152 Advertisements. {CHEMICAL NEWS, April 4, 1879. INSTITUTE OF CHEMISTRY OF GREAT BRITAIN Caswell, Charles Benjamin, F.C.S., 13, George-road, Birmingham John Attfield, Ph.D., F.C.S. James Bell, F.C.S. Dugald Campbell, F.C.S. Warren e la Rue, D.C.L., F.R.S. David How rd, F C.S. E. J. Mills, D.Sc., F.R.S. Thomas Stevenson, M.D., F.C.S. This Institute was established in 1977 to ensure that Consulting and Analytical Chemists are duly qualified for the proper discharge of the duties they undertake by a tuorough stady of Chemistry and allied branches of Sci nce in their application to the Arts, Public Health, Agricu.ture, and Technical ILdu try. NAMES of FELLOWS. Abel, F.A, C. B., F.R.S., F.C.S., Royal Arsenal, Woolwich, S.E. Acwort., Joseph J., F.C.S., Oakvil e-house, Gravesend Aitkin, Andr w P., D sc., Edinburgu University Alldred, C.H., F.C.S., 37, Mincing-lane, E.C. Allen, Alfred H., F.C 8., 2, oll-giate-crescent, Sheffield Amstrong, H. E., Ph.D., F.R.S., F.C.S., London Institution, E.C. Baynes, James. jun., F.C 8., Kingston-upon Hull Bean, Charie Edward, F.C.S., Brooklyn-house, Shepherd's-bush, W. Beilby, George, Midcalder, scotland Bell, J. Carter, F.C.S., Assoc. R.S M., Kersal Clough, Higher Broughton, Manchester Bell, Jaunes, F.C.., Laboratory, Somerset-house, W.C. Bell, William Gomm, Assoc. R.S.M., 5, Duchess-road, Birmingham Bickerdike, William Edward, F.C.S., Surbiton-place Blackourn Bickerton, Professor A. W., Christchurch, New Zea and Bischof, Pofessor Gustav, F.C.S., 4, Hart-street, Bloomsbury, W.c. Bowdler, Arthur Clegg 20. Wellington-str. et, Blackburn Brazier, Professor James Smith F.C.S., University, Aberdeen Brooie, Sir Benjamin C., F.R.S., F.C.S., Brockham Warren, Surrey Brown, Adrian John, F.C.S., Burton-on-Trent Brown, Edwin Ormond, F.C.S., Royal Arsenal, Woolwich, S.E. Bruce, A.C., M.A., F.C.S., King Edward school, Birmingham Cameron, Charles A., M.D., F R.S.C.I., 15, Pembroke-road, Dublin. Cammack, John, 50, Pecker's-hill, Sutton, near St. Helen's Carteig he, Michael, F.C.S., 180, New Bond-stre.t, W. Church, Professor A. H., F.C.S., Agricultural College, Cirencester Clapha, Robert C lvert, F.C.S., Ears on, near Newcastle-on-line. Clark John, Ph.D., F.C.S. 138, Bath-street, Glasgow Claudet, F. F.C S., 6 and 7, Cole man-street, E.C. Cleaver, Edward Lawrence, F.C.S., 289a, King's-road, S. W. Cloud, Thomas Charles, Assoc. R.S.M., Walla oo, South Australia Corfield, Professor W. H., M.A., M.B., F.C.S., 10, Bolton-row, Mayfair, W. Cownley, Alfred John, F.C.S., 106, Fenchurch-street, E.C. Crowder, William, 28, Evering-v.lias, Evering-road, U. per Clapton, E Dalziel, John Graham, United College, St. Andrew's, N.B. Darby, Steph. n, F.C.S., 140, Leaden all-street Darling, William Howarth, F.C.S., 126, Oxford-street, Manchest r Davies, R. Higgins, F.C.S., 6, Bradmore-park-terrace, Goldbawkroad, W. Davis, G. E., F.C.S., Dagmar-villa, Heaton Chapel, near Stockport Deacon, Henry Wade, Appleton-house, Widnes De Chaum nt, Francis, M.D., Army Medical schoo', Netley De la R, Warren, D.C.L., F.R.S., F.C.S., 73, Portland-place, W. Dent, William Y., F.C.S., Royal Arsenal, Woolwich, S.E. Dewar, Professor James, F.R.8., Cambridge Dittmar, Professor W., Anderson's College, Glasgow Divers, Professor E., M.D., F.C.S., Yokohama, Japan Dixon, William A., F.C.S., Chemical Laboratory, School of Arts, 8ydney Dodd, Thomas Henry, F.C.S., Royal Arsenal, Woolwich, S.E. Dougal, Samuel S., Glenpark-villa, Busby, near Glasgow Downar, George Frederick, Workington reyfus, Charles, 7, Chapel-walks, Manchester Duncan, James, F.C.S., 71, Cromwe l-road, S. W. Dupre, Auguste, Ph.D., F.R.S., Westminster Hospital, S.W. Ea ly, William, Trinity College, Dublin Eltoft, Thomas, F.C.S., 55, Torriano-avenue, Camden-road, N. Estcourt, Charles, F.C.S., St. James's-square, Manchester Evershed, Frank, 8, Dalrymple-terrace, Glenarm-road, Clapton, E. Fairley, Tomas, F.R.S.E., F.C.S., 16, East-par de, Leeds Farries, Thomas, F.C.S., 16, Coleman-stre t, E.C. Fenton. Henry