depart furth of this toun the xxiiij day of this instant moneth. Thairfore I pray yow effectuouslie, traist cusing, that ye in the menetyme hald your self constant in my seruice, and aduerteiss your freinds and neighbouris to do the samin and to be in readienes to serue me quhan the occatioun sall offer, as ye haue done trewlie afoir this tyme, speciallie at the last battall, qubair (as I am adwerteist) ye haue done rycht weill your deuoir, ye beand on your featis, quhilk sall nocht be forgit be me in tyme coming. With the help of God I houp to returne agane about the xv day of August nixt, with gud company, for the effect foresaid, God willing. This I beleue ye will do, as my traist is and wes ay in yow. And for to mak ane end of my bill, I will commit yow to the protectioun of the eternall God. At Carlell, the xx day of Maij 1568.

'MARIE R.

'I pray you my lord excuss this stamp, becauss the Quene hes na uchir at this tyme.

'To my Lord Erle of Cassillis.'

To this must be added two other documents of more than ordinary importance, which are here for the first time printed.

It is well known that the marriage of Bothwell to his wife, Lady Jean or Jonet Gordon, was annulled, in order to enable him to contract marriage with the queen, on the ground that no regular dispensation had been obtained so as to enable the first named persons to be united in matrimony by the Church, they being related to each other in the double 'fourth degree of consanguinity;' and it has been held by all historians that this essential dispensation (if it ever existed) had been destroyed. The document itself has now been found in the charter chest of the Duke of Sutherland at Dunrobin. It seems that it remained in the custody of Lady Jean, the repudiated wife of Bothwell, and as she married seven years afterwards, in 1573, Alexander, the eleventh Earl of Sutherland, she took it with her into the repositories of that noble house, where it has passed to her present descendants. The dispensation was granted by John Hamilton, Archbishop of St. Andrews, and Legate of the Pope, in full ecclesiastical form. It follows, therefore, from the discovery of this instrument, that the marriage of Bothwell to Lady Jean Gordon was perfectly legal and canonical, and that the grounds on which it was dissolved were false. That being the case, his subsequent marriage with the queen was no marriage at all, but an adulterous connexion between two persons, both previously married, who procured their freedom by the murder of the husband of the one, and the betrayal of the wife of the other. The discovery of the dispensation completes the evidence of the inexpressible turpitude and guilt of the whole

transaction. Its existence was first noticed by Dr. John Stuart in the second Report of the Commissioners for Historical Manuscripts in the year 1871. Lady Jean Gordon long survived all these events, and died in the year 1629 at the age of eighty-four. It is curious that the wife of Bothwell should have lived far into the reign of Charles I.

Another remarkable document, now printed apparently for the first time, is the revocation by Mary Queen of Scots of her resignation of the crown of Scotland in favour of her son. This instrument was drawn up in 1568, but the copy existing in the charter chest of the Earl of Haddington is not dated or signed. It consists of a vigorous and voluminous denunciation of the traitors who caused this monstrous and unnaturall defection and revolt of our detestabill subjects,' especially James, callit Erle Morray, quhome we of ane spurious 'bastard (althocht namit our brother) promovit fra ane religious monk to Erle and Lord,' &c., and constitutes James, Duke of Chatelherault, the universal and only protector, regent, and governor of the realm. The whole document is extremely curious, for it contains, in language more vituperative than judicial, the whole of Mary's case against her enemies; but it is far too long to be quoted in this place.

We now take leave of Mr. Fraser by offering him our thanks for the instruction and amusement he has afforded us, and we hope that he will long continue this series of portly volumes; the more so, as we have heard that he is now engaged in examining the papers of the great house of Scott of Buccleuch, which cannot fail to be of uncommon interest, especially in regard of the events of the seventeenth century.

ART. II.--Electric Lighting. A Practical Treatise. By HIPPOLYTE FONTAINE. Translated from the French by PAGET HIGGS, LL.D., Assoc. Inst. C. E. London: 1878.

IT T is not unusual, at the present time, for even scientific authorities to allude to the spark which Faraday was the first to produce while experimenting with his magnets, as the germinal gleam of that electric light, which now attracts the admiring eyes of so large a number of observers. Electric illumination can nevertheless claim an older pedigree. The Voltaic Arc, with its even yet unsurpassed splendour, was nearly of adult years, and already in a state of virile strength, when Faraday's magnets and coils began their revolutionary career. Sir Humphry Davy was working with

a Voltaic Arc produced by a battery of some two thousand pairs of plates as early as 1813. The experiments of Faraday with the electric currents produced by moving magnets began in 1830.

But even the Voltaic Arc can hardly be correctly spoken of as the first electric light exhibited to human eyes. Electric illumination in its most stupendous and grandly developed form was presented in the spontaneous operations of nature, not only before Volta had constructed his pile, but even before science had dawned upon the intellect of man. When the storm-cloud flashes its dazzling gleam into the darkness of night, it is, in strict reality, the electric light which illuminates the sky. The lightning from nature's storm-cloud battery is, indeed, more vivid and beautiful than any flash which artificial arrangements made by human hands have yet been able to develope. But it is an obvious defect in nature's own process for the production of this light, that the flash endures for such a brief moment of time. The illumination of the lightning continues, at its best, for only the two-thousandth part of a second. Before lightning could be turned to account as a continuous light, there would, therefore, have to be flashings from the storm-cloud amounting to as much as four million discharges per hour. Human audacity has not yet dreamed of accomplishing any such stupendous task as the fusion of fitful lightnings into enduring and useful light. But such nevertheless is the direction in which the electrician of the day is attacking the problem with his miniature evolution of the resplendent meteor. The Gramme and Siemens machines pour out their unceasing streams of miniature lightning in such rapid succession that the eye cannot detect the intervals which separate the consecutive flashes.

