GLEANINGS IN SCIENCE.*
ITNDEll this title, Dr. Molloy publishes a series of popular lectures on scientific subjects, nearly all of which were originally delivered before the Royal Dublin Society. These lectures, with perhaps one exception, treat of those questions of natural philosophy with which Dr. Molloy, as a Professor and Examiner of the Royal University of Ireland, has long been thoroughly acquainted. Hence the clear, easy manner with which the reverend Doctor explains even the most intricate points in the modern theory of heat, the production of the electric current, or the fascinating but difficult questions respecting the source of the sun's energy. Dr. Molloy dedi- cates his book to St. Patrick's College, Maynooth, " as a small token of my affection and gratitude." Such manifestations of good feeling are always pleasant and edifying, and it is to be hoped that the students of that famous ecclesiastical College may be induced by this kind thought of the author to read his book, and to take to heart the deep lessons it cannot fail to convey to reflecting minds. They will find there striking instances of that sublime order which pervades the universe, and speaks to us so eloquently of one Cause and one Will as its sole adequate explanation ; they will feel how small our little human disputes, political or otherwise, appear to minds familiar with those lofty and ennobling con- templations. They may realise, also, how necessary it is for those who are destined to lead and instruct others, to give to their own studies a breadth and solidity calculated to raise them above the illusions and passions of their disciples ; and the thoughts suggested by Dr. Molloy's book are well calcu- lated to effect that result, if studied with sufficient applica- tion and combined with the proper studies of the Christian philosopher and theologian.
Dr. Molloy's modesty has led him, quite uselessly, we should think, to place his Gleanings under the patronage of Ruskin, from whom he quotes this well-known passage :- " The great scientific men are all so eager in advance, that they have no time to popularise their discoveries, and if we can glean after them a little and make pictures of the things
and C
Gleaniix in Scienee. By Gerald Molloy, D.D., D.Bc. London : Macmillan o.
which science describes, we shall find the service a worthy one." Surely no one has need to apologise for taking up what is undoubtedly one of the most important offices in civilised society, provided he be competent to dis- charge the duties of such an office. Science has first to be made, then it must be taught ; and those most qualified by genius, special insight, peculiar opportunities, &c., to make science, are not always by any means the men most qualified to impart to others, especially in a popular way, what they were able to discover. This already indicates a natural division of labour. To work out principles is one department, and, of course, stands highest; to collect series of facts, to co-ordinate them, and to present them to the public in a lucid, comprehensive form, is a second department and this one is often worked best by men who, although lacking the higher form of genius, unite to their power of assimilating scientific facts a certain literary aptitude, without which the great art of imparting knowledge to others is seldom possessed. Hence, as Ruskin truly says, their " service is a worthy one," and we require their services nowadays more than ever. Specialism, the necessary evil of modern science, can only be made tolerable, and, indeed, practicable, on condition that the departments which stand closely related to the one department of our choice, be rendered sufficiently intelligible to us by accurate, compendious accounts of the matters with which those departments are concerned. Now, we could scarcely expect such works of exposition to be undertaken by the same men who are labouring day and night in a special department, engaged in original research. And what is true of books destined for students must be still more so of books intended for the general public. The posi- tion of the " populariser," if such a word may be allowed, is therefore, in our times, and probably for all times to come, finally established, for he is the expression of an absolute necessity. We wish, however, that all those who undertake the task were as well fitted for it as Dr. Molloy.
Per:iaps the lectures on " The Electric Light " form the most interesting portion of this book, inasmuch as they make us familiar with the methods and appliances to which we owe the marvels of modern Electric Lighting. The other lectures, useful and interesting as they must have proved to those for whom they were originally intended, are not perhaps of the same importance to the cultivated reader as they stand now published. On the other band, the lectures on the Electric Light present to us, arranged in a masterly manner, all the most essential facts respecting the production of the electric current, and the marvellous applications by which this current is made to yield the electric light. We are first introduced to a paper, now for ever memorable in the annals of science, which was read by Faraday in November, 1831, before the Royal Society of London. He announced his discovery that when a conductor the ends of which are connected together electrically, is moved in the presence of a magnet, a current of electricity is developed in the circuit during the time of its motion. Faraday further showed that the current is greatly intensified if the copper wire is wound round a bar of soft iron ; that the strength of the current is in proportion to the power of the magnet employed, and to the rapidity of the motion ;—also, that the current is equally produced in all cases, whether the magnet is at rest and the coil is moved, or the coil is at rest and the magnet moves. On these fundamental facts established by Faraday fifty-seven years ago, rest all the subsequent discoveries and improvements to which we owe the electric light of the present day.