J. H., Christ's College. C mbri ge Ferguson, Professor John, M.A., F.CS., University, Glasgow Field, Frederick, F.R.S., F.C.S. Hither-green-lodge, Lewisham, 8. E. Fletcher, Alfred, 5, Edge- ane, Liverpool Foord, George, F.C.S., R yal Mint, Melbourne Foster, William, B.A., F.C.S., Middlesex Hospital. W. Frankland, Professor E., D.C.L.. F.R.S., F.C.S., Royal College of Friswell, R. J., F.C S., 10, Clapton-square, E. Fuller, W. J., F.C.S., Corve-lodg, Greenway-road, Redland, Bristo Gale, Samuel, F.C.S., 338, Oxford Street, W. Galloway, Professor Robert, F.C.S., M.R.I.A., Royal College of Gardner, John, F.C.S., 11, St. Paul's-crescent, Camden-square, N. Gib rt, John Henry, Ph.D., F.R.S., F.C.S., Harpenden, St. Alban's Glover, G. T., F.C.S., 30, Donegall-place, Blfast Gordon, Joseph Gordon, F.C.S., 20, King-street, S.W. Gore, George, LL.D., F R.S., Islington-row, Edgbastor, Birmingham Gro-jean, B. J., F.C.S., Messrs. Lowes' Chemical Works, Millwall, E. Hake, Henry Wilson, Ph.D., F.C.S., Carlton-chamberɛ, 12, Regentstreet, W. Halse, William Edward, F.C.3., 21, Mincing-lane, E.C. Harkness, Wiliam, F.C.S., Laboratory, Somerset-house, W.C. Hartley, W. Noel, F.R.S.E., F.C.S., King's Coll, ge, W.C. Hastings, H. Mitchell F., 16, Vicarage-garde s, Kensington, W. Hehner, Otto, F.C.S., 54, Holborn Viaduct, E.C. Helm, H nry James, F.C.S., Laboratory, Somerset-house, W.C. NEWS Biggin, James, F.C.3., Woodhey, Kersal, Manchester Hill, Alfred, M.D., F.C.S., Birmingham Hills, Thomas Hyde, F.C S., 338, Uxford-street, W. Hodges, Frederick, Queen's College, Belfast Hodges, John Freder ck, M.D., F.C.S., Queen's College, Belfast Hopwood, George Ma ley, F.C.S., Mining De artment, Melbourne Howard, David, F.C.S., Rectory House, Walthamstow, E., and Stratford, E. Howard, Thomas, F.C.S., 52, Swinton-street, Gray's-inc-road Hugues, John, 79, Mark-lane, E.C. Huntingdon, Alfred Kirby, A soc. R.S.M., Abbeville-house, Green-hill, Hampstead, N. Hurter, Ferdinand, Ph.D., Widnes. Huskisson, Henry Owen, F.C.S., 42, Highbury-park, N. Hus n, Charles William, B.Sc. (Lond.), 5, York-buildings, Dale-street, Liverpool Hutchings, William Maynard, Rock Les, Mount Pleasan:-road, Huxley, J. H., Assoc. R.S.M, Crescent road, Sharrow, Sheffield Jarmain, George, F.C.S., 84, Northgate, Huddersfield Johnsen, George, Sulling fleet, F.C.S., I., Savile-row, W. Joe. E, W. T., F.C.S., Wolverhampton Jones, Francis, F.R.S.E., F.C.S., Grammer School, Manchester Keene, James Boddely, 38, Hartham-road, Camden-road, N. Kellner, William, Ph.D., F.C.S., Royal Arsenal, Woolwich, S.E. Kinch, Edward, F.C.S., Tok o Japan Kig, John Falconer, F.C.S., Edinburgh Kingzett, Charles T., F.C.S., 12, Aurol-road, The Cedars Estate, West Kitcuin Arenibald, F.C S.. 27, King-street, Whitehaven Lawes, John Bennet, F.R.S., F C.S., Rothamstead, St. Albans Lawson George, LL.D., Dalhousie College, Halifax, Nova Scotia, Leebody, Professor John Robinson, M.A., Magee College, Londonderry Liveing, Professor George Downing, M.A., F.C.S., Cambridge Lott, Frank Edward, A-soc. R.S.M., Soapenbill, Burton-on-Trent Lowe, William Foulkes, F.C.S., Assoc. R.8.M., Hough-green, Chester Lyte, Farnuam Maxwell, F C.8., Cotford, Oakhill-road, Putney, S.W. Macadam, Stevenson, Ph. D., F.R.S.E., F.C.S.. Edinburgh Macar, James, r.C.S., St. Rollox, Glasgow Max n, George Hogarth, F.C.S.. Walton-on-Thames Marcet, Will am. M.D., F.R.S., F.C.S., Athenæum Club, London, W. Marreco, Professor A. F., F.C.S., College of Physical Science, Newcastle-on-Tyne Maskelyne, Nevil Story, F.R.S., F.C.S., 112, Gloucester-terrace, W. MeL od, Professor Herbe t, F.C.S., Cooper's-bill, Staines Mills, rofessor Edmund J., D.Sc., F.R.S., F.C.S., Anderson's College, Mona, Ludwig, F.C.S., Winnington-hall, Northwich Morfit, Campbell, Ph.D., F.C.S., 16, Harley-road, South Hampstead, N.W. Mo gan, Thomas M., Victoria College, Jersey Moss, John, F.C.S., 300 High Holoorn, W.