‘without replenishing the supply. 
_ 
268 
NATURE 
| Fan. 1 9, 1882 
Beaumont Compressed Air Engine Company at Stratford 
with a separate engine, hauling an ordinary passenger car 
behind it are likely to bring the question prominently 
before the notice of tramway companies, and the hopeful 
remarks made before the last meeting of the British Asso- 
ciation by Sir Frederick Bramwell, with regard tothe use of 
compressed air, must have contributed towards the same 
result. The experience of the writer, who has been longer 
at work on the subject than either of the representatives 
of the systems referred to is, however, so much opposed 
to their proposals, that he does not feel himself to be an 
altogether unbiased critic of their proceedings. It is sin- 
cerely to be hoped, for the sake of suffering horseflesh, 
and in order to promote the expansion of intramural 
locomotion throughout the country, that a fair trial may 
soon be given to the rival systems, including electricity. 
This, however, is but a remote contingency if tramway 
companies continue to adhere to the principle, or rather 
no principle, that they have to get everything, and the 
men who add to their dividends nothing, for their pains. 
The writer’s car, which can be seen at work by any one 
interested, is entirely self-contained, and offers absolutely 
no obstructions to the convenience of passengers, and it 
carries forty of them a distance of more then seven miles 
with a low and safe pressure of air in the receivers, and 
The distance it would 
travel with the pressure used in Col. Beaumont’s engine is 
over twenty miles with one charge of air. The weight 
complete, including the fittings for passengers, is less than 
that of any compressed air tramway engine which the 
writer knows of, hauling a tramway car behind it. 
W. D. ScoTT MONCRIEFF 
SEA FROTH 
HAVE just read with interest Dr. Gladstone’s article 
in NATURE (vol. xxv. p. 33) on “*Sea Froth.” I 
venture to inclose, as an illustration of his nephew’s 
observations, portion of a description of such froth as wit- 
nessed by myself during a Mauritius hurricane, extracted 
from a book I am now publishing. It will be noticed how 
that close observer of nature, Bernardin de St. Pierre, 
depicted the same a century since in the same locality. 
“ This remnant of wreck had been washed bodily out of 
the deep water to within the outer barrier of reef on toa 
tedge, and was wholly out of the water, which position 
thus saved it from entire destruction, as only a portion of 
the enormous waves, which broke along the entire reef for 
miles, actually struck the remaining moiety, for the vessel 
had broken in two, and the stern-half had entirely been 
destroyed by the prodigious force of the breakers, the 
sound of which oceanic passion rose high above the din 
of the nearer dashing waves. Without the reef, sea and 
sky, ocean and air, were commingled, indistinguishable, 
“a complete annihilation of the linnt between sea and air.’ 
Within the reef, the shallower sea presented a most 
wonderful sight, such as few can describe; it was what 
Bernardin de St. Pierre, nearly a century since, termed + 
* Une vaste nappe décumes blanches creusés de vagues 
noires et profondes’ ; and what Victor Eugo, in his 
* Travailleurs de la Mer,’ has aptly described in European 
waters as ‘ d’eau de suvon,' * a sea of soapsuds and lather, 
the lather flying in snowy flakes like thistle-down. 
* The description given by Bernardin de St. Pierre of the view from the sea- 
shore on the north-east side of Mauritiusis so true, and so evidently sketched 
from nature, that it 
se briser sur fa céte s’avangait en mugissant jusqu’au fond des anses, et y 
jetait des galets & plus de cinquante pieds dans les terres; puis venant 2 se 
yill ever bear repetition. ‘*Chaque lame qui venait | 
retirer, elle découvrait une grande partie du lit du rivage, dont elle roulait | 
des cailloux avec un bruit rauque et afireux. La mer, soulevée par le vent 
grossissait 2 chaque instant, et tout le canal compris entre cette ile et lile 
Ambre n’était qu’une vaste nappe d’écumes blanches creusées de vagues 
noires et profondes. Ces écumes s’amassaient dans le fond des anses, & plus 
de six p.eds de hauteur, et le vent qui en balayait la surface les portait par- 
dessus l’escarpement du rivage A plus d’une demi-lieue dans les terres. A 
leurs flocons blancs et innombrables qui étaient chassés horizontalement jusqu 
"au pied des montagnes, on efit dit d'une neige qui sortait de la mer.’’— 
** Paul et Virginie’? (Ed. 1879, Hachette), 
2 «La mer & perte de vue était blanche; dix lieues d’eau de savon em- 
plissaient l’horizon.”’ 
