved, 
NO. 1702, VOL. 66] 
Transits, the separate limbs being counted as 
one observation Ae ne 11,133 
Determinations of collimation error ... 303 
Determinations of level error ... 663 
Circle observations... vs a 3 9,666 
Determinations of nadir point (included in the 
number of circle observations) ote xh 681 
Reflection observations of stars (similarly in- 
cluded) : 505 
The number of stars observed in 1901 was 4.327. 
Good progress seems to have been made in the observations 
of the reference stars for the astrographic plates, for which 
10,000 stars are to be observed three times above and twice 
below pole—with the exception of about 1000 stars fainter than 
the ninth magnitude which cannot be observed below pole. A 
table giving the details of the progress up to date shows that for 
each of the five degrees of N.P.D. reckoning from the pole, 
100, 90, 46, 46, and 45 per cent. respectively of the necessary 
observations have been secured. 
The change in the method of adopting the azimuth error in- 
troduced at the beginning of 1900 has effected a satisfactory 
diminution of the small discordance in right ascensions taken on 
opposite sides of the pole. 
The colatitude of the transit-circle as found from observations 
of about 581 stars in 1901 is 38° 31’ 21°76, differing by —0”"14 
from the adopted value. The values of this correction since 
1897 are— 
1897 -o'17 | 1900 —o'1o 
1895 —O'15 1901 -O'14 
1899 —O'14 
Very satisfactory progress has been made with the re- 
reduction of Groombridge’s observations, the three years 1809, 
1810 and 1811 with 10,500 observations of R A. and N.P.D. 
having been finished since the last report. A catalogue of the 
positions of the stars in the Berdénexr Jahrbuch derived from 
Groombridge’s observations from 1806-1810 was forwarded to 
Dr. Auwers for use in the preparation of his fundamental 
catalogue, and he found that a large increase in accuracy had 
been effected by the re-reduction. 
The Altazimuth, 
Through the frequent breaking of the spider lines in this 
instrument, the micrometer slides have been altered to reduce 
the span, and the result has been very satisfactory. The instru- 
ment has been used in the meridian in four positions as a 
reversible transit-circle for observations of sun, moon, planets, 
and fundamental stars, and also for observation of the Eros 
reference stars, and reference stars for Sir David Gill’s helio- 
meter observations of major planets. The total number of 
observations made was 6556. 
Further determinations of the division errors have been com- 
pleted, and these have been combined with the previous results 
and definitive corrections for division error deduced. 
The Reflex Zenith Tube. 
This instrument was, as is well known, originally designed by 
Sir G. B. Airy for the purpose of determining the constant of 
aberration by observations of y Draconis, which passes very 
near the zenith of Greenwich, but after many years of observa- 
tions it was found that the results for parallax of y Draconis 
and aberration were anomalous, and an attempt was made in the 
years 1852 to 1886 by a long series of transits over the wires to 
refer these discordances to temperature effects, but without 
success. The observations of zenith distance of y Draconis 
were, however, continued up to 1899, when they were dropped 
owing to the pressure of observations for the new Ten Year 
Catalogue. This instrument has, however, become of great 
importance, for Mr. Chandler has recently shown that the ap- 
parently anomalous results previously obtained are explained by 
the variation of latitude, and that this instrument is specially 
adapted to the determination of the amount of this variation. 
It has therefore in consequence been decided to resume the 
observations of y Draconis without delay, and to observe such 
other stars as passed near enough to the zenith and were 
sufficiently bright. By suitable modifications it has been found 
possible to increase the utility of the instrument, by which 
several other stars down to the seventh magnitude can be 
observed, 