Č. Morriso, Robert Milner, D Sc., 13, Douglas-crescent, Edinburgh Mu ler, Hugo, P.D, F.R.8., F.C.S., 110, Bunhid-row, E.C. Newlands, John A. R., F.C.S. 18, Josephine-ave. ue, Brixton-rise, S.W. Nicholson, E. hambers, F.R. F.C.S., Carlton-house, Herne-hill Nicho son, Edward, A.M.D., F.C.S. St. Tho Las Mouut, Madras Nickels, Benjamin, F.C.S., Sudbury, Harrow Odling, Professor W., M.B., F.R.S., F.C.8., 15, Norham-gardens, Oxford Oding, Walter, F.C.S., Burton-on-Trent Ogilvie, Thoma R bertson, F.C.S., B nk-top. Lyle-street, Greenock Ogston, George Henry, F C.S., 9, De hay-street, Westminster, S. W. O'Sullivan, Cornelius, F.C.S., 140, High-street, Burton-on-Trent Parkinson, Robert, Ph.D., Bradford Patterson, Thomas Law, F.C.S., Belmont, Margaret-street, Greenock Pattinson, John, F.C.S., 75, The side, Newcastle-on-Tyne Pearce, Walter, Maidenhead Pedler, Professor Alexander, F.C.S., Presidency College, Calcutta Price, Astley Past n, Ph.D., FC.8, 47, Lincoln's-inn-fields, W.C. Ramsey, William, Ph.D., F.C S., 11, Ashton-terrace, Glasgow Reyi olds, Professor J. Emorou, M.D., F.C.S., Trinity College, Dublin R ley, Edward, F.C.s. 148, Finsbury-square, E.C. Rimmington, G orge, 9, Bridge-street, Bradford Roberts, Thomas, 4, Alfred road, Handsworth, near Birmingham Robinson, George Carr, F.R.S.E., Laboratory, University, Edinburgh Kocnod, Heinrich, Micdiesboro-on-Tees Kodwell, George Farrer, F.C.S., Mariborough College Ronalds, Eamuna, Ph.D., F.R S.E., Bonnington-house, Edinburgh Roscoe, Professor Heary E, Ph.D., F.R.S., F.C.S., Owen's College, Manchester Rosenthal Gustav, Ph.D., Wandsworth-bridge-wharf, Fulham, S.W. Russell, Will.am James, Ph.D., F.n.S., F.C.S., St. Bartholomew's Hospital, E.. Ryan, Dennis, The School of Medicine, Liverpool Salter Mortyn John, F.C.S., 12, Forest-road, Daiston, N. schunck, Edward, Ph.D., F.R S., F. S., Kersall, near Manchester Sen er Alfred, M.D., F.C.S., 12 Brownswood-vilias, Finsbury-park,N. S ebold, Louis, F.C.S., Oxford-street, Manchester Siemens, C. William, D. .L., FR.S., F.C.S., 12, Queen Anne's-gate, Smith, J. Denham, F.C.S., Fairlawn, Coombe-wood, Kingston-on- Smith, Robert Angus, Ph.D., F.R.S., F.C.S., 22, Devonshire-street Manchester Smith, Watson, F.C.S., Wilmslow, near Manchester nelus, George James, F.C.S., Assoc. R.S.M. Workington Spiller, John, F.C.S., 2, St. Mary's-road, Canonbury, N. Stenhouse, J., 1L.D., F.R.S., F.C.S., 17, Rodney-street, Pentonville, N. Steuart, Daniel Rankin, Broxburn, Scotland Stevenson, James Cochran, M.P., F.C.S., Westoe, South Shields Stewart, A Young, F.C.S., Apotheca ies' Hail, Bla k riars, E.C. Swan, Joseph Wilson, F.C.S., Newcastle-on-Tyne Szczepanowski, Stanislas A. Prus., F.C.S., 6, Stafford-place, Buckingham-gate, ».W. Tate, Alexander Norman, 7 and 9, Hackins Hey, Liverpool Taylor, James, F.Ć.S., Farmers' Club, Inns of Court Hotel, Holborn, E.C. Tomlinson, Charles, F.R.S., F.C.S., 3, Ridgmount-terrace, Highgate Tucker, Alexander E., Lawn-terrace, Rhymney, South Wales Versmann, Frederick, Ph.D., 15, Trinity-square, Great Tower-street, E.C. Viccajce, K. R., 10, Churney-road, Pombay Vincent, Charles, W., F.R.S. E., F.C.S., Royal Institution, Albemarlestreet, W., and 23, Harvest road, Holloway, N. Voelcker, A. Ph.D., F.R S., 39, Argyle-road, Kensington, W. Walker, John Francis, M.A., F.C.S., Sidney Suss.x College, Cambridge, and 16 Gllygate. York Wallace, Willian, Ph.., F.R.S.E., 138, Bath-street, Glasgow. Watt, Alexander, F.C.S., 24, Thackery-street, Liverpool Watson, David, D.Sc., F.C.S., Assoc. R.S.M., Broughton Copper Watts, John, D.Sc., F.C.S, University Laboratory, Oxford Wils, Thomas, F.C.S., Royal Naval College, Greenwich. S.E. CHEMICAL NEWS, April 4, 1879. The each for the two best original investigations involving Gas Analysis. These Prizes will be open to Associates, and to all nonFellows of the Institute who shall before the 31st December next have qualified for the Associateship in all respects short of passing the piescribed practical examination, and successful competition for these prizes will be accepted in lieu of such practical examination.