Heliotrope

“ A similar instrument is the heliotrope, used principally for defining distant points in geodetic surveys, such as in the triangulation of India, and in the verification of the African arc of the meridian. ”

“ Poverty and sybaritism go as ill together as roses and purple paper, but I have always been too much given up to the gratification of the eyes and of the senses. How well I remember in my first girlhood, how I used to fill bowls with roses, lilacs and heliotrope, in the country June, and putting beneath my cheek a little pillow, whose crimson silk gave me delight, shut my eyes in my rough, unfinished little room, and the vales of Persia and the scented glades of the tropics were mine to wander through. ”

“ When they are planted out against the walls and pillars of the greenhouse or conservatory an abundance of highly perfumed blossoms will be supplied all the year round. From the end of May till October heliotropes are excellent for massing in beds in the open air by themselves or with other plants. Many florists’ varieties of the common heliotrope are known in cultivation. ”

“ A signalling party of three men was usually found sufficient to manipulate a pair of heliotropes—one for single, two for double reflection, according to the sun's position — and a lamp, throughout the night and day. Heliotropers were also employed at the observing stations to flash instructions to the signallers. ”

“ Therefore, we of Puffyloaf are taking today what may be the ultimate step toward purity: we are aerating our loaves with the noble gas helium, an element which remains virginal in the face of all chemical temptations and whose slim molecules are eleven times lighter than obese carbon dioxide—yes, noble uncontaminable helium, which, if it be a kind of ash, is yet the ash only of radioactive burning, accomplished or initiated entirely on the Sun, a safe 93 million miles from this planet. ”

“ The greatest dignity we may assign them is meta-element.
The formation of helium from the emanation was first shown by Ramsay and Soddy, and later confirmed by Indrikson, by Débierne, by Curie and Dewar, by Giesel and by Himstedt and Meyer. Helium, a conventional element which is devoid of any evidence of chemical affinity, is produced by or from radium, a conventional element, but the most active substance known. This occurs when the emanation is dry, and we have reason for assuming that the emanation may in reality be an active allotropic form of helium, as ozone is of oxygen. ”

“ If it be required to separate the helium which is often found in the gases given off by a thermal spring, they are subjected to the action of charcoal cooled with liquid air. The result is the absorption of the less volatile constituents, i.e. all except hydrogen and helium. The gaseous residue, with the addition of oxygen, is then sparked, and the water thus formed is removed together with the excess of oxygen, when helium alone remains. Or the separation may be effected by a method of fractionation as described above. ”

“ The radioactive atom in sinking to a lower
atomic weight casts out with enormous velocity an atom of helium.
It thus loses a definite portion of its mass and of its energy.
Helium which is chemically one of the most inert of the elements,
is, when possessed of such great kinetic energy, able to
penetrate and ionise the atoms which it meets in its path. It
spends its energy in the act of ionising them, coming to rest,
when it moves in air, in a few centimetres. ”

“ In contact with the heat of fusion of hydrogen and lithium to form the gaseous stellar ash called helium, any material rocket chamber would have been scattered instantly as incandescent vapor. But space warps stood firm in their place, squeezing with an atom-crushing pressure of their own, natural only at the centers of stars. And now there was no secondary arrangement for the conversion of such power as was released into electricity. Even the helium became pure radiation that emerged in a stream. ”

“ Roughly a million volumes of air contain 20 volumes of neon and helium, about 15 of the former to 5 of the latter, approximately 1 volume of hydrogen being associated with them, so that in view of the enormous amounts of oxygen that are produced, helium can be obtained in practically any quantity directly from the atmosphere. ”

“ But on applying the spectroscope to examine the character of the light which this gas emitted when submitted to the electric current, it yielded, to their amazement, the characteristic light of helium. Thus was the sun-element at last shown to be a terrestrial body, though no doubt a rare one. The circumstances that I have mentioned make helium for ever famous among the constituents of the universe. It will never be forgotten that though from henceforth it may be regarded as a terrestrial body, yet it was first discovered, not in the earth beneath our feet, but in the far-distant sun. ”

“ The helium formations do not reach the suns limb, and it is another puzzling detail that the spectrum of the disk shows no absorption line of anything like an intensity to correspond with the emission line of helium in the chromosphere. The prominences are of two kinds, quiescent and eruptive. Some of the former are to be seen at the limb on most occasions; they may hang for days about the same place; they reach altitudes of which the average is perhaps 20,000 m., and show the spectral lines of hydrogen and helium. ”

“ A fact which may have a significance which we cannot at present see is that the emanation from radium gradually and spontaneously changes into helium, an alchemistical feat of nature that has opened many curious vistas to speculative thinkers. The eruptive prominences, which do not spread horizontally like the others, but ascend with marvelous velocity to elevations of half a million miles or more, are apparently composed largely of metallic vapors—i.e. metals which are usually solid on the earth, but which at solar temperatures are kept in a volatilized state. ”

“ And, as the weight of helium is one eighth of that of an equal volume of oxygen, the weight of a molecule of helium will be the eighth part of 32, or 4. Similarly, the molecular weight of argon compared with that of an atom of oxygen taken as 16 will be 40, But the question has still to be answered: Does a molecule of helium or of argon resemble a molecule of oxygen in consisting of two atoms; or does it consist of one atom or of more than two?
It is believed that when heat is put into a gas, it is expended in causing the molecules to move. ”

“ The helium atom (or, for that matter, the uranium atom) can on occasion masquerade in the scanty attire of the hydrogen atom. Normal helium has two planet electrons; but if one of these is lost, it becomes hydrogen-like and copies the simple hydrogen system on a different scale. It is significant that the Pickering Series appears only in the very hottest stars—in conditions likely to cause loss of an electron. The difference between hydrogen and hydrogen-like helium is firstly the difference of atomic weight; the helium nucleus is four times as massive. ”

