702 
equal to the velocity acquired by a heavy body in fall- 
ing vertically in vacuo, under the action of gravity, 
through half the mean depth of the water. 
is highly probable, that, notwithstanding the variable 
density of the atmosphere with altitude above the 
surface of the earth, the same formula is applicable 
to long gravity-waves propagated in it; viz., that the 
velocity of the wave is equal to that which a heavy 
body would acquire in falling vertically through half 
the height of a homogeneous atmosphere. 
It is likewise well known, that the illustrious 
Newton (Principia, book ii. prop. 49), neglecting the 
influence of the thermal changes incident to the 
propagation of aerial elastic waves, deduced a most 
remarkable but imperfect formula for the velocity of 
sound in air, making it equal to that which a heavy 
body would acquire in falling vertically through half 
the height of a homogeneous atmosphere whose 
weight or pressure measures its elasticity. 
It will be noticed that the velocity of sound by New- 
ton’s formula is precisely the same as that given by 
the hydrodynamical formula for long aerial gravity- 
waves. It is true, that, in consequence of the heat 
momentarily developed or absorbed during the con- 
densations and rarefactions of the air, the actual velo- 
ity of sound exceeds that computed by the Newtoni- 
an formula by about one-sixth (a correction of the 
formula supplied by Laplace); yet the approximation 
is sufficient to seemingly co-ordinate the velocities of 
these diverse kinds of aerial waves. 
Thus, the height of a homogeneous atmosphere, 
under standard conditions, being 7,990 metres, the 
velocity of sound computed by the Newtonian formula 
-equals 279.96 metres per second at 0° C., and 293.5 
metres per second at the August temperature of 27° C. 
The actual velocity of sound at above-indicated tem- 
peratures equals 332.5 and 348.6 metres per second 
respectively. 
On the other hand, the following are some of the 
estimates that have been made of the velocity of 
the Krakatoa atmospheric waves :— 
Velocity in me- 
tres per second. 
Gen. Strachey . in England. 301.3 to 315.0 
Professor Forster . at Berlin 278.0 
Mr. Renou : at Paris . 246.0 to 278.0 
Mr. Renou in France . ; 305.0 to 319.0 
Mr. Wolf. . atiRanis' e085. i fee 325.8 
Mr. Baillaud. at Toulouse 324.0 
Mr. Hall . at Jamaica. 308 5 
All of these estimates fall decidedly short (as theory 
indicates) of the actual velocity of sound in air; and 
most of them approximate somewhat more nearly to 
the velocity computed by the Newtonian formula, 
which, as we have seen, corresponds with the hydro- 
dynamical formula for long aerial gravity-waves. 
Considering the inherent difficulties of the precise 
determination of the several data requisite for deduc- 
ing the true velocity of the atmospheric waves origi- 
nating at Krakatoa on this occasion, we need not 
be astonished at the considerable divergence in the 
estimates, or that the assumed exact coincidence of 
velocities of the two kinds of aerial waves fails to be 
verified in an accurate manner, either by theory or by 
- observation. , JOHN LECONTE. 
Berkeley, Cal., May 15. 
A near view of Krakatoa in eruption. 
In connection with the remarkable atmospheric 
wave, which, starting from Krakatoa at the time of 
the eruption, ‘‘ travelled no less than three and a 
a9 ee 
SCIENCE. 
Now, it. 
“Se, oP) eee ae eee se 
[Vou IIL, No. 71. 
quarter times round the whole circumference of the 
earth,’ 1 the following extracts from the log of a 
vessel sailing in the close vicinity of Krakatoa may 
be of interest: — 
Extracts from log of barque William H. Besse, from 
Batavia towards Boston. 
Aug. 26. — This day commences with light airs and 
calms. Light airs throughout the day. At5.30P.M., 
wind hauling ahead, let go starboard anchor with 
thirty fathoms chain, clewed up and furled all sail. 
Adam light bore W. 1-48. and E. by 8. Throughout 
the afternoon and night, heard heavy reports, like the 
discharge of heavy artillery, sounding in the direc- 
tion of Java Island. Very dark and cloudy through- 
out the night, with continual flashes of lightning. 
Barometer 30.15. 
Aug. 27. Commences with strong breezes, and 
thick, cloudy weather. Barometer 30.12. At9.50 A.M., 
pilot left ship. Hove the lead every fifteen minutes. 
At daylight noticed a heavy bank to the westward, 
which continued to rise; and, the sun becoming ob- 
scured, it commenced to grow dark. The barometer 
fell suddenly to 29.50, and suddenly rose to 30.60. 
Called all hands, furled every thing securely, and let 
go the port anchor with all the chain in the locker. 
By this time the squall struck us with terrific force, 
and we let go starboard anchor with eighty fathoms 
chain. With the squall came a heavy shower of sand 
and ashes, and it had become by this time darker 
than the darkest night. The barometer continued to 
rise and fall an inch at a time. ‘The wind was blow- 
ing a hurricane, but the water kept verysmooth. A 
heavy rumbling, with reports like thunder, was heard 
continually; and the sky was lit up with fork light- 
ning running in all directions, while a strong smell 
of sulphur pervaded the air, making it difficult to 
breathe. Altogether, it formed one of the wildest 
and most awful scenes imaginable. 
The tide was setting strong to the westward through- 
out the gale, at the rate of ten knots per hour. At 
3 P.M. the sky commenced to grow lighter, although 
the ashes continued to fall. ‘The barometer rose to 
30.30, and dropped gradually to 30.14, when it became 
stationary. The whole ship, rigging and masts, were 
covered with sand and ashes to the depth of several 
inches. * 
Aug. 28. — Commences with light airs, and thick, 
smoky weather. Hove up starboard anchor, and 
hove short on port anchor. Dead calm throughout 
the day and night. Saw large quantities of trees and 
dead fishes floating by with the tide; the water having 
a whitish appearance, and covered with ashes. This 
day ends with a dead calm, and thick, smoky weather. 
Aug. 29.— This day commences with calms, and 
thick, smoky weather. Made all sail throughout the 
day. Moderate winds, and thick, smoky weather. 
Passed large quantities of driftwood, cocoanuts, and 
dead fishes. At 8 P.M., passed Anjier,? and could 
see no light in the lighthouse, and no signs of life on 
shore. Furled all light sails, and stood under easy 
sail throughout the night. Day ends with moderate 
winds and cloudy weather. Barometer 30.14. 
Aug. 80. —Commences with moderate winds and 
cloudy weather. At daylight made all sail with a 
fresh breeze from the westward. Found the water 
for miles filled with large trees and driftwood, it 
being almost impossible to steer clear of them. Also 
passed large numbers of dead bodies and fish. Kept 
a sharp lookout on the forecastle throughout the day. 
1 Nature, vol. xxx. p. 12. 
2 All except the foundation of the lighthouse was destroyed — 
by the tidal wave. 
