I40 



NA TURE 



June 9, 1692 



If one of these colonies be transferred to a sterile solution of 

 calcium citrate, it invariably fails to set up a fermentation of the 

 latter, the bacillus having thus by mere passage through the 

 gelatin- medium lost its power to produce this effect. If, how- 

 ever, we take another similar colony and put it into a solution of 

 broth containing calcium citrate, fermentation takes place ; on 

 now inoculating from this to a weaker solution of broth contain- 

 ing calcium citrate, this also is put into fermentation, and by 

 proceeding in this manner we may ultimately set up fermentation 

 in a calcium citrate solution which absolutely refused to be 

 fermented when the bacilli were taken directly from the gelatin- 

 plate. 



Phenomena of this kind clearly indicate that there may be 

 around us numerous forms of micro-organisms of the potentiality 

 of which we are still quite ignorant. Thus, if we were only 

 acquainted with the bacilli I have just referred to from gelatin 

 cultures, we should be quite unaware of their power to excite 

 this fermentation of calcium citrate, which we have only been 

 enabled to bring about by pursuing the complicated system of 

 cultivation I have indicated. It is surely exceedingly probable, 

 therefore, that many of the micro-organisms with which we are 

 already acquainted may be possessed of numerous important 

 properties which are lying dormant until brought into activity by 

 suitable cultivation. 



This power of modifying the characters of bacteria by culti- 

 vation is, I venture to think, of the highest importance in 

 connection with the problems of evolution, for in these lowly 

 forms of life, in which, under favourable circumstances, genera- 

 tion succeeds generation in a period of as little as 20 minutes, 

 it should be possible through the agency of selection to effect 

 metamorphoses, both of morphology and physiology, which 

 would take ages in the case of more highly organized beings to 

 bring about. 



We hear much about the possibility of altering the human 

 race through training from the enthusiastic apostles of education, 

 but even the most sanguine cannot. promise that any striking 

 changes will be effected within several generations, so that such 

 predictions cannot be tested until long after these reformers have 

 passed away. In the case of micro-organisms, however, we 

 can study the effect of educational systems consequentially pur- 

 sued through thousands of generations within even that short 

 span of life which is allotted to us here. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — Dr. Peile, Master of Christ's College, has been 

 re-elected Vice-Chancellor for the ensuing academical year. 



The examination for the Diploma in Public Health will begin 

 on October 4. Candidates are to send their names to the Regis- 

 trary by September 27. 



Prof. Roy announces a special course in Bacteriology, 

 to be given during the long vacation by Mr. Adami, 

 Mr. Kanthack (one of the Leprosy Commissioners), and Dr. 

 Lloyd Jones, beginning on July 8. It is especially intended for 

 candidates, not necessarily members of the University, for the 

 Diploma in Public Health. 



An elaborate scheme for the proposed Mechanical Sciences 

 Tripos has been prepared by a special Syndicate, and appears in 

 the University Reporter for May 31. The Tripos follows the 

 main lines of the Natural Sciences Tripos, and seems to be free 

 from the objections which have proved fatal to former schemes. 



It is understood that the persons on whom hor.orary degrees 

 are to be conferred on June ii, in connection with the 

 Chancellor's inauguration, have been for the most part nominated 

 by his Grace. This will perhaps account for the political 

 character of the list, which is, however, partially relieved by the 

 presence on it of General R. Strachey, and Mr. G. W. Hill, 

 late of the office of the Amci'ican iEphemeris, and known 

 among astronomers for his fine work on the lunar theory. Five 

 of the honorary graduates are Fellows of the Koyal Society. 



The University College of Wales, Aberystwyth, has been 

 admitted to the privileges of a College affiliated to the University. 

 The Mason College of Science, Birmingham, has been associated 

 with the Local Lectures Syndicate in the work of University 

 Extension. 



Dr. W. Howship Dickinson, Dr. Bradbury, and Dr. J. F. 

 Payne have been appointed Examiners in Medicine, Dr. W. S. 



NO. 1 I 80, VOL. 46] 



Playfair and Dr. Griffith Examiners in Midwifery, and Messrs. 