“ Weight for weight, it emits during its change an amount of energy at least one million times greater than any molecular compound known (see section 249) . In addition, it must be supposed that the rate of breaking up of the helium compound is independent of great ranges of temperature—a result never before observed in any molecular change. The helium compound in its breaking up must give rise to the peculiar radiations and also pass through the successive radio-active changes observed in radium. ”

“ In every single instance I have obtained negative results, and, as far as my experiments go, helium remains a permanent gas, and apparently much more difficult to liquefy than even hydrogen. The small quantity of the gas at my disposal, and, indeed, the extreme rarity of the minerals from which it is obtained, compelled me to carry out my investigation on a very small scale. Using a larger apparatus, and working at a much higher pressure, I could have submitted the gas to greater expansion. ”

“ By the use of these methods it has been shown that the velocities of the ions in a given gas are the same whether the ionization is produced by Röntgen rays, radioactive substances, ultra-violet light, or by the discharge of electricity from points. When the ionization is produced by chemical action the ions are very much less mobile, moving in the same electric field with a velocity less than one-thousandth part of the velocity of the first kind of ions. ”

“ I make the supposition that hydrogen, and not helium, will be the sustaining gas. For commercial aviation it has many advantages, for helium is dearer and rarer, and has about twenty per cent. less lift. Contrary to general belief, a flight in an airship filled with hydrogen, [Pg 157] subject to proper precautions, has no greater fire risk than living near a gas factory. ”

“ The pressure of the earth acts as my generator. The pressure action on the filaments of platinum, and several compositions I have no time to explain now, causes heat. Call it friction of compressed air, if you wish. As neon gases carry an electric spark, so does this helium carry the power generated by earth pressure. The pressure below earth acts on the delicate coils and points of my generator. This bit of power is carried into the helium tubes, and by a system of vacuum power, is increased millions of times. Thus, the tiny spark of a cigar lighter would electrocute a hundred men! ”

“ Now the kinetic theory of gases informs us that their molecules are continually flying in all directions with velocities varying with the nature and the temperature of the gas. The maximum velocity of the molecules of oxygen is 1.8 miles per second, of hydrogen 7.4 miles, of nitrogen 2 miles, of water vapour 2.5 miles. It is evident, then, that the force of the earth's attraction is sufficient permanently to retain all these gases except hydrogen, and in fact there is no gaseous hydrogen in the atmosphere, that element being found on the earth only in combination with other substances. ”

“ On the views outlined, we should expect the helium nucleus of charge to be built up of four protons and two electrons. The loss of mass in forming this nucleus indicates that a large amount of energy must be liberated during its formation. If this be the case, the helium nucleus must be such a stable structure that the combined energy of four or five of the swiftest α particles would be necessary to effect its disruption. ”

“ In a similar manner we find that the second lightest gas, helium, at a temperature of 150° C. (300° F.) , possesses a molecular velocity of 1.62 km. (1.1 miles) per second. This is less than the 2 km. (1.24 miles) per second necessary to leave the Moon’s sphere of attraction. But all helium molecules do not move at the same speed; some are faster127 and some slower than the average. Those moving at a higher rate than 2 km. (1.24 miles) per second constitute a considerable fraction of the total. ”

“ If we were to take elements of much greater atomic weight the residues would have high atomic weights also and these heavy atoms are not detected by the photographic plate nearly so easily as the lighter ones like helium, so that even if there were the same number of the atoms of the residue as of the helium present In the tube the helium might show on the plate while the residues did not. ”

“ Properties.—All attempts to make helium enter into stable chemical union have hitherto proved unsuccessful. The gas is in all probability only mechanically retained in the minerals in which it is found. Jacquerod and Perrot have found that quartz-glass is freely permeable to helium below a red-heat (Compt. rend., 1904, 139, p. 789) . The effect is even perceptible at a temperature as low as 220° C. Hydrogen, and, in a much less degree, oxygen and nitrogen, will also permeate silica, but only at higher temperatures. ”

“ This conclusion could be indirectly tested by examining whether helium is produced in other substances besides radium, for example, in actinium and polonium.
The experimental determination of the origin of helium is beset with great difficulty on all sides. If the a particle is a helium atom, the total volume of helium produced in an emanation tube should be three times the initial volume of the emanation present, since the emanation in its rapid changes gives rise to three products each of which emits α particles. ”

“ The barometer pressure is only eleven pounds, which compensates for the excess of oxygen. The helium is a good indication of the radioactivity which must have produced the gas overhead, since helium is one of the ultimate products of radium disintegration. The oxygen must have come largely from the breaking up of carbon dioxide by plant life. ”

“ What is more, each molecule of the gas is bound, sooner or later, to attain this maximum velocity of its kind merely on the doctrine of chances. When it is attained, the molecule of water vapor at the rate of two and one third miles a second, and the molecule of hydrogen actually at seven miles at second, six hundred times as fast as our fastest express train.
Now, if a body, whether it be a molecule or a cannon-ball, be projected away from the earth's surface, the earth will at once try to pull it down again: this instinctive holding on of Mother Earth to what she has we call gravity. ”

“ But the molecules are continually changing their velocity and may sometimes attain a speed which is seven times as great as the average. Suppose, therefore, that a certain quantity of hydrogen were diffused through our air, every now and then a molecule of hydrogen in its wanderings would attain the upper limit of our atmosphere, and then it would occasionally happen that with its proper speed it would cross out into space beyond the region in which its movements would be interfered with by the collisions between other atmospheric molecules. ”