-Further information may be obtained on application to the Secretary, Mr. C. E. GROVES, Somerset House Terrace, W.C. THE MIDDLESEX HOSPITAL MEDICAL SCHOOL-SUMMER SESSION, 1879. Lectures and Clinical Instruction will commence on Thursday May 1-For Prospectus with full details apply to the Dean or the Resident Medical Officer at the Hospital. The Prestolee Alkali Works, Farnworth, near Bolton, Lancashire, fitted with costly Plant, Machinery, and Apparatus for the Manufacture of Soda-ash, Bleaching-powder and Liquor, and Sulphuric Acid, in complete working order, with possession.-Preliminary. Wilson, George Ferguson, F.RS. F.C.S. Heather-bank, Weybridge MESSRS. FULLER, HORSEY, SONS, Wilson, James Henry, Oak Hall, East Ham, Essex NAMES of ASSOCIATES. Adair, A., Vale-view, Whitehaven. Bascombe, Frederick, 180, New bond-street, W. Beckett, George Henry, F.C.S., 42, Malvern-road, Dalston, N. .Carpenter, Henry Sanders, F.C.S., The Firs, Alton, Hants Clark, William ing is, B.Sc., Messrs, Luncan, Flockhart, and Co. Ed nburgh, Copley, James, Gregory-street, Nottingham Cowper, Richard, r.C.S., Assoc. R.S.M., 3, The Resider.ces, South Davey G. W. 8 Hawthorne-t rrace, Barking, Essex Firby, Alfred, 2, Fallowfield-terrace, Leeds Gaban, William Patrick, 56, Walton-street, S. W. Gaskell, Francis, Newnham-lodge, Spring grove, Isleworth Gibson, John, Ph.D., F.R.S.E., 29, Greenhill-gardens, Edinburgh Hannay, James Ballantyne, F.C.S., Owens College, Manchest r Hollis, Percy Best, Mersey Chemical Works, Widnes Luff, Arthur Pearson, 13, Lisson-street, Marylebone-road, N.W. Matthews, Charles George, F.C.S., St. John's-lodge, Beckennam Naigamvala, K. D., Elphinstone College Laboratory, Bombay Pearson, Alfred Naylor, 7, Warwick-square, Kensington, W. Thorne, Leonard Temple, Universtats, Wurzburg Laboratorium and CO. are instructed to SELL by AUCTION, at the Palatine Hotel, Manchester, on Thursday, April 17, at 3 o'clock precisely, in one lot, unless an acceptable offer be previously made by private contract, the PRESTOLEE ALKALI WORKS, a freehold property, having a superficial area of 95,741 square yards of land, subject to chief rents amounting to £407 13s. 9d. per annum, with the buildings, plant, machinery, and apparatus erected thereon, capable of manufacturing monthly a product exceeding in the aggregate 2000 tons of soda-ash, bleaching-powder and liquor (by Weidon's patent process), and sulphuric acid, also caustic soda and muriatic acid. The amount expended in the construction of these works has been very large. A valuation was made with great care in 1874 by Messrs. Holmes and Son, the well-known valuers, of Manchester; their estimate then amounted to £99,900, and since that time a sum exceeding £10,000 has been expended. The whole of the works and plant have been well kept, and are conveniently arranged for working. The Bury, Bolton, and Manchester Canal, which forms one boundary of the property, affords facility for economical water carriage, and the Lancashire and Yorkshire Railway is within a very short distance. There is a plentiful supply of water for all manufacturing purposes, free of cost, from the river Croal, and coals are raised from pits in the immediate neighbourhood. Pyrites, salt, lime, and limestone are ail brought by boats direct to the wharf on the canal. The works may be economically worked with a small capital, as arrangements may be made with the vendors for a very considerable portion of the purchase money to remain upon mortgage. Large profits have been realised in the past, and the high reputation of the Prestolee manyfactures in the market will ensure to an energetic man, even at the existing low prices, an ample return for his capital invested and possession of works not surpassed for completeness or compactness by any in the kingdom. May be viewed till the sale. Printed particulars are in course of preparation, and may shortly be had at the Works; at the Palatine and Queens Hotels, Manchester; of Messrs. Wakeman and Bleeck, Solicitors, Warminster; of