APRIL 22, 1897 | 
NATURE 
581 
= 
proper pronunciation may be approximately known. Exceptions 
should be in cases where the spelling has become by custom 
fixed, and occasionally it may be desirable to give both forms.” 
We write of Caucasus and Georgia, not Kavkaz and Grusia. 
But other legitimate exceptions in the Caucasian Provinces it 
might be hard to find. The fact that in the case of India the 
Society, for reasons of convenience, accepted the system, closely 
kindred to its own, already adopted and embodied in Hunter’s 
Official Gazetteer, can be in no way to the point in the case 
of the dominions of another Power. I can discover no reason- 
able ground whatever for the confusion of mind into which my 
critic has fallen. DouG tas W. FRESHFIELD. 
Alpine Club, April 9. 
““A Gigantic Geological Fault.” 
IN the very interesting description, by Captain A. H. McMahon, 
-of the features of the country on the southern borderlands of 
Afghanistan, which appears in the Geographical Journal for this 
month (April 1897, p. 393), he gives an account of a remark- 
able trench, or depression, running in a nearly N.N.E. and 
S.S.W. direction along the borders of Registan, which he was 
able to trace for 120 miles, but which may extend for a much 
greater distance through that wild region, and he clearly identi- 
fies it as the line of a large fault dividing a district composed of 
sedimentary rocks on the east, from one formed of igneous 
rocks on the west. On reading this account, the resemblance of 
this line of fracture to that of the Jordan-Arabah Valley at 
once suggested itself to my mind. The resemblance is nearly 
complete as regards the latter, from the head of the Gulf of 
Akabah as far as the northern end of the Dead Sea, at least ; 
except in this respect, that in the case of the Jordan-Arabah 
fault the sedimentary rocks occur on the west side, and the 
igneous rocks on the east. But the author has surely been 
misinformed as regards the statement, that ‘‘the length of this 
fault (which he traced) exceeds that of any fault-line as yet dis- 
covered on this earth” (p. 403). As far as actual observation 
goes, that of the Jordan-Arabah Valley is much longer ; for, 
measured only from the head of the Gulf of Akabah to the base 
of Hermon, it hasa length of 270 miles or more ; while there 
can be little doubt that it ranges still further north into the 
valley of Ccele-Syria. In the opposite direction, it may well be 
supposed that it follows the Gulf of Akabah for an unknown 
distance. It will thus be seen that the fault-line of the Jordan- 
Arabah Valley is very much longer than that of the border of 
Registan, described by Captain McMahon, as far as actual 
observation is concerned. But I am very far from asserting 
that either the one, or the other, exceeds in length that of any 
fault-line yet discovered. Epwarp HULL. 
Effects of Electrical Discharge on Photographic Plates. 
IN your issue of January 21, you published a note of mine on 
certain effects produced by charged conductors on sensitive 
plates. In the case of the radiograph of wire skeletons, I find 
that this is not an electrical effect, but is, in accordance with my 
alternative suggestion, undoubtedly due to the unequal loading 
of the film with silver particles, which set themselves in the 
pattern shown in the illustration when the gelatine is raised to 
a temperature near its melting point. 
The images of coins have been referred to by Mr. Brown and 
Mr. Sanford in their interesting letters, published January 28 and 
March 25 respectively (pp. 294, 485). 
I am also indebted to Prof. Smith, of Oxford, for a descrip-. 
tion and specimen of his beautiful ‘‘ Inductoscript,” in which 
very perfect images of coins and other objects are obtained by 
charging them inductively. 
In cases of brush discharge, such as that of the coins figured 
in illustration of my note, much of the effect is undoubtedly due 
to the luminous and ultra-violet radiation ; but this seems hardly 
to cover the whole ground. Both Prof. Smith and Mr. Sanford 
have got results which seem to point to some more direct elec- 
trical action, the latter having secured images of coins imbedded 
in gutta-percha and other insulators. To test this, I have placed 
a sensitive plate between two sheets of ebonite about +"; of an 
inch thick, which were placed upon a brass face-plate, and a 
coin laid upon the upper ebonite plate. The positive pole of the 
coil was connected with the brass plate, and the negative with 
the coin, and current passed for about two minutes. On de- 
velopment, an image of the coin came out, showing the design 
and a radiating halo, but out of focus and somewhat blurred, as 
might have been expected, as the coin was separated from the 
NO. 1434, VOL. 55] 
plate by the thickness of the ebonite sheet. This seems to 
point to some action other than that of the luminous discharge, 
which was plainly visible on the upper surface of the ebonite 
round the coin. 
