Fuly 16, 1885 | 
be so well plotted on this last survey that the amount of gorge 
excavated since 1750 should be knowable toan acre. The west 
fall, then, only slightly the larger, has ever since been widening, 
lowering its edge, and getting more of the stream; so that the 
east one, comparatively stationary, retaining its height and de- 
creasing in yolume, must dry up, and its bed and all the isles 
become part of New York State. E. L. GARBETT 
July 11 
Sky Glows 
EVER since the sunsets of 1883 and last year there has been 
at times an abnormal glare both before and after sundown. But 
I have seen nothing in the way of twilight effect so strange as 
that of Monday evening, the 6th, when about 10 p.m. a sea of 
luminous silvery white cloud lay above a belt of ordinary clear 
twilight sky, which was rather low in tone and colour. These 
clouds were wave-like in form, and evidently at a great eleva- 
tion, and though they must have received their light from the 
sun, it was not easy to think so, as upon the dark sky they 
looked brighter and paler than clouds under a full moon. A 
friend who was with me aptly compared the light on these 
clouds to that which shines from white phosphor paint. This 
effect lasted for some time after 10 p.m., and extended from west 
to north, the lower edge of the clouds, which was sharply defined, 
was about 12° above the horizon. Rost. C. LESLIE 
6, Moira Place, Southampton, July 8 
Black and White 
My daughter has two terriers, one black, the other white ; she 
has noticed that in the dusk of the evening the black dog is 
much more visible than the white one, and has asked me the 
reason for this fact. I cannot properly explain why a white or 
light coloured garment shows much less in the dusk than a dark 
coloured dress, but this is a well-known fact to all sportsmen 
who shoot ducks at night, when it is their custom to wear a 
night shirt or other white dress over their ordinary costume. 
When the black and white dogs are playing together in the dusk 
of evening, the black dog can be distinctly seen when the white 
dog, at the same distance, is quite invisible. Will you please 
explain this ? Wo. E. WARRAND 
Bught, Inverness, July 8 
“Foul Water” 
DurRInG a brief stay at Beaumaris in June 1883, and again in 
June 1884, I had frequent opportunities of observing the ‘‘ ge- 
latinous masses” mentioned by Mr. Shrubsole as occurring in 
large numbers at Sheerness-on-Sea. I first noticed them in 
1883, while procuring a supply of water for my marine tanks at 
home. They then existed in very large numbers, and as I had 
no means of filtering the water before returning to Manchester, 
I almost expected to find it ‘‘foul” upon my arrival. I was, 
however, agreeably disappointed. The ‘‘ gelatinous masses” 
had settled at the bottom of the jars, and were apparently dead. 
While at Beaumaris I subjected a few specimens to microscopical 
examination, but being busy with other work did not learn more 
than is given in Mr. Shrubsole’s description. 
Manchester HERBERT C. CHADWICK 
Earthquake-Proof Buildings 
UNLESS my memory plays me very false a number of light- 
houses secured against earthquake shocks by saucers and balls 
were built in Japan just about twenty years ago from the designs 
of Mr. Stevenson of Edinburgh. Won. Muir 
The London Institution, Finsbury Circus, E.C. 
THE QUESTION OF CIVIL AND 
ASTRONOMICAL TIME 
= of the points made at the Washington Congress 
was that if Universal Time (surely Earth-Time or 
Prime Meridian Time would be a better term) were 
generally accepted, astronomical time might be abol- 
ished, astronomers accepting the new day of twenty-four | 
hours commencing at midnight. 
Since the Congress the question naturally has been 
NATURE 
245 
well considered, and we think it desirable that we should 
now refer to some of the most important opinions which 
have already been given, not only as regards the desira- 
bility of the change, but as to the time at which that 
change should be brought about. 
Among the first to accept the resolution was the 
Astronomer- Royal, for theinternal use of the Observatory 
of Greenwich. Many opinions were collected at an early 
date and forwarded by Mr. Chandler, the Secretary of the 
U.S. Navy to the Senate. This action grew out of an 
order of Commodore Franklin, the Superintendent of the 
U.S. Naval Observatory, to adopt the new time on 
January 1, 1885; this was communicated to Prof. 
Newcomb, the Superintendent of the American Nautical 
Almanac, and drew a reply from Prof. Newcomb, from 
which we make the following extract :— 
“*(r) The Conference expresses the hope that as soon as may 
be practical the astronomical and nautical days will be arranged 
everywhere to begin at mean midnight. 
**(2) That east longitudes shall be counted as plus and west 
longitudes as minus. 
“The first of these recommendations proposes a change in 
the method of counting astronomical time which has come down 
to us from antiquity, and which is now universal among astro- 
nomers. The practice of taking noon as the moment from 
which the hours were to be counted originated with Ptolemy. 
This practice is not, as some distinguished members of the 
Conference seem to have supposed, based solely upon the in- 
convenience to the astronomer of changing his day at midnight, 
but was adopted because it was the most natural method of 
measuring solar time. At any one place solar time is measured 
by the motion of the sun, and is expressed by the sun’s hour 
angle. By uniform custom hour angles are reckoned from the 
meridian of the place, and thus by a natural process the solar 
day is counted from the moment at which the sun passes over 
the meridian of the place or over the standard meridian. For the 
same reason sidereal time is counted from the moment at which 
the vernal equinox passes over the meridian of the place, and 
thus the two times correspond to the relation between the sun 
and the equinox. 
‘It would appear that the Conference adopted the recom- 
mendation under the impression that the change would involve 
nothing more than the current method of reckoning time among 
astronomers, and could therefore be made without serious in- 
convenience. A more mature consideration than time permitted 
the Conference to devote to the subject would, I am persuaded, 
have led that distinguished body to a different conclusion. 
‘4 change in the system of reckoning astronomical time is 
not merely a change of habit, such as a new method of counting 
time in civil life would be, but a change in the whole literature 
and teaching of the subject. The existing system permeates all 
the volumes of ephemerides and observations which fill the 
library of the astronomer. _ All his text-books, all his teachings, 
his tables, his formule, and his habits of calculation are based 
on this system. To change the system will involve a change in 
many of the precepts and methods laid down in his text-books. 
“But this would only be the beginning of the confusion. 
Astronomical observations and ephemerides are made and printed 
not only for the present time, but for future generations and for 
future centuries. If the system is changed as proposed the 
astronomers of future generations who refer to these publications 
must bear the change in mind in order not to misinterpret the 
data before them. The case will be yet worse if the change is not 
made by all the ephemerides and astronomers at the same time 
epoch. It will then be necessary for the astronomers of the 
twentieth century, using ephemerides and observations of the 
present, to know, remember, and have constantly in mind a 
certain date different in each case at which the change was 
made. For example, if, as is officially announced, the Naval 
Observatory introduces the new system on January 1, 1885, then 
there will be for several years a lack of correspondence between 
the system of that establishment and the system of the American 
Ephemeris, which is prepared four years in advance. 
“Tt is difficult to present to others than astronomers who have 
made use of published observations the confusion, embarrass- 
ments, and mistakes that will arise to their successors from the 
change. The case can be illustrated perhaps by saying that it 
is of the same kind as—though in less degree than—the con- 
fusion that would arise to readers and historians in the future if 
