detected by my colleague, Mr Skae, in Nithsdale, at a height of 1250 feet above the sea." 8. Lastly, may I be permitted, as there is still a wide field for farther investigation, to express a hope that the Boulder Committee may be re-appointed, and with additional labourers to carry on the work. I will be happy to be allowed to remain on the Committee, but I wish to resign the honour of being Convener. I begin to find that I am now not able for the hill-climbing and trudging across Highland moors and morasses, which boulder-hunting requires. Edinburgh, 24th May 1878. At a Meeting held this day, the Council re-appointed the Boulder Committee, with the addition of Dr Andrew Fleming, M.D.; William Jolly, Inspector of Schools, Inverness; and Ralph Richardson, Secretary of the Edinburgh Geological Society; and agreed to express a hope, that Mr Milne Home would continue Convener of the Committee. The Council further agreed, that the "Remarks" by Mr Milne Home, at the Society's meeting on the 20th inst., when he presented the Committee's Fourth Report, appear in the Society's Proceedings, along with the Report. J. H. BALFOUR, Secretary. The Boulder Committee now consists of the following Fellows: Sir Robert Christison, Bart. Sir Charles Wyville Thomson. Rev. Thomas Brown, Edinburgh. Dr Andrew Fleming, M.D., Edinburgh. William Jolly, Inverness. Dr Arthur Mitchell, M.D., Edinburgh. Professor Nicol, Aberdeen. Ralph Richardson, Edinburgh. Thomas Stevenson, C.E., Edinburgh. David Milne Home, LL.D. (Convener). Monday, 3d June 1878. SIR C. WYVILLE THOMSON, Vice-President, in the Chair. The following Communications were read: 1. On the Splitting up of Electric Currents, as detected by the Telephone, and the founding thereon of a Sounder to call attention from one Telephone to another. By R. H. Bow, C.E. The telephone is of no use as a "far-speaker," without some means of calling the attention of the attendant at the distant station. Nothing could well be better than the "electric-bell call," and the sounder which I am about to describe makes no pretensions of competing with the bell, except on the points of simplicity, cheapness, and facility of use; and although its employment is limited to short length lines, it may be assumed that it is upon short length lines that the telephone will be most frequently used. I have had this sounder in experimental use for more than three months, and have shown it to many persons as a very obvious expedient. However, as it does not appear to have been referred to in any publication, I venture to bring it as a Note before the Society; it is of too trifling a nature to be made the subject of a formal paper. In any of the sounders I have seen described, the battery, or other source of electrical excitement, has been placed in simple circuit with the pair of telephones, or put into circuit with the distant one. In the proposed method of sounding, by means of a galvanic battery, the battery is kept separate, and, when used, the short wire from the one electrode is rested against one of the wires of the telephone, while the wire from the other electrode is slid with a very gentle vibrating touch upon the other wire leading from the telephone. On the well-known principle of derived currents, we know that the greater portion of the electricity will pass through the shorter or less resisting circuit of the nearer telephone, and yet that there will be a not inconsiderable portion diverted to travel round by the distant one; and this, if the distance be not very great, and the telephones be of suitable construction, will suffice to elicit sufficient noise at the distant station to call the attention of any one in the same or even an adjoining apartment; the noise given out by the distant telephone will not be altogether due to this diverted current, but will owe part of its volume of sound to telephonic sympathy with the great agitation produced in the one near the operator. Before entering into any details as to the construction of telephones best suited for this mode of sounding a "call," and for short distances, permit me to describe two experiments upon the detection of derived currents by means of the telephone. Fig. 1 represents a wire of about 320 feet in length, bent so as to bring the middle of its length near to the telephone T, to which its extremities are attached; G is a battery of one cell, and A and B the wires from its electrodes; one of these, A, is fixed to the long wire at a; the other, B, is movable at b, the point b being taken at different distances from u. When the length of a-b is taken equal to from 3 to 4 feet, the noise emitted by the telephone might be sufficient to act as a call, although only about 1 per cent. of the current from the battery can then pass through the telephone; when the length of a-b is reduced to 1 foot, the sound from the telephone may yet be heard several feet away, and as the distance of a-b is decreased, the telephone must be brought nearer and nearer to the ear in