Messrs Addleshaw and Warburton, Solicitors, Norfolk Street, Manchester; and of Messrs. Fuller, Horsey, Sons, and Co., 11, Billiter Square, London, who are empowered to treat for the disposal by private contract, or an offer for renting would be entertained, WILLIAM AND WILLIAM T. FIELD, MANUFACTURERS of the Celebrated STAFFORDShire blue BRICKS, specially adapted for Chemical Plant, i.e., Acid Towers, &c. Also all other kinds of Best Staffordshire Blue Bricks, Pavings, Plynths, Splays, Copings, &c. &c. Prices and samples on Application. THE CHEMICAL NEWS. VOL. XXXIX. No. 1011. taking place. The glass recovers its phosphorescent power to some extent after rest. In this apparatus a shifting of the line of molecular discharge is noticed. If the coil is stopped and then set going repeatedly, always keeping the oblique pole negative, the spot of green light occurs on the glass at the spot where it should come supposing the discharge were normal to the surface of the pole. But if once the flat pole is made CONTRIBUTIONS TO MOLECULAR PHYSICS IN positive, the next time it is made negative the spot of HIGH VACUA. By WILLIAM Crookes, F.R.S. THIS Paper is a continuation of one " On the Illumination of Lines of Molecular Pressure, and the Trajectory of Molecules," which was read before the Royal Society on the 5th of December last. The author has further examined the action of the molecular rays electrically projected from the negative pole in very highly exhausted tubes, and finds that the green phosphorescence of the glass (by means of which the presence of the molecular rays is manifested) does not take place close to the negative pole. Within the dark space there is absolutely no phosphorescence; at very high exhaustions the luminous boundary of the dark spark disappears, and now the phos. phorescence extends all over the sensitive surface. Assuming that the phosphorescence is due either directly or indirectly to the impact of the molecules on the phorescent surface, it is reasonable to suppose that a certain velocity is required to produce the effect. The author adduces arguments to show that within the dark space, at a moderate exhaustion, the velocity does not accumulate to a sufficient extent to produce phosphorescence, but at higher exhaustions the mean free path is long enough to allow the molecules to get up sufficient speed to excite phosphorescence. At a very high exhaustion there are fewer collisions, and the initial speed of the molecules close to the negative pole not being thereby reduced, phosphorescence takes place close to the pole. light appears nearer the axis of the tube, and instantly shifts to its normal position, where it remains so long as its pole is made negative. There seems no limit to the number of times this experiment can be repeated. A suggestion having been made by Professor Stokes that a third, idle, pole should be introduced between the negative and positive electrodes, experiments are described with an apparatus constructed accordingly. The potential of the idle poles (of which there are two) at low exhaustions is very feebly positive; as the exhaustion gets better the positive potential increases, and at a vacuum so good as to be almost non-conducting, the positive potential of the idle poles is at its greatest. The result is that an idle pole in the direct line of fire between the positive and negative poles, and consequently receiving the full impact of the molecules driven from the negative pole, has a strong positivè potential. It is found that when the shadow of an idle pole is prophos-jected on a phosphorescent screen the trajectory of the molecules suffers deflection when the idle pole is suddenly uninsulated by connecting it with earth. The same result is produced by connecting the idle pole with the negative wire through a very high resistance, such as a piece of wet string, instead of connecting it with earth. A tube, which has already been described in a paper read before the