40 
NATURE 
[May 14, 1885 
aS Se 
would be available for carbonising, oil and ammonia being re- 
moved from it by efficient scrubbing. The author was of opinion 
that nothing was known practically of what happens when coal 
is distilled, and that the coking of coals and manufacture of gas 
were now only empirical operations, and could not be conducted 
scientifically, with our present imperfect knowledge, but that 
the interests involved were so great, the subject being one of 
national importance, that failure to initiate and execute the 
necessary systematic experiments without further loss of time 
would be inexcusable. 
On the last day of the meeting Mr. Carnegie’s paper on 
‘* Natural Gas Fuel and its Application to Manufacturing Pur- 
poses” was read. This fuel is found in the Pittsburg district, 
and one of the wells is estimated as yielding 30,009,000 cubic 
feet of gas in the twenty-four hours ; the pressure of the gas as 
it issues from the mouth of the well is about 200 lbs. to the 
square inch, and even at the works, nine miles from the wells, it 
is 75 lbs. per square inch. Eleven lines of pipe convey the gas 
from the various wells to the manufacturing establishments in 
and around Pittsburg. The number of men whose labour will 
be dispensed with when gas is generally used is 5000. In the 
steel-rail mills, for instance, where before would have been seen 
thirty stokers, stripped to the waist, firing boilers which require 
a supply of about 400 tons of coal in twenty-four hours—ninety 
firemen in all being employed, each working eight hours—there 
would now be found one man walking around the boiler-house, 
simply watching the water-gauges, and not a particle of smoke 
is to be seen. 
Dr. Hermann Wedding’s paper on ‘‘ The Properties of Mall- 
eable Iron deduced from its Microscopic Structure ” draws atten- 
tion to the value of microscopic analysis, as, though the chemical 
and physical properties of iron are closely connected, the one 
cannot be directly deduced from a knowledge of the other, nor 
do either of these aid in acquiring a knowledge of the mechani- 
cal properties. The pieces of iron to be tested are carefully 
polished, and then etched with very dilute nitric acid. After 
etching, the section is carefully heated, whereupon the portions 
attacked acquire varying tints, mostly golden-yellow, purple-red, 
violet, or dark blue. It is the difference of colour that is cha- 
racteristic. As regards the formation of grains and fibres, the 
size of grain increases with slowness of cooling, and decreases 
with increase in the proportion of carbon up to 2 per cent. 
Each individual grain in malleable iron is ductile, the mallea- 
bility of the entire piece depending on that of the separate 
grains, which are drawn out into fibres ; the strength of fibrous 
iron depending on the fact that, like the individual hemp-fibres 
in a rope, the fibres lie with their ends in various sections. The 
microscope shows, further, that none of these wires or fibres is 
directly connected with its neighbours, either in a longitudinal 
or lateral direction. In fact each fibre may, by careful etching, 
be picked out like those of a muscle in the human body. The 
paper treats also of the constitution of individual iron crystals 
and of welding. The general result of the analysis shows that 
the strength of a finished piece of iron depends on the sectional 
area of the mass of iron it contains, the slag inclusions in weld- 
iron and blow-holes in ingot-iron being deducted. 
It was announced that the autumn meeting of the Institute 
would be held at Glasgow. 
SUNLIGHT AND THE EARTH'S 
ATMOSPHERE* 
Il. 
WE have been compared to creatures living at the bottom of 
the sea who frame their deceptive traditional notions of what 
the sun is like from the feeble changed rays which sift down to 
them. Though such creatures could not rise to the surface, they 
might swim up towards it, and if these rays grew hotter, 
brighter, and bluer as they ascended, it would be almost within 
the capacity of a fish’s mind to guess that they are still brighter 
and bluer at the top. 
Since we children of the earth, while dwelling on it, are 
always at the bottom of a sea, though of another sort, the most 
direct method of proof I spoke of, is merely to goup as far as we 
can and observe what happens, though as we are men, and not 
fishes, something more may fairly be expected of our intelligence 
than of theirs. 
We will not only guess, but measure and reason, and in par- 
™ Lecture delivered at the Royal Institution, April 17, 1885, by S. P. 
