JuLy 17, 1902] 
dome-shaped hood, which is fixed a little above the arc 
itself. A rather long arc is burnt, and the effect is very 
similar to that produced by the Bremer lamp, only the 
light is of a slightly different colour. This lamp is also 
said to be three times as efficient as an ordinary arc. 
We have not space at our disposal to describe the ex- 
hibits fully. There is one other, however, which deserves 
special comment on account of its ingeniousness and 
possibly great importance. This is the Partridge 
““Sparklet” fuse, exhibited by Messrs. Elliott Brothers. 
This fuse is designed more especially for high-tension 
circuits carrying heavy currents. When the fuse in such 
a circuit goes an arc forms, and in order to prevent this 
burning, either a very long fuse or some form of oil fuse 
is used. In Mr. Partridge’s “Sparklet” fuse a short 
length only is used, and the terminals of the fuse wire 
are connected to an ordinary sparklet such as is now 
a familiar article for making soda-water. The arc when 
it forms burns between the two sparklets, and in a very 
few seconds one or other of these is burnt through ; the 
carbon dioxide immediately rushes out through the hole 
and blows out the arc. It will readily be understood that 
the more current the circuit is carrying, and the more 
power there is in the arc, the sooner will the sparklet 
burn through, and also the hole being larger the more 
certain it will be in its action. At the Agricultural Hall 
a model fuse was shown working a circuit of 2500 volts. 
The current was small, only about 6 amperes, the power 
being therefore about 15 kilowatts ; yet the arc was blown 
out in less than three seconds. Two sparklets are used, 
oneat each end of the fuse, in case one should be defective ; 
but this precaution has never been found necessary during 
all the experiments and trials that have been carried out. 
For the past eighteen months the apparatus has been in 
practical use, and has proved, it is said, thoroughly satis- 
factory. Mr. Partridge is certainly to be congratulated 
on a very ingenious idea ; it remains to be seen whether 
it will prove a sufficient cure for all the troubles that are 
likely to be met with now that large-power high-tension 
circuits are becoming common. M. S. 
THE ASTROGRAPHIC CHART. 
je is probably well known, even to those who are not 
astronomers, that an astronomical enterprise of con- 
siderable magnitude was initiated fifteen years ago, and 
is steadily, although somewhat slowly, progressing to- 
wards completion. In the year 1887 a conference of 
astronomers met at Paris to consider the best means of 
cooperating to make a complete map of the heavens on a 
large scale, and with all possible attention to accuracy, 
by photography. As the outcome of this conference, 
eighteen observatories of various nationalities undertook 
the work, the whole sky being divided up into eighteen 
zones ; a zone assigned to each observatory with due 
regard to its geographical position. A standard pattern 
of photographic telescope was chosen, and all the eighteen 
observatories obtained instruments of the required type 
and set to work. The enterprise being in several respects 
entirely new, it has been necessary to guide the procedure 
in the light of experience acquired; and conferences 
assembled at Paris in the years 1889, 1891, 1896 and 
1900 to report progress and compare notes. At the last 
of these conferences a second enterprise was undertaken. 
The small planet Eros, discovered in 1898, was to make 
a particularly close approach to the earth in the winter of 
1900-1, thus affording an opportunity, the like of which 
would not recur for thirty years, of determining the solar 
parallax ; it was felt that, although the main object of 
the association of observatories (viz. the formation of 
the Astrographic Chart) was not yet attained, still the 
advantages to astronomy which would result from utilising 
this exceptional opportunity were too great to be neg- 
NO. 1707, VOL. 66] 
NATURE 
273 
lected, and it was resolved that the cooperating obser- 
vatories should add to their programme the photographic 
observation of the little planet during the months October 
1900 to February or March 1gor. In connection with 
this second enterprise it has been found necessary to 
circulate a large amount of statistical material, such as 
approximate positions of the planet on different dates 
and of all the well-known stars lying near his path in the 
heavens, lists of the observations made at the different 
observatories, so that one might know how to match 
plates with another, and so on. The energy of the 
director of the Paris Observatory (who has from the first 
acted as director of the whole work) in printing and 
circulating this material has been most noteworthy. We 
have recently received the wmf circular relating to Eros, 
which is itself a pamphlet of 200 pages quarto, and re- 
presents a vast amount of work. In the first place, 
M. Loewy discusses, in two long memoirs (supple- 
menting a former one already published), what accuracy 
is obtainable from measures of photographic plates and 
what precautions are necessary to obtain that accuracy. 
The discussion is concerned with a number of minute 
details, and involves the adjustment of conflicting ad- 
vantages, so that there is room for difference of opinion 
in the conclusions ; but there can be but one opinion of 
the value of the material patiently collected and tabulated 
by M. Loewy, which can be examined in the light of any 
hypothesis preferred. The second part of the ninth 
circular gives, among other useful information, ephemer- 
ides of the planet Eros and of the sun, calculated to 
eight significant figures for every six hours—almost a 
new departure in such work, the only precedent being 
afforded by the investigations of Sir David Gill on the 
planets Victoria, Iris and Sappho, whereby he clearly 
showed that eight figures were necessary to represent 
the accuracy of heliometer measures. To advance one 
decimal place is of course a step of the gravest import- 
ance, and to Mr. Hinks, of the Cambridge Observatory, 
belongs the credit of being the first to show that an 
accuracy can be obtained from photographic measures 
of the Eros plates of the same order as that which led 
Sir David Gill to ask for an eight-figure ephemeris. 
The appearance of so much important literature in 
connection with this second enterprise, the photographic 
observation of the planet Eros, naturally suggests a 
glance at the state of affairs with regard to the main 
work, the Astrographic Chart itself. It is, as remarked 
in the first sentence of this article, some fifteen years 
since the work was initiated, and it should by this time 
be possible to form an estimate of the probable outcome 
and the approximate date of completion. It must be 
confessed that the original estimate of the time required 
has already been seriously exceeded. In the letter which 
summoned the conference of 1887 it is stated that :— 
“Ce grand travail . . . pourrait étre facilement exécuté 
en quelques années si dix ou douze observatoires bien 
répartis sur le globe pouvaient se partager convenable- 
ment la tache.” 
The phrase “quelques années” is somewhat indefinite, 
but it may be assumed that those who assembled in 1887 
would have been shocked to learn that after a lapse of a 
dozen years scarcely one-fifth of the work projected had 
been accomplished. Indeed, many who are tolerably 
familiar with the general course of events may be startled 
to hear this statement made ; and yet a glanceat the last 
comprehensive report available (see R.A.S. Monthly 
Notices, vol. |xi. p. 280) shows it to be only too true. 
It was decided to work on such a scale that 11,000 plates 
would be required to cover the sky, and this number was 
to be repeated four times, twice with short exposures (of 
6 minutes, 3 minutes and 20 seconds), and twice with 
long exposures (40 minutes). The plates of the first series 
(catalogue plates) were to be measured, and the measures 
printed and published; those of the second series 
