heat, used up in liquefying, is called latent. There is generally a change of bulk in the act of fusion; some substances expand, some diminish. Ice dissolves into water of less bulk, but most substances enlarge by liquefaction. It requires more heat at high than low temperature to warm liquid one degree. Most liquids contract with cold, but water expands from 39° F. to 32° F., and then crystallises. A glacier moves slowly on like a viscous body, although ice is not viscous. An indiarubber band suddenly stretched out becomes warmer; if you pull out a steel spring it becomes colder. The conversion of liquid into vapour requires an amount of latent heat which is generally much greater than the latent heat of fusion of the same substance, and when a gas is near its point of condensation, density increases more rapidly than the pressure. When it is at the point of condensation, the slightest increase of pressure condenses the whole into liquid, which seems contrary to the law"the pressure of a gas is proportional to its density." In the liquid form the density increases very slowly with the pressure. When temperature has attained a certain point, the properties of a liquid and those of the vapour continually approach to similarity, and above a certain temperature the properties of a liquid are not separated from those of a vapour by any apparent difference between them. Hence, the gaseous and liquid states are only different forms of the same condition of matter, and pass into each other without any interruption or breach of continuity. In one way you can see this, in another you cannot. Begin, for example, with water take this path B, a, A; return by A, a, B. We begin with water at B, we have water and saturated steam about a, then superheated steam till we reach A. On our way back we have no such stages-though when we reach B there is water as at first.1 M. Daubrée, by heating water to a very high temperature, and under pressure in strong glass tubes, produced silica in a crystallised condition similar to the crystals of quartz. There is a process for the production of carbon in the state of crystals. The products are very small diamonds. We mortals stoop to meanest matters, but our spirit rises from them to a heritage of grandeur. Potassium and sodium are remarkable: near akin in their specific gravities, their atomic weights, their chemical affinities, 1 "Recent Advances in Physical Science," p. 335: Prof. P. G. Tait, M.A. Changes in Consciousness. 379 and the properties of their compounds. Potassium fuses at 1445° F., sodium at 2077° F., but the alloy or mixture of the two is liquid at the ordinary temperature of the air. Cold is made to exist amidst hottest fire, and ice may be taken from a burning crucible. As to water, when in contact with ice, it cannot be cooled below zero without being converted into ice. In heating the water the ice melts, but the temperature of the mixture is never raised above 32° F. so long as the ice remains unmelted. Hence, the water contains a greater quantity of heat at 32° F. than ice contains at 32° F., and gives up or uses its heat in the effort to become ice. Physicists state that changes in consciousness are correlated with molecular motions of nerve-matter, which are highly differentiated forms of solar radiance. That is so, but under it all is a greater wonder. Even broad humour of this sort has a sort of mystery. A correspondent writes :— "One amusing incident of Jubilee week I have not seen mentioned in the papers, though many people observed it. The day before the great procession a costermonger's cart made a tour of the decorated streets in the West End, conveying the owner and party on a round of sight-seeing. The animal that drew it was made gay with a saddle-cloth, on which was conspicuously inscribed, 'The donkey will praise the Queen at intervals,'—a promise which was kept by a loud braying every few minutes, to the great amusement of the passers-by." 1 It seems too grand an explanation of a scene so laughable: "Vital energy differentiates the waves of solar radiance into those undulatory motions of nerve-matter which excite organic consciousness." Waves of this radiance speed to the earth at the rate of more than five hundred trillions to the second, and impart their energy so that we have growth of grass. Cattle browse on this, and hold in another form these metamorphosed sunbeams. Man, assimilating the nitrogenous tissues of the cow, builds up that wonderful white and grey nerve-tissue by the vital action of which is obtained the astonishing transformation of solar radiance into human consciousness. We know of nothing more wonderful than this continual miracle of progress by infinitesimal transformations, which make our brain "the market-place for thought." The Times, 1st July, 1897. Mental life comes out of physiological life; but mental activity originated in organisms by elementary modifications of external to internal relations, and passing from the automatism of lowest creatures to the highest act of consciousness in man; is a mystery that rescues the littleness of sunbeams and makes of them a pathway of living light by which man ascends to God. We can think of a world, all dark, beginning to vibrate differently, in various rapidities, until all gorgeous colours shine in light and beauty; or we may conceive the low rumblings of many motions acquiring tone until every musical note vibrates in worldwide oratorio; but infinitely more wonderful and varied is that operation by which God brings light of mind to men; and by their many prayers and praises makes the earth a vast cathedral; gives completed form of all completeness, that highest profession of all sweetness, Heavenly Love which makes our mortal life immortal. The Exactest of Sciences, Astronomy. The planetary motions, and those of the many planetoids, are so complex, and