 Herbert Page, Frederick Treves, and Howard Marsh Examiners 

 in Surgery. 



Notice of opposition to the appointment of Sir R. S. Ball to 

 the Directorship of the Observatory has been given. The 

 grounds stated are that the duties of the Professorship of 

 Geometry and Astronomy should occupy the whole time of the 

 Professor, while the energies of the Director, in view of the 

 recent developments of astronomical science, should be entirely 

 devoted to the work of the Observatory. It is also held to be 

 unwise in these circumstances to refuse the munificent offer of 

 Mrs. Adams to provide £10,000 for the endowment of a separate 

 Director. 



SOCIETIES AND ACADEMIES. 



London. 



Royal Society, May 19. — "On the Changes produced 

 by Magnetization in the Length of Iron and other Wires carry- 

 ing Currents." By Shelford Bidwell, M.A., LL.B., F.R.S. 



The changes of length attending the magnetization of rods or 

 wires of iron and other magnetic metals which were first noticed 

 by Joule in 1841, and have in recent years formed the subject of 

 many experiments by the author, have been found t o be related 

 to several other phenomena of magnetism. Maxwell has 

 suggested that they sufficiently account for the twist which is 

 produced in an iron wire when magnetized circularly and longi- 

 tudinally at the same time. The resultant lines of magnetiza- 

 tion, as he points out, take a spiral form ; the iron expands in 

 the direction of the lines of magnetization, and thus the wire 

 becomes twisted. Prof. G. Wiedemann, however, to whom the 

 discovery of the magnetic twist is due, appears not to be satisfied 

 with this explanation, believing the effect to be caused by un- 

 equal molecular friction. 



The subject of magnetic twists has been very fully and care- 

 fully investigated by Prof. C. G. Knott, and in a paper pub- 

 lished last year in the Transactions of the Royal Society of 

 Edinburgh (vol. xxxvi.. Part II., p. 485) he indicates many 

 details in which the phenomena of twist closely correspond with 

 those of elongation and retraction. Assuming their essential 

 identity, and noting that "an increased current along 

 the wire affects the points of vanishing twist in a manner 

 opposite to that in which an increased tension aftects it," 

 Prof. Knott is "inclined to conclude that the pure strain 

 effects of these influences are of an opposite character." 

 Now, since the magnetic elongation of an iron wire is 

 known to be diminished by tension, the remark above quoted 

 amounts to a prediction that in an iron wire carrying a current 

 the magnetic elongation would be increased. "\Ve know 

 nothing so far," Prof. Knott observes, "regarding the changes 

 of length when an iron wire carrying a current is subjected to 

 longitudinal magnetizing forces " ; and it was with the object of 

 acquiring some information on this point, and testing Prof. 

 Knott's prediction, that the experiments described in the present 

 paper were undertaken. The results show that it was amply 

 verified, and thus Maxwell's explanation of the twist receives 

 still further corroboration. 



The apparatus used and the methods of observation were the 

 same as those described in former papers. Each specimen of 

 wire examined was 10 cm. long, and the indications of the 

 instrument were read to one ten-millionth part of the length. 



The wire first used was of soft commercial annealed iron, 075 

 mm. in diameter. The changes of length which it exhibited 

 under the influence of magnetizing forces gradually increased 

 from 13 to 315 C.G.S. units are indicated in the second column 

 of Table I., in which the unit is one-millionth of a centimetre or 

 one ten-millionth of the effective length of the wire. 



The experiment described in the last paragraph was repeated 

 while a current of i ampere was passing through the wire, 

 the several magnetizing forces employed being made as nearly 

 as possible the same as before by inserting the same resistances 

 successively in the circuit. The results appear in the third 

 column of Table I., and show that the maximum elongation had 

 risen from 11 "5 to I4'5 ten-millionths, while the decrement in a 

 field of 315 had fallen from 22-5 to about 17-5. _ 



The current through the iron wire was then increased, by an 

 alteration of the rheostat, to 2 amperes, and, as appears in the 

 last column of the table, there was again a marked increase of 

 the maximum elongation, and decrease of the retraction in a 

 field of 315. 



