March 22, 1883] 
NALOURE 
491 
the utmost difficulty in handling keys, setting instruments 
and entering my observations. Usually so laden was the 
air with moisture and so very dense and lasting was the 
cloud-fog that, even when no rain had actually fallen, 
all the fixings and instruments were dripping; and al- 
though, of course, I made a point of wiping the dry 
bulb, it almost immediately became wet again. Occa- 
sionally I timed the interval between wiping and fresh 
condensation on the bulb, and have found it wet again 
within ¢izrty seconds. 
After November 1, then, 1 had to discontinue the work, 
The hut had become choked with snow, and the carrying 
on of the undertaking satisfactorily impossible. I was, 
however, satisfied ; and very pleased that I had secured 
Bie months’ observations without the break of a single 
ay. 
It is not my part to refer in this paper to any results. 
Such I must in duty leave to be discussed and made 
known by the Scottish Meteorological Society. But, 
from what I myself know of the meteorology of Ben 
Nevis from the experience of two summers and autumns, 
I do most strongly urge the establishment of a permanent 
observatory on the summit, firmly believing that most im- 
portant and unexpected results will accrue to meteorology 
from continuous observations there. Such, in connection 
with others at the sea-level, would in my opinion enable 
the energetic staff at the Meteorological Office, under Mr. 
Robert H. Scott’s able direction, to forecast storms with 
far greater certainty. 
I cannot conclude this account without expressing my 
best acknowledgments to Dr. Angus Smith for placing at 
my disposal his apparatus for measuring the actinism of 
light, which I consider an immense acquisition to a 
meteorological observatory; to Mr. John Browning for 
his rainband spectroscope ; to Messrs. Negretti and 
Zambra for their clock-hygrometer ; and finally to the 
Scottish Meteorological Society for the kind encourage- 
ment and liberal assistance they have given me. 
CLEMENT LINDLEY WRAGGE 
HYDROGEN WHISTLES 
[= may be recollected by some of the readers of NATURE 
that a few years ago! I contrived a whistle for testing 
the upper limits of the power of hearing very shrill notes 
by different men and animals. When properly made, it 
easily suffices to do this, in the case of men and most 
animals, but it cannot, neither can any other instrument 
hitherto devised, emit such notes as it is conceivable that 
insects may hear. The problem whether any insects can 
hear notes whose numbers of vibrations per second is 
manyfold greater than those of the notes audible to men 
has not yet been fairly put to the test of experiment. I 
wish to show that this can now be done. 
The whistles of which I speak have their lower ends 
closed with a piston that admits of being inserted more 
or less deeply, and thus of varying the depth of the 
whistle and consequently its note; but as a whistle will 
not give its proper note unless its depth be greater than 
its width, say, 14 times as much, and as the depth of a 
whistle that gives, say, 24,000 vibrations per second is 
is only o'14 inch, it follows that their bores must be very 
small, and that a limit of minuteness is soon reached. 
Having had occasion lately to reconsider the subject, it 
occurred to me that I cculd greatly increase the shrillness 
of any whistle by blowing a gas through it that was lighter 
than common air. 
_ The number of vibrations per second caused by whistles 
is inversely proportional to the specific gravity of the gas 
that is blown through them; therefore by the use of 
hydrogen, which is thirteen times lighter than air, the 
* “South Kensington Conferences, in “connection with Loan Exhibition 
of Scientific Apparatus, 1876,” p. 61. 
number of vibrations per second produced by a given 
whistle would be increased thirteenfold. 
I have made experiments with most satisfactory results 
with common coal gas, whose specific gravity, though 
much greater than that of hydrogen, is not much more than 
half that of common air, and I have little doubt in con- 
sequence that a number of vibrations may be excited by 
one of my small-bore whistles through the use of hydro- 
gen gas, that very largely exceeds the number attainable 
hitherto in any other way. They would of course fail to 
excite the sense of sound in any of ourselves, or 
perhaps to produce any physical effect that we can 
appreciate, whether on sensitive flames or otherwise, 
and the note to those creatures, if any, who could hear 
it, would be feebler on account of the lightness of the 
medium in which the vibrations originated, but it would 
be (so far as I can anticipate) a true note, and ought to be 
powerful enough to be audible at the short distances at 
which small creatures may be tested. The whistle I used 
was made forme by Hawksley, 357, Oxford Street ; its 
bore is o'04 inch diameter, and it givesa loud note for its 
size. After some prefatory trials, I proceeded as fol- 
lows:—I attached the whistle to a gas jet by a short 
indiarubber tube. Then, without turning on the gas, I 
retested my range of hearing by setting the piston at 
various lengths and giving sharp squeezes to the tube as 
it lay in the hollow of my hand. The effect of each 
squeeze was to force a little air through the whistle, and 
to cause it to emit'a sharp “cheep.” When I relaxed the 
grasp, air was sucked in through the whistle, and the 
tube became again filled with air, ready for another 
squeeze. 
My range of hearing proved to be such that when the 
depth of the whistle was 0°13 inch, I could hear no 
musical note at all—only a puff; at o'14 inch I could just 
perceive a very faint musical note enveloped, as it were, in 
much puff; even at 0°20 some little puff remained, but 
before 0°25 the note had become purely musical. This 
having been established, I kept the whistle set at 0°25 and 
turned the gas on, giving it abundance of time to expel 
all air from the tube. Then, turning the stopcock to shut 
the indiarubber tube from behind, I gave a sharp squeeze 
as previously, but the whistle, instead of emitting a pure 
note, gave to me just the same barely perceptible sound 
that it did when it was set at o114. I relaxed my grasp 
and instantly retightened it, and then the whistle emitted 
a pure note. A little common air had regurgitated into 
the whistle when my grasp was relaxed, and it was the 
reissue of this that gave the note. J repeated the experi- 
ment several times with the same result. With a depth 
of 0:24 I could hear no note at all when using the gas. 
Then I pulled out the piston to 0°35, and the gas gave a 
clear musical note; on the second squeeze the note was 
considerably deepened. The specific gravity of the gas 
from the jet, as calculated from these data, would be to 
that of the air at the time, as 14 to 25, or as 0°56 to 1. 
This happens to be the specific gravity of carburetted 
hydrogen, but that of common street gas is heavier. 
Perhaps my measurements were not quite accurate; 
probably the note given by the gas being really fainter 
(though not perceptibly so) than that given by air 
somewhat falsified the judgment. A very slight differ- 
ence in the data would raise the 0°56 to 0°60 or more. 
By the use of hydrogen the little whistle when set at 0°14 
inches would produce 312,000 vibrations per second. I 
know by experiment on others that it will give a true 
musical note when made much shorter than this, and I 
see no cause to doubt that it will sound truly at half the 
above length, and therefore be capable of emitting twice 
the akove enormous number of vibrations per second. 
Mr. Hawksley is making for me an apparatus with 
small gas bag for hydrogen pure or diluted, valves, and 
an indiarubber ball to squeeze, to enable hydrogen to 
be used with the whistle when desired. The whistle is 
