and while we were on the lake the heavens again darkened, and the deck was flooded by the gushing rain. The dusky cloud-curtain was rent at intervals, and through the apertures thus formed parallel bars of extraordinary radiance escaped across the lake. On reaching Interlaken I drove to the steamer on the lake of Brientz. We started at 6 P.M., with a purified atmosphere, and passed through scenes of serene beauty in the tranquil evening light. The bridge of Brientz had been carried away by the floods, the mail was intercepted, and I joined a young Oxford man in a vehicle to Meyringen. The west wind again filled the atmosphere with gloom, and after supper I spent an hour watching the lightning thrilling behind the clouds. The darkness was intense, and the intermittent glare corespondingly impressive. Sometimes the lightning seemed to burst, like a fireball, midway between the horizon and the zenith, spreading a vast glory behind the clouds and revealing all their outlines. In front of me was a craggy summit, which indulged in intermittent shots of thunder; sharp, dry, and sudden, with scarcely an echo to soften them off.

65

NOTE ON THE SOUND OF AGITATED WATER.

A LIQUID vein descending through a round hole in the bottom of a tin vessel exhibits two distinct portions, the one steady and limpid, the other unsteady and apparently turbid. The flash of an electric spark in a dark room instantly resolves the turbid portion into isolated drops. Experiments made in 1849 with such a jet directed my attention to the origin of the sound of agitated water. When the smoke is projected from the lips of a tobaccosmoker, a little explosion usually occurs, which is chiefly due to the sudden bursting of the film of saliva connecting both lips. An inflated bladder bursts with an explosion as loud as a pistol-shot. Sound to some extent always accompanies the sudden liberation of compressed air, and this fact is also exhibited in the deportment of a waterjet. If the surface of water into which the jet falls intersect its limpid portion, the jet enters silently, and no bubbles are produced. If the surface cut the turbid portion of the jet, bubbles make their appearance with an accompaniment of sound. The very nature of the sound pronounces its origin to be the bursting of the bubbles; and to the same cause the murmur of streams and the sound of breakers appear to be almost exclusively due. The impact of water against water is a comparatively subordinate cause of the sound, and could never of itself occasion the 'bubble' of a brook or the musical roar of the ocean.-Philosophical Magazine, February 1857.

F

VI.

THE URBACHTHAL AND GAULI GLACIER.

OUR bivouac at Meyringen was le Sauvage, who discharged his duty as a host with credit to himself and with satisfaction to us. Forster (the statesman) arrived, and in the afternoon of the 3rd we walked up the valley, with the view of spending the night at Hof. Between Meyringen and Hof, the vale of Hasli is crossed by a transverse ridge called the Kirchet, and the barrier is at one place split through, forming a deep chasm with vertical sides through which plunges the river Aar. The chasm is called the Finsteraarschlucht, and by the ready hypothesis of an earthquake its formation has been explained. Man longs for causes, and the weaker minds, unable to restrain their longing, often barter, for the most sorry theoretic pottage, the truth which patient enquiry would make their own. This proneness of the human mind to jump to conclusions, and thus shirk the labour of real investigation, is a most mischievous tendency. We complain of the contempt with which practical men regard theory, and,

to confound them, triumphantly exhibit the speculative achievements of master minds. But the practical man, though puzzled, remains unconvinced; and why? Simply because nine out of ten of the theories with which he is acquainted are deserving of nothing better than contempt. Our master minds built their theoretic edifices upon the rock of fact, the quantity of fact necessary to enable them to divine the law being a measure of individual genius, and not a test of philosophic system.1

The level plain of Hof lies above the mound of the Kirchet; how was this flat formed? Is it not composed of the sediment of a lake? Did not the Kirchet form the dam of this lake, a stream issuing from the latter and falling over the dam? And as the sea-waves find a weak point in the cliffs against which they dash, and gradually eat their way so as to form caverns with high vertical sides, as at the Land's End, a joint or fault or some other accidental weakness determining their line of action; so also a mountain torrent rushing for ages over the same dam would be sure to cut itself a channel. The lake after its drainage left the basis of green meadows as sediment behind; and through these meadows now flows the stream of the Aar. Imagination is

This was written soon after Mr. Buckle's Royal Institution lecture, which I thought a piece of astonishing rhetoric, but of very unsound science.

essential to the natural philosopher, but its matter must be facts; and its function the discernment of their connection.

We were called at 4 A.M., an hour later than we intended, and the sight of the cloudless mountains was an inspiration to us all. At 5.30 A.M. we were off, crossing the valley of Hof, which was hugged round its margin by a light and silky mist. We ascended a spur which separated us from the Urbachthal, through which our route lay. The Aar for a time babbled in the distance, until, on turning a corner, its voice was suddenly quenched by the louder music of the Urbach, rendered mellow and voluminous by the resonance of the chasm into which the torrent leaped. The sun was already strong. His yellow light glimmered from the fresh green leaves; it smote with glory the boles and the plumes of the pines; soft shadows fell from shrub and rock upon the pastures; snow-peaks were in sight, cliffy summits also, without snow or verdure, but in many cases buttressed by slopes of soil which bore a shaggy growth of trees. To the right of us rose the bare cliffs of the Engelhörner, broken at the top into claw-shaped masses which were turned, as if in spite, against the serene heaven. Bennen walked on in front, a mass of organised force, silent, but emitting at times a whistle which sounded like the piping of a lost chamois. In a hollow of the