April lo, 1884] 



NA TURE 



559 



from a Holtz machine to potentials of about 5000 volts as mea- 

 sured on an absolute electrometer. The velocity of rotation 

 was about 200 revolutions per second. The astatised needle 

 was protected v\ ithin a metal case, and was observed in the usual 

 way by a mirror. No defleclion was observed either when the 

 disk was still or when it rotated. Dr. Lecher intends to repeat 

 Rowland's experiment with the original horizontal disposition of 

 the disk. 



Dr. Lecher has al o made another experiment of great 

 interest. A ray of light was divided, as in many experiments 

 on interference, into two parts, which, after passing through two 

 parallel glass troughs, were caused to reunite, giving the u^ual 

 interference-bands. The troughs contained strong solutions of 

 nitrate of silver. By means of electrodes of silver an electric 

 current of 6 amperes strength was carried in opposite directions 

 along the troughs so that in one trough the curient flowed -coitJi 

 the light, and m the other against it. But in no case was any 

 displacement of the fringes observed. Dr. Lecher concludes 

 that the velocity of light is not influenced by a current flowing 

 through the medium. 



Dr. Lecher has made a third and still more interesting ex- 

 periment, attended, however, like ihe preceding, with a negative 

 result. This was an attempt to ] rove wheiher Faraday's famous 

 e.xperiment of rotating the plane of polaiiation by an electric 

 current could be inverted. He has attempted to generate cur- 

 rents by rotating the plane of polarisation of light. The arrange- 

 ment was as follows : — A ray of plane-polarised light was sent 

 through the intericr of two powerful helices of wire situated at 

 some distance from one another. Through the first of these a 

 powerful alternate current ■\\as sen% which impressed upon the 

 ray a rapid oscillation of its plane of polarisation. The second 

 helix was connected to a sensitive receiving telephone in the 

 hope that sounds might therein be heard, as would be the case if 

 the rapid rotations in the plane of polarisation of the ray were 

 capable of setting up currents in the surrounding wire. Abso- 

 lutely nothing was, however, heard. 



A 



BACTERIA 

 VERY distinguished audience assemLled at the Parkes 

 Museum on Thursday evening, March 27, to witr.ess Mr. 

 Watson Cheyne's demonstration of pathogenic microorganisms. 

 The chair was taken by Sir Joseph Lister, Bart. After stating 

 that the great group commonly called Bacteria might most con- 

 veniently be .-ubdivided into four classes — (i) Micrococci (round 

 bodies), (2) Bacteria (small oval or rod-shaped bodies), (3) 

 Bacilli (large rod-shaped bodies), and (4) SpirochEetae and 

 Spirilla (rods spirally twisted), and dwelling on the great variety 

 as «ell as importance of the various parts plajed by this great 

 group in the economy of nature, Mr. Watson Cheyne demon- 

 strated numerous micro photographs taken by Fh-. Robert Koch, 

 as well as some drawings by means of a limelight apparatus. 

 He observed that great ditferer.ces existed au.ong the various 

 bacteria in their behaviour towards the human body : some could 

 be injected without causing any injury, others could not grow in 

 the living body, but could develop in dead portions of tissue and 

 the secretions of wounds, giving rise to poisonous products. The 

 true pathogenic organisms were able to attack the living body 

 and mull i ply in it; they included the organisms which found 

 entrance through some wound, giving lie to the traumatic in- 

 fective diseases, and others which could obtain eiitrance without 

 observable « our.d. Further, certain organisnis, such as the i?. 

 anthracis, were capable of growing outside the body in dead 

 organic substance, while others, such as the B. tuhirculoiis, were 

 apparently only capable of development in the living organism 

 or under artificial conditions which rej^roduced to some degree 

 those existing in the tissues of warm-blooded animals, thcugh 

 capable of long retaining their vitalityin the dry state. With re- 

 gard to the traumatic infective diseases, he ihought that the most 

 absolute proof had been furnished that the bacteria found in them, 

 andnothii'g el-e, were the causes of these diseases. To establish 

 such a proposition it was necessary that an organism of a definite 

 form and with definite characteristics .-hould always be found in 

 the blocd or in the affected \ art. The blood or the affecttd part 

 when inoculated into another animal of the same species must 

 produce the same disease. When the blood or the affected part 

 was inocukited on a suitable soil outside the body, the micro- 

 orj;anisms grew, and must be indefinitely pro pa gated on similar soil. 