their relative positions so change, that the place of the general centre of gravity in relation to the mass of the sun is never the same for two consecutive moments; therefore, the disturbances of the sun's motion are most varying and complex; nor is any particle of the solar system in the same state or place during any two consecutive seconds. It is not by bewilderment, but true and beautiful; not brainless, but a manifest joy for ever whose loveliness increases. Immeasurable variety in connection with marvellous uniformity, is only exceeded by the same fact extended to all worlds. Vast and many are those worlds! To scientific gaze the diamond dust of the sky becomes suns and stars. Little cloudlets expand and reveal spheres of majesty, variable suns, binary and multiple systems, stars suddenly blazing forth in splendour, and mysterious dark orbs rolling in night. Great the variety, yet not a tithe of the various orders of bodies is known, we have but faint conception of the wonderfully varied realms within the stellar spaces. Not long ago, astronomers could scarcely allow that the vast depths, wherein the planets pursue their career, are the home of countless smaller bodies rushing in wide orbits round the solar mass. Few or none believed that those A Strange Firmament. 381 faintly gleaming lights, passing with silent swoop across a star group, leaving no trace of their existence and seeming of as little importance in the universe as a rain-drop or snowflake, indicated the close of a career which had often, by uncounted millions of miles, surpassed the utmost limits of the known planetary circles. These crowds of independent orbs, rushing disorderly round the sun, in no obedient family, would, it was considered, make the sweet bells of the planetary system jangle, be out of time and harsh nevertheless, the earth, sweeping on in her path, is exposed to cannonade from hundreds of meteor systems; and at critical periods is assaulted with heavier metal than that encountered in the second week of November; not only balls weighing many pounds, but of several tons, have been shot against her. We move and have our being in a strange firmament. How wonderful are the coloured suns! The brilliant Vega, a splendid steel-blue star, in the constellation Lyra, at midnight in winter, and earlier with the approach of spring, as it skirts the southern horizon, scintillates with red, blue and emerald light. Arcturus, low down in the east and north-east, in spring evenings twinkles yet more beautifully. Capella, towards the north, in summer nights, notably sparkles. Sirius, noblest of all These various colours are caused in part by our own atmosphere; but the stars are not wanting in real colours of their own. Sirius, Regulus, Spica, are white stars; Betelgeux, Aldebaran, Arcturus, Antares, are red; Procyon, Capella, the Pole-star, are yellow; Castor is slightly green; Vega and Altair are bluish; Castor has a green companion, Antares also, and there is the well-known "garnet star." In the double, triple, and multiple stars are all tints of the rainbow. "Here we have a green star with a deep blood-red companion, there an orange primary accompanied by a purple or indigo-blue satellite. White is found mixed with light or dark red, purple, ruby, or vermilion." One of the most startling facts-their colour is not unchangeable. Of old, Sirius was red, now it is white. A double star in Hercules changed in twelve years "from yellow, through grey, cherry red, and egregious red, to yellow again." These show that the stars are formed of different elements, and their vapours burn with variable brilliancy. There is Mira, the marvellous, shining brightly for two days thirteen hours and a half, as a star of the second magnitude; then, suddenly losing her light, in three hours and a half falls to the fourth magnitude; then, the brilliancy growing, in another three hours and a half `she re-attains her former lustre. Sometimes, as in the case of temporary stars, a spectrum of the fourth class is suddenly crossed by the bright lines of hydrogen, showing either a last discharge of red flames, or a flicker due to some last chance impact of meteoric matter. Many are the wonders pouring in upon us from Heaven's brink. Suns far off in space, and, for aught we know, important as our own, quickly blaze with wonderful brightness, and afterwards lose their splendour. A beautiful star appeared in Cassiopeia, A.D. 1572. It surpassed all other stars, was as Venus at her brightest, became of the first magnitude, exhibited various hues, and disappeared in March, 1574. In May, 1866, a star which had long shown feebly in the constellation of the Northern Crown, suddenly burst into flames, and attained the glory of a second magnitude star. Scientific men thought that the hydrogen encircling it passed from a relatively cool state, like that surrounding our sun and Capella and Aldebaran, into intense heat which made it glow with a hundred-fold of brightness. It is now, again, a star of the tenth magnitude. "For the years A.D. 807, 840, 1096, and 1607, and several others a great deficiency of the sun's light has been recorded. Thus in the annals of the year A.D. 536, the sun is said to have suffered a great diminution of light which continued fourteen months. From October A.D. 626, to the following June, a defalcation of light to the extent of one-half is recorded; and in A.D. 1547, during three days, the sun is said to have been so darkened that the stars were seen in the day-time. "1 "Glories infinite haunt us till they become a cheering type!" We can study changes in splendour, fatal catastrophes, the succession of phases of life in one particular star, and different simultaneous phases in many. Some stars start into life, others become older, others older and colder; sometimes 1 "Outlines of Astronomy:" Sir John F. W. Herschel, Bart. |