Langley. Communicated by the author. Continued from p. 20. 
ticular we will first, while still at the bottom of the mountain, 
draw the light and heat out into a spectrum, and analyse every 
part of it by some method that will enable us to explore the 
invisible as well as record the visible. Then we will ascend 
many miles into the air, meeting the rays on the way down, 
before the sifting process has done its whole work, and there 
analyse the light all over again, so as to be able to learn the 
different proportions in which the different rays have been 
absorbed, and, by studying the action on each separate ray, to 
prove the state of things which must have existed before this 
sifting —this selective absorption—began. 
It may seem at first that we cannot ascend far enough to do 
much good, since the surface of our aérial ocean is hundreds of 
miles overhead; but we must remember that the air grows 
thinner as we ascend, the lower atmosphere being so much 
denser, that about one-half the whole substance or mass of it. lies: 
within the first four miles, which is a less height than the tops of 
some mountains. Every high mountain, however, will not do, 
for ours must not only be very high, but very steep, so that the 
station we choose at the bottom may be almost under the station 
we are afterwards to occupy at the top. 
Besides we are not going to climb a lofty lonely summit like 
tourists to spend an hour, but to spend weeks ; so that we must 
have fire and shelter, and above all we must have dry air to get 
clear skies. First I thought of the Peak of Teneriffe, but after- 
wards some point in the territories of the United States seemed 
preferable, particularly as the Government offered to give the 
Expedition, through the Signal Service, and under the direction 
of its head, General Hazen, material help in transportation and 
a military escort, if needed, any where in its own dominions. 
No summit in the eastern part of the United States rises much 
over 7000 feet, and though the great Rocky Mountains reach 
double this, their tops are the home of fog and mist, so that the 
desired conditions, if met at all, could only be found on the other 
side of the Continent in Southern California, where the summits 
of the Sierra Nevadas rise precipitously out of the dry air of 
the great wastes in lonely peaks, which look eastward down 
from a height of nearly 15,000 feet upon the desert lands. 
This remote region was, at the time I speak of, almost un- 
explored, and its highest peak, Mount Whitney, had been but 
once or twice ascended, but was represented to be all we desired 
could we once climb it. As there was great doubt whether our 
apparatus, weighing several thousand pounds, could possibly be 
taken to the top, and we had to travel 3000 miles even to get 
where the chief difficulties would begin, and make a desert 
journey of 150 miles after leaving the cars, it may be asked why 
we committed ourselves to such an immense journey to face such 
unknown risks of failure. The answer must be that mountains 
of easy ascent and 15,000 feet high are not to be found at our 
doors, and that these risks were involved in the nature of our 
novel experiment, so that we started out from no love of mere 
adventure, but from necessity, much into the unknown. The 
liberality of acitizen of Pittsburgh, to whose encouragement the 
enterprise was due, had furnished the costly and delicate appa- 
ratus for the expedition, and that of the trans-continental rail- 
roads, enabled us to take this precious freight along in a private 
car, which carried a kitchen, a steward, a cook, and an ample 
larder besides. 
In this we crossed the entire continent from ocean to ocean, 
stopped at San Francisco for the military escort, went 300 miles 
south so as to get below the mountains, and then turned east- 
ward again on to the desert, with the Sierras to the north of us, 
after a journey which would have been unalloyed pleasure except 
for the anticipation of what was coming as soon as we left our 
car. 1 do not indeed know that one feels the triumphs of 
civilisation over the opposing forces of Nature anywhere more 
than by the sharp contrasts which the marvellous luxury of recent 
railroad accommodation gives to the life of the desert. When 
one is in the centre of one of the great barren regions of the 
globe, and, after looking out from the windows of the flying 
train on its scorched wastes for lonely leagues of habitless deso- 
lation, turns to his well-furnished dinner-table, and the fruit and 
ices of his desert, he need not envy the heroes of Oriental 
story who were carried across dreadful solitudes in a single night 
on the backs of flying genii. Ours brought us over 3000 miles 
to the Mojave desert. It was growing hotter and hotter when 
the train stopped in the midst of vast sandwastes a little after 
midnight. Roused from our sleep, we stepped on to the brown 
sand and saw our luxurious car roll away in the distance, expe- 
riencing a transition from the conditions of civilisation to those 
almost of barbarism, as sharp as could well be imagined. We 