 When in this manner the organisms had been separated from 



the remains of the materials in which they were embedded, their 

 inoculation in an animal must produce again the same disease, 

 the same organisms being found in the diseased parts. These 

 conditions had now been fulfilled with regard to anthrax, septi- 

 cemia of the mouse, erysipelas, tuberculosis, glanders, and 

 acute pneumonia. With regard to typlioid fever, relapsing 

 fever, cholera, and ague, the evidence was very strong, but not 

 conclusive. Mr. Watson Cheyne concluded by dvvelliig on the 

 importance of surrounding circumstances, chiefly those summed 

 up in the phrase unhygienic conditions, as concomitant causes of 

 di; ease by preparing the blood for the attacks of these micro- 

 organisms. 



The chairman, Sir Joseph Lister, dwelt upon the important 

 fact that the organisms which produced particular diseases were 

 only able to develop under very special conditions, instancing 

 the bacillus which caused septics-mia in the house mouse, but 

 which was unable to produce any deleterious effect on the field 

 mouse. He thought this fact, which showed that the very 

 slight difference in the blood of these two animals was sufficient 

 to alter the conditions favourable to the development of the 

 bacteria, might prove of very great interest, as it was possible to 

 conceive that by the administration of some medicines, sufficient 

 alteration might be produced in the blood of the human system 

 to kill off or to prevent the development of any special bacteria 

 on the first appearance of the symptoms of the disease in the 

 patient. Sir Joseph Lister concluded by referring at some length 

 to the impoi tance of Pasteur's researches on modified virus. 



Prof. Humphry paid an eloquent tribute to the great work which 

 Sir Joseph Lister had already achieved, and looked forward with 

 a lai-ge hope to the future of medicine. 



THE STABILITY OF SHIPS 

 pROFESSOR ELGAR has recently made two important 

 contribuiions to this important question ; the first was 

 read before the Royal Sccitty on March J3 last. The main 

 object of the paper was to exhibit the manner in w hich the 

 stability of a ship varies with changes of load and draught 

 of vater such as merchant steamers are liable to. None 

 of the properties possessed by a ship is more vital to her 

 safety and efficiency than that of stability. At the same 

 time none is depeirdent for its existence and amount upon so 

 many or such diverse and variable circumstances as it. The 

 stability of a ship, both as regards moment and range, is affected 

 not only by the position of her centre of gravity, \\ hich largely 

 depends upon stowage, but also by draught of water. If the 

 centre of gravity be kept fixed in position at various draughts of 

 water, the stability will still vary very considerably with the 

 draught, and often in a manner that contains elements of 

 danger. 



The usual practice in investigating a ship's stability is to calcu- 

 late a curve of metacentres, and one or more curves of stal ility 

 at certain fixed draughts of water and with given positions of 

 centre of gravity. The curve of met.acentres gives the height at 

 all draughts of water above which the ceutre of gravity cannot 

 be raised without making the ship unstable when upright, and 

 causing her to lie over more or less to one side. The ordinates 

 of the curve of stability represent the lengths of the righting 

 arms, which, multiplied by the weight of the ship, give the 

 righting moments at all angles of inclination from the upright. 

 Ihe stal ility of numerous vessels, both of the Royal Navy and 

 mercantile marine, have been inve-tigated in this manner for 

 certain draui;hts of water, and a great amount of inforniation 

 obtained respecting the variation of stability with inclination at 

 such draughts, and the angle at which the stability vanishes in 

 many classes of ships. The peculiar dangers attaching to low 

 freeboard, especially when associated with a high centre of 

 gravity, have been fully discussed aid made known. 



Curves of itability have been chiefly constructed for deep and 

 moderate draughts; the character of the stability which is often 

 to be found associated with very light draught, appears to have 

 hitherto e.caped attention. As a matter of fact, light draught is 

 often as unfavourable to stability as low freeboard, and in some 

 cases mere so. The general opinions that have tiil recently pre- 

 vailed upon the subject appear to have been based upon a vague 

 impres i<n that so long as a vessel has a high side out of water, 

 and any metacentric height, she will have great righting moments 

 at large angles of inclination and a large range of stability. It 

 was shown at the Daphne inquiry, held by Sir E. J. Reed in 



