Imagens das páginas
PDF
ePub

The inner

the new Macbeth is not far from being true. truth of this play is wholly separate from its grandeur, except as both are expressed by its inimitable language; and is only partially and briefly identified with its incomparable beauty. But when the truth has been long obscured, and upon manifestation is rudely and crudely challenged, it is necessary to stand up for it. The grandeur of "Macbeth" may probably be best enjoyed by the fancy without scenic auxiliaries. Its beauty-except so far as it lies in Lady Macbeth's tender sorrowfulness-is somewhat clouded in a representation which undoubtedly does not as a whole sound the full diapason of the poet's matchless eloquence. But the truth is there, with but few and insignificant qualifications, and for its own sake, and for the credit of acting as the most efficient method of elucidatory criticism, cannot be too closely or admiringly studied. Surely every one must be encouraged and spurred to such study, who, going back to his Johnson, reads the extraordinary statement that this play "has no nice discrimination of character," the events being "too great to admit of the influence of particular dispositions, and the course of the action necessarily" determining "the conduct of the agents." I will add, that we can all feel what criticism owes to the stage, when we are told on the same high authority that the effect of the play is to make Lady Macbeth "merely detested." This, after all Shakspeare has done, by the suggestion of her wifely solicitude and self-abnegation, to shelter her with the gentle veil of pity! Well might Gervinus say that the clever player will always be a better interpreter of Shakspeare than the most learned commentator!

The suggestion I have myself made for the right reading of the play is a small one, but I am impressed with its ethical value, and with the fact that here at least criticism must advance where acting can hardly follow it.

Only in the greatest dramatists can we expect to find lying, half-lost amidst stirring action and bold spectacle, minute but pregnant casualties of moral being and character. None the less is it our duty to seek them out. We should not be deterred by any fear such as a great French critic has expressed, of appearing to embark on frivolous subjects. The delicate contrast between the hardsinning of Lady Macbeth and the timorous sinning of her husband is founded in a difference of attitude towards supernatural religion which might be instanced in every company, and pursued into every relation of circumstances in which differing people have to make choice between good and evil. Such studies can never be unprofitable, nor will they ever cease to occupy the highest genius amongst a people saturated as we are with ideas of moral responsibility under religious sanctions.

For us there is no golden age of ancient beauty, nor any beaming vale of Tempe. Not for us are the rounded forms and seamless draperies of the Greek ideal. Not for us the lightsome laughter of pastoral gaiety, or the sunny merriment of sylvan revels. We cannot prattle and gesticulate in Gallic epigram, nor pose and declaim in Spanish pride, nor lose ourselves in Teutonic simplicities, nor find even in docile picturesque religion a talisman or an anodyne.

"We look before and after,

We pine for what is not :
Our sincerest laughter

With some pain is fraught;

Our sweetest songs are those that tell of saddest thought."

And the truest of our great plays unfolds, not only the majesty and mystery of tragedy, but the common exigencies of daily morals.

ON ELECTRICITY COMPARED WITH HEAT AS A

SOURCE OF MECHANICAL POWER.

By J. CAMPBELL BROWN, D.Sc., ETC.

In what direction can we reasonably look for a substitute for coal?

Since the popular mind began to recognise the fact that the known sources of coal within our reach are rapidly becoming exhausted, and cannot last many hundred years, and especially since the advanced price of coal forced the attention of large employers of steam-power to the difficulties of the not very distant future, many persons have been induced, by the great advances which have been made in the practical application of electricity, to contemplate the substitution of electricity for heat as a source of mechanical power. From a scientific point of view there is nothing absurd or impossible in the proposition to employ electricity as a source of mechanical motion; although the probability or possibility of its being practically advantageous may be a subject for discussion.

The doctrine of the correlation and mutual convertibility of all the physical forces is now thoroughly established;*

* Law of conservation of energy. The amount of force associated with matter is definite and constant. Whenever a given amount of energy in one form disappears, it reappears as work done, either as motion, heat, light or some other form, the amount of which is exactly equivalent to the amount which has disappeared. Mechanical equivalents of heat and electricity:— The amount of heat required to

When converted into motion, can

[merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][ocr errors][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][merged small]

The amount of electricity required to eliminate 1 gramme of hydrogen and

8 grammes of oxygen from water, is equivalent to about 34,000 units of heat

[blocks in formation]

and any one of these forces which happens to be at our disposal may be taken as reasonably as another for conversion into mechanical motion. Although a given quantity of one form of force always yields, when converted, an equivalent quantity of other forms of force, none of it being ever destroyed or lost, yet we are never able, with the imperfect machines which we can make, practically to convert the whole of a given force into the precise form of force which we require, nor can we ever transfer the whole of any force from one machine to another; a portion of the force is always converted into some form which we do not want; it is practically as bad as lost. The most familiar illustration of this impossibility is the loss of motion by friction, which occurs when we transfer mechanical motion from one machine or part of a machine to another; some of the mechanical motion is converted into an equivalent quantity of heat, and hence for mechanical purposes is lost. The greater the number of conversions into different forms which a given amount of energy undergoes before it reaches the point to which we want to apply it, the smaller will be the ultimate fraction available, and the greater will be the proportion of force lost, just as an increase in the number of different parts of a machine increases the loss by friction.

In the conversion of heat into mechanical motion by means of the steam-engine, so much heat is lost (using the word lost in a popular and unphilosophical sense) that only a small fraction, about one-ninth, of the heat generated in the furnace can be ultimately utilised as mechanical power. One pound of coal will convert rather more than ten pounds of water into steam; or will raise upwards of 10,000 lbs. of water 1° Fahrenheit, that is, it will do about 8 millions of foot-lbs. of work. One grain of coal, when burnt, develops heat equivalent to about 1,215 foot-lbs., but it only enables the best Cornish engines to do 143 foot-lbs. of work.

In constructing electrical engines, the great difficulty hitherto has been to get a considerable fraction of the given force-electricity-converted into the required forcemechanical motion-without being dissipated in some other form, such as heat. It is true that Professor Jacobi constructed an electro-magnetic engine which propelled a small boat, with twelve persons on board, at the rate of four miles an hour; Mr. Robert Davidson drove an electric locomotive on the Edinburgh and Glasgow Railway at the same rate; and Professor Page constructed a four- or five-horse power reciprocating engine. An idea of the principle on which these machines were constructed, may be gained by examining the toy electro-motive pump placed on the table. No electro-motive engines have yet been made sufficiently perfect and convenient for general use, but there is no doubt that they can be very much improved, and that engines can be made, and probably will be made, capable of producing every variety of motion much more conveniently, and with much less loss of power, than any constructed upon principles hitherto known. By means of Gramme's machines, similar to the one upon the table, M. Breguet converted a known amount of motion into electricity by one machine, and then passing the current through the second machine, converted that electricity again into motion, and found the loss to be only thirty per cent. This is by far the best result hitherto obtained, and the motion is continuous and rotatory.

It is therefore desirable to enquire how far it is worth our while to endeavour to make electrical currents or magnetism more available as a prime mover of machinery.

An electro-magnetic machine ought to yield force equal to 112 foot-lbs. for every grain of zinc consumed in the battery; but in practice, only the equivalent of 70 or 80 footlbs. can be obtained as a current outside the battery for

« AnteriorContinuar »