618 
NATURE 
[APRIL 29, 1897 
a greater mass overhead, and consequently greater heat. In the 
case of the Gothard, an increase of depth of 44 m. occasioned a 
rise in the temperature of 1° C. On this hypothesis, which is 
of course rough and approximate, in the middle of the work the 
thermometer will read about 4o° C. In the Cenisthe maximum 
temperature reached was 29° C.; but the workmen had to 
submit to this temperature for a short time only. In the 
Gothard the temperature of 31° C. had to be contended with for 
a long distance, and the sufferings were proportionately severe. 
Anemia and kindred diseases played havoc with the work- 
people. Some 60 per cent. of the workers, it is reckoned, 
were attacked ; and to prevent a similar disaster in the present 
undertaking, another set of problems, dealing with ventilation 
and sanitation, had to be considered as part of the entire 
mechanical difficulties that present themselves. 
The lines along which the main engineering problem has been 
solved are tolerably well known. The scheme contemplates the 
construction of two parallel tunnels, whose axes will be 
separated ly 17 metres. These two parallel roads will be con- 
nected at regular intervals by transversal galleries leading from 
one to the other, capable of being closed at will by air-tight 
doors. Only one of the main tunnels will at present receive its 
final dimensions, and be fully finished for trafic. The breadth 
will be 5 m., and the height above the sleepers 5°5 m. These 
dimensions will permit only a single line of rails to be laid, and 
provision is made in the middle of the tunnel for a siding 400 
m. long, so that two trains may pass in opposite directions. 
The object of the second tunnel, which will have a section of 
eight square metres, is mainly to ensure sufficient ventilation, 
and, indeed, to make the work in the main gallery possible. It 
was this ingenious thought, of carrying along simultaneously the 
two galleries, which has brought the perforation of the Simplon 
within the range of possibilities. This suggestion is due to 
Herr Brandt, of the firm with whom the contract has been 
placed. The distinguishing feature of this proposal is that it 
will ensure a current of air passing through the entire system of 
the tunnels. Evidently, if ventilating apparatus be placed at the 
entrance of either gallery, a current of air can be forced through 
one tunnel, through the transverse gallery at the end of the 
working (all the intermediate openings being closed), and out 
through the other tunnel. If it be objected that the construc- 
tion of the second gallery is a very expensive method of sup- 
plying fresh air to the workpeople, the answer is that, without 
some such means, the perforation is found to be impracticable. 
But the expense is not so great as it seems, because the second 
gallery can at no very great additional cost be made available 
for traffic when this increases to such an extent as to make the 
single line first laid insufficient. It is proposed to supply 
through this supplementary tunnel 50 cb.m. of air per second, 
by means of a current moving with the velocity of 13 miles an 
hour. Such a supply is far in advance of the quantity available 
at the Saint Gothard workings, and is to some extent founded 
or the amount that is found necessary to ventilate the Mersey 
tunnel. In this latter case the supply of fresh air, which no 
one who has made the journey from Birkenhead to Liverpool 
would say is excessive, is, it is true, four times greater than 
the quantity that will be pumped into the Simplon passage ; 
but the number of trains that pass in a day is considerably 
more, under the Mersey, than will be the case in the Simplon 
passage. Such a current may, therefore, be sufficient for 
the workmen, and will certainly tend to reduce the high 
temperature ; but the engineers will not trust to this means 
alone, to make the interior of the cutting endurable. Re- 
course will be had to the distribution, throughout the workings, 
of fine water-dust under considerable pressure. If the 
water, as it is hoped, can be delivered at the rock face at a 
temperature of 12° C., it can be employed with the happiest 
effect. Experiments made at Winterthur, before a committee 
of experts, proved that an air temperature of 4o°—5o° C. could 
be lowered to 15° by employing a water-dust of 12° C. under a 
pressure of five and a half atmospheres. When higher pressures 
are available a still more marked result is produced, and the 
abundant supply of water at both ends of the tunnel will permit 
this method to be tried under very favourable circumstances. 