Royal Society on December 5th last, is used to illustrate this deflection. The shadow of an aluminium star is projected on a phosphorescent screen. So long as the metal star is insulated the shadow remains sharp, but on uninsulating the star by connecting it with an earth wire the shadow widens out, forming a tolerably well-defined penumbra outside the original shadow, which can still be seen unchanged in size and intensity. On removing the earth connexion the penumbra disappears, the umbra remaining as before. Experiments are described in which a pole folded into corrugations is used at one end of a tube, the pole at the other end being flat set obliquely to the axis of the tube, and having a plate of mica in front pierced with a hole opposite the centre of the pole. The questions which this apparatus was designed to answer are:-(1.) Will there be two sets of molecular projections from the corrugated pole when made negative, one perpendicular to each facet, or will the projection be perpendicular to the electrode as a whole, i.e., along the axis of the tube? (2.) Will the molecular rays from the oblique flat pole, when this is made negative, issue through the aperture of the screen along the axis of the tube, i.e., direct to the positive pole, or will they leave the pole normal to the surface and strike the glass on its side? With the corrugated pole experiment shows that at high exhaustions molecular rays are projected from each facet to the inner surface of the tube, where they excite phosphorescence, and form portions of ellipses by the intersection of the planes of molecular rays with the cylindrical tube. When the oblique flat pole is made negative, a stream of molecules shoots from it nearly normal to its surface, and those which pass through the hole in the plate of mica strike the side of the tube, forming an oval patch of a green colour. The oval patch in this apparatus happens to fall on a portion of the glass which has previously had its phosphorescence excited by the molecular discharge from the other corrugated pole. The phosphorescence from this pole is always more intense than that from the flat pole, and the glass, after having been excited by the energetic bombardment, ceases to respond readily to the more feeble excitement from the flat pole. The effect, therefore, is, that when the oval spot appears, it has a dark band across it where the phosphorescence from the other pole had been ✦ Abstract of a Paper read before the Royal Society, April 3, 1879. It is also found that the shadow of the star is sharply projected when it is made the positive pole, the negative pole remaining unchanged. These experiments are explained by the results just mentioned, that the idle pole, the shadow of which is cast by the negative pole, has strong positive potential. The stream of molecules must be assumed to have negative potential; when they actually strike the idle pole they are arrested, but those which graze the edge are attracted in. wards by the positive potential and form the umbra. When the idle pole is connected with earth, its potential would become zero were the discharge to cease; but inasmuch as a constant supply of positive electricity is kept up from the passage of the current, we must assume that the potential of the idle pole is still sufficient to more than neutralise the negative charge which the impinging molecules would give it. The effect, therefore, of alternately uninsulating and insulating the idle pole is to vary its positive potential between considerable limits, and consequently its attractive action on the negative molecules which graze its edge. The result is a wide or a narrow shadow, according to circumstances. After a definite shadow is produced, it is found that increasing the exhaustion makes very little change in the umbra, but it causes the penumbra to increase greatly in size. Experiments recorded in the paper already quoted have proved that the velocity of the molecules is greater as the vacuum