8 NATURE 
“nomes,” but also for more than one temple, or 
important shrine, and its attendant city in many 
of the “‘nomes.” 
The event which induces M. Daressy to publish 
the fruits of his erudition upon this subject is the 
publication by him of a bronze zodiac with a 
series of two rows of twelve figures, the outer 
zone being the familiar zodiacal signs, and the 
inner, twelve animal symbols, attributable, 
Egyptologists think, to the twelve forms or phases 
assigned to the sun during his twelve hours’ 
journey. These, in the earthly Egyptian 
gazetteer, are assigned to twelve of the twenty 
districts of Lower Egypt. This newly found double 
zodiac is very valuable for the explanation it 
affords of the symbols of the constellations upon 
the Denderah zodiac, because all these figures are 
intermingled in the large central circular disc, 
mixed up with deity figures representing the 
planets and certain prominent high-magnitude 
stars and the decans. 
It should be stated that the zodiacs designed, 
and hitherto found, in Egypt are not of great 
antiquity, The arrangement of their symbols and 
of figurative objects for some constellations has 
certainly been produced under Greek influence. 
They appear to emanate from the Egyptian priests 
uniting their old stellar figure mythologies to the 
astronomical astrology of the Alexandrian school. 
Both parties, however, must at the date of the 
composition of these zodiacs havesbeen acquainted 
with the Chaldean science of the heavens, deriva- 
tions from which appear in the Old Testament 
and early Greek classics and art. 
The deity symbols upon the Babylonian 
boundary stones are almost always astral and 
frequently zodiacal. Since the large increase in 
number of these monuments found at Susa, we 
have a much more complete series of the symbols. 
Thus upon the stele of Melishipak we have the 
figure of an archer with the upper part human 
and the lower part that of a double-headed horse 
and two tails; those of a horse and a scorpion; 
also wings. This representation agrees almost 
completely with the Sagittarius of the Denderah 
zodiac, and with this Sagittarius the scorpion is 
associated in both cases. 
This assimilation of Mesopotamian astronomy 
is identical with the adoption by the Egyptians of 
several Babylonian legends of the gods _ into 
Egyptian mythology. These exploits were foisted 
upon the deeds of Egyptian deities. For ex- 
ample, the Izdubar (Hercules) legends were in 
some Cases introduced into the conflicts of Horus. 
The parallels between terrestrial Egyptian geo- 
graphy and the places of the stars must, however, 
» have been very old in Egypt, though not anterior 
to the era of Menes. M. Daressy ingeniously 
explains the principles upon which these were 
arranged, and henceforth Egyptologists will trace 
in the primitive texts allusions to them and decide 
approximately when they were invented. The 
favourite constellations other than the zodiac were 
the circumpolar stars, because they never set and 
so were symbolic of eternity. ; 
NO? 2445, VOL. 98] 
[SEPTEMBER 7, 1916 
In addition to the famous. zodiac from Denderah, | 
now in the Louvre, we have, among others, the 
new one at Cairo, the planisphere and tableaux 
carved on the hypostyle hall at Denderah, copies 
of others once at Esneh and Erment, and the coffin. 
of Hern-netch-tep in the BritiSh Museum. 
JOSEPH OFFORD. 
THE PREVENTION OF COLLISION AT 
SEA? 
pect . JOLY proposes, in the work before us, 
that sound, which travels at different rates 
through different fluids, should be utilised for 
navigational purposes as well as for the preven- 
tion of collision. The rate of travel of sound 
through air—viz. 1090 ft. per sec. at a tempera- 
ture of 32° F. (zero C.), or 1100 ft. per sec. at a 
temperature of 52° F. (1171 C.)—has 
been utilised in H.M. naval surveying  ser- 
vice for measuring bases in _ places 
it is not possible to land, owing 
coast being covered 
to the 
has a plug driven in its muzzle and to note the 
time which elapses between the flash of the dis- 
charge and the report of the mortar. For this 
purpose a chronometer watch which beats five — 
times for every two seconds of time is used, and 
it will be evident that each beat of the watch 
represents 440 ft., so that if the observer makes 
a mistake in counting the beats a corresponding 
error will be the result in the length of the base. 
This method of ascertaining distance has also 
been used to ascertain the distance off a cliffy 
coast when sailing along it. In H.M.S. Actg@on, 
when sailing along the coast of Russian Tartary, 
which has very few distinctive marks, a gun was 
fired at intervals and the beats of the watch 
counted until the echo was heard. Half the time 
elapsed gave the distance off. 
In the case of sound travelling through water 
the rate is much more rapid, and that rate depends 
on temperature as well as on the density. In 
river water the rate is 4714 ft. per sec. at a tem- 
perature of 55° F. (13° C.), and of s5o13 ft. per 
sec. at a temperature of 86° F. (30° C.), whilst 
in sea-water, at a temperature of 68° F. (20° C.), 
its rate is 4761 ft. per sec., but where the specific 
gravity of the water is increased, as in the Medi- 
terranean or Red Sea, the time will be different. 
In thick weather, therefore, when the flash of a 
gun cannot be seen, the distance off can be ascer- 
tained by noting the number of beats between 
the receipt of a sound travelling through water 
and one through the air, provided they are 
emitted simultaneously. This’ difference is 
4°25 secs. for each nautical mile the observer is 
distant from the point where the sound is emitted, 
or 10°63 beats of the watch per mile. 
In a vessel fitted to send or receive radio- 
telegraphic messages, if a signal be sent simul- 
taneously with the sound signals it is equal to 
seeing the flash of the gun. If the number of 
1 “Synchronous Signalling in Navigation.” By Prof. J. Joly. Pp. 64. 
(tenders T. Fisher Unwin Lid., 1916.) Price 3s. 6¢. net. 
long 
where > 
with mangrove growth. 
The system in use is to fire a small mortar which 