order to hear the crepitating sound; with a-b equal to 3 inches, it may be heard 3 inches off; and when the telephone is held against the ear the distance of a-b may usually be reduced to less than a quarter of an inch before the sound is lost. Now, when the length of a-b is one quarter of an inch, the strength of the diverted current passing through the telephone used would only amount to the one twenty-thousandth (2000) of that circulating through the battery. But I have now to note a very puzzling circumstance. Sometimes, under conditions I have not been able to determine, the crepitating sound was found not to cease even when b and a were brought together, but continued to be heard when the one wire, B, was moved upon the other A, at c. Here there can be no dynamic current produced in the long wire. I shall not detain you with my speculations on the subject; but I should mention that the wire was very imperfectly insulated. The second experiment gives an interesting practical example of the interference of one pair of telephones with another pair, due to the splitting up of currents. The rough diagram, fig. 2, will serve to explain the arrangement. A and A' constitute one pair of tele phones, the single connecting wire measuring 60 feet; B and B' are another pair of telephones-these are connected by a copper wire 270 feet long; for the return currents the gas pipes and earth are employed. The gas pipes are indicated by dotted lines; M and M' are gas metres belonging to different houses; and P and P' are the gas mains in different streets, and at a direct distance apart of about 400 feet. It will be observed that the gas pipe from C to M is common to the two circuits. Now, it was soon noticed that when the battery-sounder was made use of at A, it caused a sounding not only in A', as intended, but also in B, sufficiently loud to be heard several yards off if attentively listened for. This noise was, of course, due to a derived current splitting off at C, and making the long circuit round by B, B', M', possibly to the gas main P', and thence to P and back by M, where it rejoins the principal current on its way to A. And using the battery at any one of the telephones causes more or less noise in all the four. But the small amount of sound produced by such straying currents is not likely to cause confusion. The Telephones used with the Battery-Sounder. If it were attempted to use the sounder in combination with telephones constructed in accordance with Professor Bell's instructions—that is, VOL. IX. 5 A having coils so long as 180 feet of wire so thin as No. 36-comparative failure would result from the very great resistance offered We must try to do with coils offering an insignifi to the current. cant amount of resistance. I find that the mode of arranging the parts of the telephone has a great influence on the efficiency, and the construction I have found up to the present time to be the best is as follows:-Taking a 3-inch horse-shoe magnet, I break off about half an inch from one leg; the nick made to indicate the north end is usually at about this distance from the extremity, and the breaking of it there is an easy operation. I then round the unbroken end on a grindstone, and next gum a strip of thin paper round that leg, and upon the paper coil the desired length of silk-covered wire. Taking next a piece of wood 4 × 4 inches or 4 x 5 inches, and half an inch thick, a hole 2 inches in diameter is cut cleanly through it, and crossing the hole is fixed, in letter T fashion, another piece of wood 4 x 3 inches; on this latter piece the magnet is laid with its south or coil-covered end projecting centrally into the hole, and it is fixed down by one screw passing through a small cross piece of wood placed above it. This admits of after-adjustments being very readily made. The ferrotype plate, 21 inches in diameter, is laid as a cover over the outer aspect of the 2-inch hole, and secured there by the usual ring of wood which constitutes the ear or mouth piece. With such an instrument placed at A, fig. 2, and another telephone at A', I have experimented on the length of coil needed. Four or five feet of wire gave very satisfactory results, speaking being heard distinctly, and with sufficient loudness. I then tried shorter and shorter lengths, and found the volume of sound to become reduced certainly, but in a surprisingly small degree; and at last I carried the shortening so far, that only 4 inches remained as a coil, and though the sound with this fragment was much reduced, giving the voice a far-away character, conversation could still be carried on. I did not think it necessary to push the reduction further, having become convinced that no very great length of wire was needed for the coil to secure distinct hearing, at least for short lines, say of quarter of a mile or less. And for the present I have adopted a length of 9 feet of No. 28 wire (weighing 6 grains per foot length) as a satisfactory coil, presenting a resistance of only |