gets higher, and consequently the trajectory of the molecules under deflecting action, whether of a magnet or of an insulated idle pole, is flatter at high than at low vacua. An experiment is next described, having for its object to 156 Volumetric Estimation of Sulphuric Acid, Tannin, &c. (CHEMICAL NEWS, ascertain whether two parallel molecular rays from two adjacent negative poles attract or repel each other. It is considered that if the stream carries an electric current, attraction should ensue, but if they are simply streams of similarly electrified bodies, the result would be repulsion. Experiment proves that the latter alternative happens, lateral repulsion taking place between two streams moving in the same direction. Many experiments are given to illustrate the law of action of magnets on the molecular stream, but the results are of too complicated a character to bear condensation without the diagrams accompanying the original paper. The molecular stream is sufficiently sensitive to show appreciable deflection by the magnetism of the earth. The author, after numerous experiments, has succeeded in obtaining continuous rotation of the molecular stream under the influence of a magnet, analogous to the wellknown rotation at lower exhaustions. Comparative experiments are given with a "high vacuum" tube, where no luminous gas is visible, but only green phosphorescence on the surface of the glass, and a "low vacuum" tube in which the induction spark passes in the form of a luminous band of light joining the two poles. These two tubes are mounted over similar electro-magnets, the direction of discharge being in a line with the axis of the magnet. Numerous experiments, the details of which are given in the paper, show that the law is not the same at high as at low exhaustions. At high exhaustions the magnet causes the molecular rays to rotate in the same direction, whether they are coming towards the magnet or going from it; the direction of rotation being entirely governed by the magnetic pole presented to the stream. The north pole rotates the molecular discharge in a direct sense, independent of the direction in which the induction current passes. The direction of rotation impressed on the molecules by a magnetic pole is opposite to the direction of the electric current circulating round the magnet. These results offer an additional proof that the stream of molecules driven from the negative pole in high vacua do not carry an electric current in the ordinary sense of the term. The author, after giving details of experiments in which platinum and glass are fused in the focus of converging molecular rays projected from a concave pole, describes observations with the spectroscope, which show that glass obstinately retains at even a red heat a compound of hydrogen-probably water-which is only driven completely off by actual fusion. The permanent deadening of the phosphorescence of glass is shown by projecting the shadow of a metal cross on the end of a bulb for a considerable time. On suddenly removing the cross, its image remains visible, bright upon a dark ground. One of the most striking of the phenomena attending this research is the remarkable power which the molecular rays in a high vacuum have of causing phosphorescence in bodies on which they fall. Substances known to be phosphorescent under ordinary circumstances shine with great splendour when subjected to the negative discharge in a high vacuum. Thus Becquerel's luminous sulphide of calcium has been found invaluable in this research for the preparation of phosphorescent screens whereon to trace the paths and trajectories of the molecules. It shines with a bright blue-violet light, and when on a surface of several square inches is sufficient to faintly light a room. The only body which the author has yet met with which surpasses the luminous sulphides, both in brilliancy and variety of colour, is the diamond. Most diamonds from South Africa phosphoresce with a blue