was remarkably black, glossy, and long, and she had a theory of her own on the subject. She believed that the electrical properties depended upon excitability of temperament, or "cat-like" intensity, as she termed it. My more prosaic theory, that it depended simply on the non-conduction or insulating efficiency of long, dry, nonpomaded, glossy hair, was scornfully rejected. She told me that the electrical phenomena were far more brilliant in Canada, during the dry, intense frosts of that climate, than in Edinburgh; that fibres of silk there clung to her fingers, and moved curiously about like spiders' legs.

IN

UNDERGROUND WATERS.

N the chronicle of useful work done under the auspices of the British Association, a prominent place must be given to that connected with the above subject. A report was read at Swansea by that rising young geologist, Mr. C. E. De Rance, in which he describes "the circulation of the underground waters in the Permian, New Red Sandstone, and Jurassic formations of England," and the quality and character of the water supplied to the towns and districts from these formations.

It is quite evident that our present barbarous system of water supply from rivers that receive the sewage of towns and villages is doomed. We must either go to the basin-shaped valleys that receive the unpolluted surface drainage of the mountain slopes and hold them ready for our use in such natural reservoirs as the Bala Lake, the tarns and lakes of Westmoreland and Cumberland, &c., or we must avail ourselves of Nature's filters, the porous rocks, that receive the rain on the faces of their outcrops and carry it under our feet, altered only by the mineral matter it is capable of dissolving out of the rocks themselves.

The situation of the town itself must determine the choice between these sources of supply.

The value of a thorough survey of the underground waters of Great Britain by competent geologists will be understood by reflecting on the following fact.

Our island, and more especially the English portion of it, has somehow been considerably tilted. The stratified rocks of which it is mainly formed do not lie horizontally one above the other, but are so up-tilted northwards that the traveller who runs upon the rail from London to Aberdeen, or from Middlesex to Westmoreland, is, geologically speaking, diving into the crust of the earth. The

rails on which he travels are not laid upon the fair geological surface of the earth, not upon the layers of the earth's crust as they were originally deposited, but upon their up-tipped edges. If a number of books—say music-books-are piled one above the other on a table, their leaves lie horizontally; but if this heap of books is knocked over, so that their backs shall all rest on the table, and their edges lap over each other, these up-tilted edges will rudely represent the position of the up-tipped strata of England, the top book thrown to one end of the table being the S. portion, and the bottom book at the other end the N.

If the up-tipped edges of these books were continuously sprinkled, or exposed to gentle rain, the water would find its way between the leaves, especially if the books had not been pressed, and the leaves were lying loosely on each other.

This is the case with the up-tilted leaves of that great Book of Genesis which the geologist endeavours to interpret. The rain falls on them and sinks through them in varying degrees, according to their porosity. Some are very porous, others almost impermeable. Hence a very great variation in the quantity of underground waters in different districts and at different depths of a given district.

There are differences not only in quantity, but also in the quality of the waters contained in these subterranean reservoirs. The material of some of the strata, whose up-tilted edges are thus receiving the distilled water from the clouds, is to some extent soluble in such water; the material of other strata is practically insoluble. Thus our supposed traveller from London to Aberdeen, on reaching Dunstable, comes upon the edge of one of the series of strata that underlie London, and crop out all around—I mean our familiar chalk, which is such a curiosity to some foreigners. This is very porous, and also soluble in water charged with carbonic acid. Hence the hardness of London spring water that has come through the chalk.

Farther North, out-cropping edges of slate abound. Many of these slates are fairly good water-bearers, but are so nearly insoluble that the water flowing within them is comparatively soft. In other places, as in Derbyshire, South Yorkshire, &c., a coarse, porous sandstone, the "millstone grit," crops out from underneath the coal measures, and receives floods of water that pour out beautifully soft. Wherever this is unmixed, and available, a great saving of soap is effected on account of its softness.

Between these soft waters and the soap-wasting hard waters that ooze through the limestones, are such medium waters as those that so VOL. CCXLIX. NO. 1800.

3 C

abundantly saturate the friable shales of our coal-bearing strata, and which add so much to the cost of working many collieries, on account of the rivulets that must be continually pumped from the pits.

Here and there are strange outbreaks, like the holy well of St. Winfred, where there rush from one hole in the rock about 20 tons of water per minute, forming a river that turns many mills in its short course down to the Dee. The flood bursts upwards, where the porous millstone grit and coal measures suddenly abut upon the nearly impermeable carboniferous limestones that supply the well-known Holywell cements and fluxing lime.