Lightning is in all essential particulars the same thing as the sparks which are evolved by the revolutions of magneto-electric machines. Its light is entirely due to the raising of a track of material molecules, along the route through which the electric discharge takes its way, into a condition of shining brightness. The electric force gathers to itself these molecules as food for its fires, as it bursts through the broad chasms of air that lie in its path. The line of light is in reality a closely packed chain of shining sparks. The material which thus shines is not of necessity in a burning state in the ordinary sense of the word. It shines only on account of the intensity of the vibratile movement into which the constituent molecules are thrown by the shock of the electrical discharge. Its state is that which is technically distinguished as incandescence; its particles are

simply glowing with radiant heat-glittering with an emitted splendour that is not in any sense dependent upon the chemical influence of oxygen. The light is most effective and brilliant, indeed, when there is no combustion whatever in the case, and when the illumination is entirely due to the radiant glow set up by the vibratile energy.

The lightning of the thunder-cloud assumes various tints, as most people are aware. It is sometimes of a lilac hue, sometimes orange, and sometimes pink or rose-coloured. Sometimes it has the gleam of shining lead, and sometimes the pure whiteness of burnished silver. These diversified colours are more strikingly exhibited in tropical regions than in temperate climates. But their peculiarity is, in every case, due to the nature of the vaporous substances which are at the time floating in the air, and which are made to glow on the passage of the electrical discharge. The molecules of some substances shine, when they are raised to incandescence, with a lilac light, of some with an orange, and of some with a red or with a pure white sheen. The spectroscope, in the hands of a skilful observer, now in most cases detects the exact nature of the substance which is made to glow. The most brilliant effects in atmospheric lightning are produced when there is metallic dust of some kind in the track of the meteor. There are some wonderful instances on record of the freaks which lightning will play in gathering up to itself the metallic pabulum of its fires, such as the one alluded to by Constantini, in which, in the year 1749, a golden bracelet was taken by a flash of lightning from the arm of a lady, who was closing a casement during a storm, without inflicting upon her any very serious harm. M. Fusinieri points out that there are at all times ample stores of vaporised iron, sulphur, and carbon present in the air for the service of the lightning, and that it is these which are seized upon and transported along the track of the discharge as a stream of incandescent particles.

For the production of the electric light in the artificial and manageable form which the enterprise of the electrical engineer now contemplates, there must of necessity be a sustained current or stream of the mysterious agent which is spoken of as electricity, transmitted through an easy channel of some good conducting substance, and a break or gap in that channel where the light is required to appear. There must be what the electrician terms a closed circuit of the moving force, with an abrupt and narrow interruption of its continuity in one particular spot. The luminous effect is in reality evolved where the electrical force has to gather up its energies to over

leap the obstacle which is designedly laid across its path. The light is the visible manifestation of the accumulated effort called up to overleap the gap. This bearing of the matter is very well illustrated in the well-known arrangement in which a Leyden jar is discharged through a light steel chain stretched from the outer coating to the knob. At the instant of the discharge a bright spark presents itself between all the contiguous links of the chain. Each spark at that instant only appears where the electrical force has to burst through the air-space, or gap, which intervenes between link and link. The breaks in the chain interpose chasms of resistance in the course of the discharge. At each chasm where the resistance occurs the impeded force collects its energies to meet the emergency, and, as it does so, leaps into light.

In the beautiful effect known as the Voltaic Arc, first developed upon a grand scale by Sir Humphry Davy under the opportunities which the costly batteries of the Royal Institution placed at his command, the electrical current is produced by the instrumentality of a galvanic arrangement of plates and cells, and it flows through the copper wire which is provided for its transmission, from one terminal plate, or pole, of the battery round to the opposite terminal plate. So long as the opposite terminals of the battery are connected in this way, successive streams, or currents, continue to chase each other in rapid succession through the wire. The force is in the first instance generated by a consumption of some one or more of the elements of which the battery is composed. In the earliest form of the galvanic cell, where plates of zinc were ployed for the development of the current, the effect was attended by, and to a considerable extent due to, an actual combustion of the zinc, set up and maintained by the acid menstruum in which it was plunged. The electrical force which streamed through the wire was as essentially a product of this consumption of the zinc and liquid menstruum as heat is the product of the consumption of coal when it is burned in a furnace.

In the early experiments of Davy, the break in the circuit, at which the light was made to present itself as a luminous arc, was effected by dividing the copper wire at some convenient midway part, and by arming each end of the broken part with a piece of pointed charcoal. When the luminous arc was to be produced, the two points of charcoal were in the first instance pressed gently together. The circuit for the transmission of the current was in that way made complete, the current began to flow, and a bright spark appeared where