— 
Fuly 16, 1885 | 
Mr. HARRINGTON, Ann Arbor— 
Will do as Greenwich does. 
Prof. HOLDEN, Washburn Observatory— 
Begin in 1890. 
Prof. YOUNG, Princeton— 
Begin January 1, 1885. 
Mr. Swirt, Warner Observatory— 
Begin January 1, 1885. 
Prof. LANGLEY, Alleghany— 
Begin January 1, 1885. 
Mr. PORTER, Cincinnati— 
Begin January 1, 1885. 
Prof. PRITCHETT, Washington University Observatory— 
Wait a year at least for general concensus. 
Prof. PETERS, Clinton. We extract his letter :— 
““Thave, from the beginning, attached very little importance 
to the object and the proceedings of the International Meridian 
Conference. 
“The suggestions and recommendations which have been the 
result refer principally to things that are already in existence ; 
for example, the reckoning of geographical longitudes east and 
west from Greenwich is in practice with most nations. The 
proposition to count the hours of the day from o to 24 also in 
civil life will scarcely ever be adopted, for nobody (except per- 
haps sick people lying in bed) will have patience enough to 
count the striking of the clock up to 24, not to speak of the 
greater liability of miscounting the strokes and of the difficulty 
in reading off the turret dial if the circle be divided into twenty- 
four parts’ But what concerns astronomers directly is the 
change proposed by the Conference in the beginning of the 
astronomical day, in regard to the introduction of which you ask 
for my views. It is quite unimportant, of course, whether we 
begin from noon or from the preceding midnight; the reasons 
for taking the former as the starting-point exist no longer. Our 
clocks nowadays are not regulated, as in former times, by ob- 
serving the culmination of the sun, and with the telescopes of 
increased size observations are continued not during the night 
alone, but are carried on as well in day-time, so that a break in 
the date at midnight is hardy more grievous than one at noon. 
While thus we might readily conform with the proposal of the 
Conference, and put our clocks back by twelve hours, we ought 
to hesitate nevertheless very much to do so at once, especially 
for two reasons: First, a general agreement and understanding 
among astronomers (not of the United States alone but of all 
nations) should be had ; otherwise it would become necessary 
for avoiding confusion to add to every observation we publish 
some such words as ‘old-style time’ or ‘new-style time.’ The 
subject undoubtedly will be discussed in the astronomical 
periodicals, and in societies representing our science. If 
authorities such as the Royal Astronomical Society, the German 
Astronomical Gesellschaft, the larger active observatories, &c., 
agree in favour of the change, the system of reckoning the astro- 
nomical day from midnight will soon be adopted universally. 
But a partial proceeding seems highly objectionable. Second, 
if we make a change in the time-keepers of the Observatory 
now, the use of the astronomical ephemerides, as they lie com- 
puted before us, will be made in many respects heavy. Take, 
for example, the places of the fixed stars, which are given for 
upper culmination from ten to ten days. When the sidereal 
day begins before noon, its date in the new arrangement of the 
solar day is changed. And every star place that we wish to 
take out of the ephemeris, therefore, requires some additional at- 
tention and reflection astothe corresponding date. In the American 
Nautical Almanac, where the tenths of the solar day are given, 
this inconvenience, to be sure, is not so great ; we need only to 
diminish our argument by 0'5 day for having that of the table. 
A similar reduction of the argument must be made in using the 
lunar ephemeris, and of course in all the data expressed in solar 
time. In this way a source for at least possible mistakes is 
opened, and I think it therefore desirable that the change in the 
Nautical Almanacs should recede that in the observatories. The 
American as well as the British Nautical Almanacs are published 
as far as 1887, inclusive ; the next or the next two following 
years may be under preparation. 
“These considerations together lead me to the conclusion that 
NATURE 
- Ephemerides. 
247 
it seems 7of advisable to introduce the change in the beginning 
of the astronomical day defore the year 1890.” 
More recently two European astronomers have re- 
corded their opinions. Prof. Struve in a pamphlet,! and 
Prof. Oppolzer in the Monthly Notices. The former 
thus expresses his views :— 
“In regard to the change in the beginning of the astronomi- 
cal day, thinks that the question before astronomers is not only 
of giving up a long-established custom, with consequent changes 
of rules of many years’ standing, but it also involves a serious 
interruption of astronomical chronology. Without a doubt the 
astronomer would haye to make a decided sacrifice in conform- 
ing to the wish of the Conference; but, after all, this sacrifice 
is no greater than our forefathers made when they changed from 
the Julian to the Gregorian calendar—a sacrifice to conve- 
nience of which we are still made sensible whenever we have 
occasion to go back to early observations. 
““ We need have little hesitation in making a similar sacrifice 
if it will prevent discordance between the civil and scientific 
custom of reckoning time, particularly troublesome where astro- 
nomical establishments come in contact with the outer world. 
“* Prof. Struve states that the Pulkowa Observatory is prepared 
to adopt the new time, the only question being as to the epoch 
when the change should be introduced in the publications of the 
Observatory. He is inclined to recommend that this should be 
deferred until some agreement can be reached by astronomers, 
and until the new time is adopted in the Ephemerides. This 
might be for the year 1890, or perhaps, better still, at the 
beginning of the next century.” 
Prof. Oppolzer’s opinion is as follows :— 
“When once such a universal time is introduced for all 
purposes it is quite natural that the question must arise, 
if there is indeed so great a necessity to retain in astro- 
nomy, and only in astronomy, a different reckoning of time. 
I fail to see this necessity, and I do not think that it would 
cause any serious trouble or confusion if a change were to be 
made in our astronomical reckoning ; whilst a special mode of 
reckoning time in one science only, when all others use the 
generally-adopted standard, will, without doubt, be a source of 
error and confusion.’ He then takes up in some detail the 
objections urged against the proposed change by Prof. Newcomb, 
and he discusses the changes which would be necessary in the 
Prof. Oppolzer proposes to give practical effect 
to his views by adopting the new reckoning of time in an ex- 
tensive list of Sooo solar and 5200 lunar eclipses which he is 
now preparing for publication.” 
Science, in an article on this subject, concludes as 
follows :— 
“Tt is difficult to see how this matter will finally be decided. 
It is evidently a question for astronomers to settle among them- 
selyes ; but so far they seem to be very evenly divided. For 
instance : out of some twenty-seven astronomers whose opinions, 
more or less decided, have been accessible for a count, thirteen 
seem inclined to favour the proposed change, while fourteen are 
opposed to it. And among the fvos are Adams, Struve, and 
Christie ; among the cons, Newcomb, Foerster, and Auwers.” 
MR. FREDERICK SIEMENS’S GAS LAMP 
HE illuminating power of the most novel appliances 
for the production of light having, for economical 
reasons, been made more and more intense, and therefore 
more injurious to the eyesight, it follows that the eye must 
be protected as much as possible from the direct action 
of the light, with the least possible loss or diminution of 
effect. In other words, rooms should be lighted only by 
means of indirect rays or diffused light, the source of 
light itself not being directly visible. This is, in the 
author’s opinion, a consideration of the highest import- 
ance as regards artificial illumination, which has only as 
yet received partial attention. ‘ 
Until lately three main points only have been considered 
in any lighting application—viz. that the apparatus em- 
ployed should be simple both in its construction and in 
its use; that the light should be of sufficient intensity for 
t “Die Beschliisse der Washingtoner Meridianconferenz.” 