The above hasty sketch of some of the prominent facts, just those that crop up in memory as I write, are sufficient to indicate the useful field that is open for geological research directly bearing upon one of the primary necessaries of life—so necessary, that upon its better and purer supply depend the possible limits of our future increase of population; for if we go on committing joint-stock suicide by supplying one town with the sewage of the next above it, the Malthusian problem will be effectually solved by reaching the limit when typhoid fever will kill a sufficient number to make the death-rate balance that of births.

The work already done by Mr. De Rance, and those associated with him, is but a tentative instalment of the work that should be done, not by the British Association merely, but by the nation, for national prosperity's sake.

We have an admirable organization in the staff of the National Geological Surveyors, and now that they have so nearly completed the first stage of the ordinary Geological Survey, they might at once commence this great and necessary work, which, done as they will do it, if properly supported, would enable any town council or village vestry to know beforehand the quantity and quality of water under its feet, and where and how to find it at depths that shall render sewage pollution impossible.

Some of the existing water companies may pooh-pooh and oppose such researches, but vested interests only maintainable by poisoning our children and sober water-drinking adults are no more worthy of preservation than were those of Messrs. Turpin, Sheppard, & Co., which were assailed, and have been nearly ruined, by the progress of gas lighting and improved police arrangements.

Mr. De Rance estimates the amount of rainfall absorbed by the Triassic Sandstones of Lancashire, Cheshire, and the Midlands to average 400,000 gallons daily for each square mile. The average population of Great Britain is 265 persons per square mile. This

gives above 1,500 gallons daily for each. The supply must of course be concentrated as the population concentrates. In some places a natural concentration of the underground water occurs, and wells may there be sunk, that will draw upon the supplies of several square miles, and thus yield two to three millions of gallons daily.

The artificial concentration is merely a mechanical problem, one of pumps and pipes, the practical solution of which may be safely left to our engineers when the geologists have indicated where the best supply is to be found. The available quantity is probably sufficient to enable us to pick and choose, selecting only the best and softest, and rejecting altogether such as is now supplied to London, and supplied so villainously by the niggardly devices of plug-holes in the roadway, of water-butts and house cisterns, aided, or rather impeded, by the ball-cocks and turn-cocks, that disgrace the great metropolis of the world. I write this in Yorkshire, through which I have been lately wandering, visiting most of its great towns. In none of these have I seen the "F.P. 13 ft., S.C. 15 ft." painted on street walls, nor any such barbarous monster as a turncock to dole out the daily dribble, provided he receives his Christmas box. These towns, and those of Lancashire and the Midlands, like all others where municipal and sanitary civilization is established, are supplied directly and continuously from the public reservoirs.

THE PROGRESS OF THE PHOTOPHONE.

INCE my description of the photophone (see page 628 of last num

SINCE my ofher accounts of experiments of Professor

Bell and Mr. Tainter have been published. From these it appears that the simple form of the instrument which I described is only capable of repeating musical sounds, or variations of pitch, and that something further is demanded to obtain a distinct repetition of articulate speech. This something is the interposition of a film of selenium, having that property of variable conductivity of electricity, with varying degrees of illumination, which I described. Mr. Bell's latest improvement includes a selenium receiver, placed in the focus of a concave mirror, which concentrates the trembling beam of light and all its tremours upon the ingeniously extended selenium film. The variations of the light produce corresponding variations of the power of the selenium receiver to convey a current of electricity, which passes through it from a battery, and these variations of the electric current act upon a pair of telephone receivers, and make them speak, by producing magnetic disturbances similar to those of the ordinary telephone.

At present the instrument is but a philosophical curiosity that has not reached the stage of practical utility, such as the telephone has attained. But we must not be impatient. Long and laborious experimental research may yet be required to perfect it, and this perfection will be attained when a simple diaphragm is devised that will effect distinct articulation without the intervention of the selenium receiver and the battery.

Should this be achieved, the instrument may be used for naval and military communications, and for other cases where there is no intermediate conducting wire such as the telephone requires.

H

ELECTRICITY AND SALTED HERRINGS.

AD any scientific enthusiast of the last generation announced his belief that the progress of electrical science would directly affect the supply of herrings to those inland Catholic countries where they are-when salted-in such demand for food on fast days, his friends would have been anxious concerning his cerebral welfare. As a matter of fact, this is now the case. The Norwegian coast is girdled by 1,200 miles of herring telegraph wire, and telegraph stations are established on the barren rocks of the Lofodden Islands, and in the hollows between the dark precipitous cliffs that form the Arctic face of Europe. Here, among the screaming sea-birds, a watch is kept of the movements of herring shoals, and particulars concerning their progress are flashed to the little settlements of hardy Norsemen who live by the harvest of the Arctic and sub-Arctic ocean. According to such intelligence they make their preparations for securing some of the merchandise that they send so largely to the countries on the Mediterranean.

W. MATTIEU WILLIAMS.