This large supply of water, from the Rhone on the north side, 
and from Italian streams on the south, very fortunately permits 
the use of hydraulic machinery as a means of economically 
working the boring apparatus. In other works of similar 
character, compressed air has been the agent employed, against 
the use of which some objections have heen urged. We have 
NO. 1435, VOL. 55] 
here, therefore, the means of comparing the efficiency of the 
two methods, both in the operation of cutting through the hard 
gneiss rock, and the effect on the health of the operators, on 
whom the escape of the compressed air is said to work dis- 
advantageously. On the Arlberg, the natural surroundings of 
which are comparable with those to be met on the Simplon, the 
Brandt hydraulic perforating machine has given great satisfac- 
tion. It is contended by its supporters that, in a work of such 
magnitude, where the power has to be supplied from a great dis- 
tance, that hydraulic transmission is to be preferred to all other, 
because with it the loss of force is the least. From actual ex- 
periment on gneiss rock, it has been shown that a perforation 
I m. deep and 70 mm. diameter can be bored in 12 to 25 - 
minutes, and that consequently a daily advance of 5°85 m. can 
be reckoned upon. That M. Brandt has the greatest confidence 
in his invention and in his methods is shown by the fact that, 
in the contract which he has signed, he is willing to submit to a 
fine of 5000 francs a day in case the work is not completed in 
the five and ahalf years he allows himself. The total cost of 
the entire construction is computed at less than 3,000,000/. 
It is interesting to compare the rate of progress and cost of con- 
struction of the three tunnels which will compete for the Trans- 
Alpine traffic. In the case of the Mont Cenis tunnel, which 
represents the state of mechanical science some thirty years 
since, a year, approximately, was required to complete each 
kilometre at a cost of six millions of francs. ‘The Saint 
Gothard, about ten years later in date, proceeded twice as 
rapidly, while the cost of construction dropped to four million 
francs per kilometre. Herr Brandt, however, proposes to com- 
plete four kilometres per annum, at the same time reducing 
the expense per kilometre to one half that of the earliest tunnel. 
One may well wish that this sanguine estimate will be justified. 
ON THE COLOUR AND COLOUR-PATTERNS 
OF MOTHS AND BUTTERFLIES. 
PAPER by Mr. Alfred Goldsborough Mayer, on ‘‘ The 
Colour and Colour-Patterns of Moths and Butterflies ” 
(Proceedings of the Boston Society of Natural History, vol. 
xxvii. No. 14, pp. 243-330, March 1897), is a rather elaborate 
discussion of a subject which has lately attracted much attention; 
but though Mr. Mayer has made some interesting experiments 
and observations, his results are neither so novel nor so im- 
portant as he claims them to be. One of the most ‘interesting 
parts of the paper is the account of the development of wing- 
colours during the pupal state, a summary being given of 
previous researches, supplemented by a series of new observa- 
tions on common species of American moths and butterflies. 
The result arrived at is, that the wings are at first transparent, 
then white, then drab or dusky yellow, while all the purer and 
brighter colours arise later on, This is what might be expected 
from the general distribution of colour in lepidopterous insects, 
and has been indicated by Dr. Dixie and other writers as 
probable. 
Some ingenious experiments were made for the purpose of 
ascertaining whether the wing-scales were of any use in giving 
a greater hold on the air. The wings, with and without scales, 
were attached to a delicate pendulum, but no measurable 
difference in air-friction was found. Neither do the scales per- 
ceptibly strengthen the wings, hence it was concluded that they 
have been developed solely as colour-producing organs of use to 
the various species. 
A considerable space is devoted to the development of the 
colour-patterns of the Danaoid and Arcrzoid Heliconidee and 
the phenomena of mimicry. These are illustrated by four 
coloured plates intended to show the markings of a large 
number of species. These plates do not represent the ee 
themselves, but are ‘projected by Keeler’s method” on— 
rectangles of uniform size, which are supposed to afford more 
accurate means of comparison. This will seem to most 
naturalists to be a great mistake. It not only renders the 
patterns of the most familiar species almost unrecognisable, but 
it introduces many possibilities of error in the process of pr3- 
jection which even a comparison with the species represented 
may not enable us to detect. In the case of mimicking species 
ithas the further disadvantage of obscuring differences of out- 
line, and by irregular distortion giving undue prominence to 
what may be very slight differences in the actual species. In 
many mimicking species there is a wonderful similarity of 