It would be interesting to know the arrangement of condenser 
used by Mr. Sanford. JAMES ANSON. 
Fairheld House, Darlington, April 13. 
Curved Knives. 
Ir may interest your correspondent, Dr. Otis T. Mason, to 
know that the curved ‘‘ drawing-knife” described by him has 
representatives in Western (British) India. The Kolis (fishing 
races) of the Bombay coast wore lately, and some still wear, 
knives made by local blacksmiths, of which the blade, 2 to 3 
inches long, was shaped and edged like that of an English 
gardener’s knife. There was no hilt, but a tang curved re- 
versely to the blade, ending in a little curl. The whole figure 
was that of a manuscript capital S, with the lower curve heavily 
drawn and a fine finish at the top. Through the curl was passed 
a soft lanyard, and the whole worn round the neck, the knife 
hanging like a locket a little below the collar-bone. The way 
in which a man, holding the thin tang between the thumb and 
forefinger, or between two finger-knuckles, would cut anything, 
from a cable to a fish’s head, was the more wonderful, as he 
would often prefer bringing his breast near the object to un- 
slinging his knife. These knives are now passing out of use, 
displaced by old English and German clasp-knife blades, still 
without the hilts. The form must be very ancient, as bronze 
knives or razors of much the same shape are figured in most 
books about the European Bronze Age, and in Du Chaillu’s 
“Viking Age.”’ Iam inclined to suspect a flint origin for this 
form of ‘tool. Flint flakes in Western India, from Sind to the 
Konkan, often show a curved inner edge with traces of use. 
And if any one tries to cut wood with a hiltless flake of the 
sort, he will find the inner edge the most efficient. The Indian 
farrier’s ‘* drawing-knife”” is shaped like’ a_ sickle, squarely 
truncated to avoid the chance of injuring the horse’s foot (just 
as the English farrier’s knife is turned to one side for the same 
reason). Its hilt is a mere roll of coarse tape, but the grip of 
the hand is often that shown in Dr. Otis Mason’s illustration. 
The various hafled knives of India, with interior edges, belong 
to another class ; but the handle shown in this plate seems to 
be just an improvement on the simple blades mentioned above, 
and a very creditable one too. W. F. SINCLAIR. 
102 Cheyne Walk, Chelsea, April 9. 
Electrical Vibrations of Mercury. 
Tue following observations were made with a globule of 
mercury, about 14 cms. in diameter, placed in a photographic 
developing dish containing some ordinary tap water, the mer- 
cury being well covered with water. A 4-volt accumulator of 
6 ampere-hours’ capacity supplied the current. Two wires from 
the terminals served as anode and kathode ; the kathode had a 
short piece of fine wire attached, and this was so adjusted that 
it only just touched the mercury. 
(1) When the circuit was completed by dipping the anode 
into the water, the mercury, after a few seconds, became visibly 
flattened. 
(2) If the circuit was broken, or the mercury became de- 
tached from the kathode, it at once regained its original shape. 
(3) When the circuit was completed, and the mercury be- 
coming flattened broke away, it was thrown into a regular and 
continuous vibration. 3 , 
(4) The frequency and amplitude of the vibrations depended 
on the distance of the anode from the kathode, the frequency 
and amplitude increasing as the anode was brought nearer. 
(5) If the current was reversed, thus making the kathode an 
anode, the vibrations were not produced. 
(6) The vibrating mercury generally retained its circular 
shape, but sometimes it became almost square, or took the 
shape of a cross, which seemed to be produced by a rapid 
motion alternating at right angles. _ : 
(7) The water was thrown into circular waves, which corre- 
sponded to the vibrations of the mercury. _ f 
(8) If the circuit was broken, and an interval of time was 
allowed to elapse, and then again completed, a decided lag was 
observed between the ‘‘ making” of the circuit and the flattening 
of the mercury. If no appreciable lapse of time took place 
between “‘ make” and ‘‘ brealk,”’ the response was instantaneous. 
42 Henslowe Road, East Dulwich. ERNEST BRAUN. 