} 
“[Both the above authors, incomparable in their 
respective lines, have, it will be observed, used somewhat 
similar imagery, which is sufficient proof of its fidelity to 
realistic facts. I have only seen one painters drawing 
which has at all even faintly attempted to copy these 
soapsuds of the sea, ‘Z’énorme écume échevelait toutes 
les roches; and that only on a small scale, viz. Mr. Frank 
Miles’ study of a curling wave before it breaks on ‘An 
Ocean Coast: Llangravieg, Cardiganshire’ (No. 342), in 
Gallery No. IV. of last year’s Academy.! The rendering 
of the blotches of foam,? which curdle on the hollow 
curved side and translucent crest of the breaking wave, 
are praiseworthy in their transcription, although their 
perspective has been blamed by some critics. ‘ L’écume 
ressemblait d la salive d’un léviathan’ Mr. Miles ought 
to have given to his drawing the lines from Keats, quoted 
by Ruskin as the Zer/ect expression of the peculiar action 
with which foam rolls down a long wave: 
**¢ Down whose green back the short-lived foam, all hoar, 
Bursts gradual with a wayward indolence.’ 
I cannot forbear giving Ruskin’s imagery, as bearing out 
the above similes :—“ The water from its prolonged agita- 
tion is beaten not into mere creaming foam, but into 
masses of accumulated yeast, which hang in ropes and 
| wreaths from wave to wave, and where one curls over to 
break, form a festoon like a drapery from its edge ; these 
are taken up by the wind, not in dissipating dust, but 
boldly in writhing, hanging, coiling inasses, which make 
the air white and thick as with snow, only the flakes are 
a foot or two long each: the surges themselves are full 
of foam in their very bodies, underneath, making them 
white all through, as the water is under a great cataract ; 
and their masses, being thus half water and half air, are 
torn to pieces by the wind whenever they rise, and carried 
away in roaring smoke, which chokes and strangles like 
actual water.’ See ‘Of Truth of Water’ (‘Modern 
Paiaters,’ vol. i. part 2, sec. v. Chap, III. p. 375.” 
S. P. OLIVER 
ON THE HEIGHTS OF THE RIVERS NILE 
AND THAMES 
OLONEL DONNELLY has put into my hands in- 
formation from which the following results have 
been obtained :— 
The information regarding the Nile has been derived 
from General Stone (Pacha), who has forwarded to the 
Science and Art Department a graphical representation 
exhibiting the height of the River Nile above the zero of 
the Cairo Nilometer for every five days, or six for each 
month from the beginning of 1849 to the end of 1878. 
The information regarding the Thames has been 
derived from Sir F. W. E. Nicolson, who has forwarded a 
daily record of the levels on the lower sill of Teddington 
Lock when the tidal water has all drained off. This 
record extends from the beginning of 1860 to the end of 
1880, 
At present it is impossible to deduce from these records 
the volume of water which passes in unit of time across a 
section of these rivers : nevertheless the results give us a 
good deal of information, for we may be sure that an 
increase in depth denotes an increase in the volume of 
the water carried by the river and a decrease in depth a 
diminution of the same. 
The results deduced I have embodied in a series of 
tables. In Table I. the yearly sum represents the whole 
area above the zero of the Cairo Nilometer of the 
graphical curve for the year in small squares whose base 
represents five days, and height one decimetre. 
+ An exhibition of paintings and drawings of “The Sea” isannounced this 
pe as to be held in the Gallery of the Fine Art Society, 148, New Bond 
2 “Les flocons d’écume, volant de toutes partes, ressemblaient A de la 
laine.”’ 