Faraday, although fully conscious of the importance of his discovery, left to others the task of seeking out its practical applications. In the following year (1832), Pixii, of Paris, succeeded in building a machine for generating an electric current. This machine was soon materially improved, first by Saxton in 1833, and later on by Clarke. Then appears in 1857 what is known as Siemens' Armature, which showed that the power of electric machines was capable of being almost indefinitely increased. Soon after, we see realised the first appli- cations of the new discovery. In France, at Cape La Heve, near Le Havre, and at the South Foreland lighthouse in England, powerful machines were established with success for the regular production of electric light. The machine at the South Foreland, as Dr. Molloy remarks, is particularly in- teresting, because it was set up under the direction of Faraday himself, who at that time was scientific adviser to the Elder Brethren of Trinity House, and who thus had the satisfaction, after the lapse of thirty years, of seeing with his own eyes the realisation of his great idea. Other improvements followed in rapid succession until we reach the stage represented by the machine known as the " Edison-Hopkinson Dynamo," whose available electrical energy is stated to be over 90 per cent. of the mechanical energy applied to drive it, and is capable of maintaining more than a thousand incandescent lamps of sixteen-candle power each. In the year 1810, Sir Humphrey Davy had already produced the Electric Light at the Royal Institution of London ; but no regular application of this experiment could be made until the dynamo-electric machine, whose origin and progress we have rapidly described, had been constructed.
Dr. Molloy shows incidentally in the course of his lectures on the electric light, how the separate efforts of several in- ventors have led up gradually to the final results identified to-day with the names of Mr. Edison and Mr. Maxim in America, of Mr. Swan and Mr. Lane-Fox in England. Thus, when it became clear that carbon, and not platinum, as Mr. Edison at first believed, was the proper substance to be selected for the electric lamp, on account of the impossibility for any heat yet known to melt it, a new problem arose. Carbon could not be melted, but, on account of its great affinity for oxygen, it could easily be burned away. How to get rid of the air that supplies the oxygen became the great question. An American inventor named King tried and failed ; delay ensued. At last, Mr. Crookes, of London, was happy enough to discover the means of ensuring an almost perfect vacuum for the incandescent lamp. We give an account of this most interesting discovery, in Dr. Molloy 's own words :—
" Mr. Crookes was engaged between the years 18'73 and 1878 in malting experiments with his well-known radiometer. For these experiments he required a vacuum far more perfect than any which had been previously known. He therefore applied his rare powers of invention and contrivance to the improvement of Sprengel's mercurial air-pump. And so great was his success that we are now in possession of an air-pump which, with ease and certainty, can reduce the density of the air within a glass globe considerably below the millionth of an atmosphere."
Thus, oxygen being practically disposed of, carbon was found to be an available substance, and the electric light became soon what we now know it to be.
All the lectures contained in this volume are pervaded by a philosophical spirit which gives a sort of unity to the various subjects, outwardly unconnected, of which they treat. Thus, we are led on from the energy of mechanical motion to the energy of an electric current ; then, in the electric lamp we
are made to recognise in reality a contrivance for converting the energy of the electric current into the energy of heat and light. These transformations, as carried on through the
operations of the dynamo-electric machine, itself worked by means of a steam-engine, are derived evidently from the stored-up energy of coal, and the coal, as we know, represents the energy of the sun's rays, communicated in days long past to green plants whose life and work were the direct outcome of that energy. Thus, the mind is raised from the study of those practical facts by which our daily life is sustained and
our powers become increased, to the contemplation of those mighty problems which, however insoluble for our human science, yet never fail, as Wordsworth beautifully expresses it, to give us the sense of- " A presence that disturbs us with the joy Of elevated thoughts ; a sense sublime Of something far more deeply interfused, Whose dwelling is the light of setting suns, And the round ocean, and the living air, And the blue sky, and in the mind of man."
Previous page