light. Diamonds from other localities shine with different colours, such as bright blue, apricot, pale blue, red, yellowish green, orange, and pale green. One very beautiful diamond in the author's collection gives almost as much light as a candle when phosphorescing in a good vacuum. Next to the diamond, alumina and its compounds are * Like the hands of a watch, April 10, 1879. the most strikingly phosphorescent. The ruby glows with a rich full red, and it is of little consequence what degree of colour the stone possesses naturally, the colour of the phosphorescence is nearly the same in all cases; chemically prepared and strongly ignited alumina phosphoresces with as rich a red glow as the ruby. The phosphorescent glow does not therefore depend on the colouring-matter. E. Becquerel* has shown by experiments with his phosphoroscope that alumina and many of its compounds phosphoresce of a red colour after insolation. Nothing can be more beautiful than the effect presented by a mass of rough rubies when glowing in a vacuum; they shine as if they were red-hot, and the illumination effect is almost equal to that of the diamond under simi lar circumstances. Masses of artificial ruby in crystals, prepared by M. C. H. Feil, behave in the vacuum like the natural ruby. In the spectroscope the alumina glow shows one intense and sharp red line less refrangible than the line B, and a faint continuous spectrum ending at about B. The wavelength of the red line is 6895. The paper concludes with some notes by Prof. Maskelyne, on the connexion between molecular phosphorescence and crystalline structure. The crystals experimented on have been the diamond, emerald, beryl, sapphire, ruby, quartz, phenakite, tinstone, hyacinth (zircon), tourmaline, andalusite, enstatite, minerals of the augite class, apatite, topaz, chrysoberyl, peridot, garnet, and boracite. Of these, the only crystals which give out light are the diamond, ruby, emerald, sapphire, tinstone, and hyacinth. The light from emerald is crimson, and is polarised, apparently completely, in a plane perpendicular to the axis. Sapphire gives out a bluish grey and a red light polarised in a plane perpendicular to the axis. The ruby light exhibits no marked distinction in the plane of its polarisation. Among positive crystals tinstone glows with a fine yellow light, polarised in a plane parallel to the axis of the crystal. So far the experiments accord with the quicker vibrations being those called into play, and therefore in a negative crystal the extraordinary, and in a positive crystal the ordinary, is the ray evoked. Hyacinth, however, introduces a new phenomenon, being dichroic; the colours, in three different crystals, being pale pink and lavenderblue, pale blue and deep violet, and yellow and deep violetblue, polarised in opposite planes. The only conclusion arrived at is that the rays, whose direction of vibration corresponds to the direction of maximum optical elasticity in the crystal, are always originated where any light is given out. As yet, however, the induction on which so remarkable a principle is suggested cannot be considered sufficiently extended to justify that principle being accepted as other than probable. VOLUMETRIC ESTIMATON OF SULPHURIC By ARTHUR G. HADDOCK, A.I.C. IN the volumetric estimation of sulphuric acid by a standard solution of baric chloride I have found that by the usual method of spotting on a black glass plate, it is often extremely difficult to tell exactly when the operation is finished. It is still more so in the estimation of tannin by standard gelatine solution, especially when the extract is highly coloured. I find that by using a small glass mirror instead of the black plate this difficulty is entirely obviated, and that the point of complete precipitation is well and sharply defined-one drop of the standard solution in excess pro. ducing a very distinct reaction. It matters not how highly * Annales de Chimie et de Physique, 3rd series, vol. Ivii., p. 50. |