June iS, 1908] 



NATURE 



151 



and subculturing-, so that a gradual acclimatisation 

 to an aerobic condition is brought about; other 

 methods are also described. The author then_ re- 

 lates his experiences with such anaerobic organisms 

 as the Bacillus perfringens, the bacillus of malignant 

 oedema, and the bacillus of tetanus, and concludes 

 with a critical examination of his results in order 

 to detect fallacies. 



Dr. Kiister's little book will be very useful in the 

 laboratory, as it gives a fairly complete summary, 

 with bibliography, of the methods of isolation and 

 cultivation of micro-organisms, including protozoa, 

 mvxomvcetes, algje, fungi, and bacteria, together with 

 the formulcE and mode of preparation of the nutrient 

 media. A book covering so wide a field will naturally 

 be unequal, and the best sections are probably those 

 dealing with the algee, fungi, and special groups oi 

 bacteria. R. T. Hewlett. 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part 0/ Nature. 

 No notice is taken of anonymous communications.] 



Distant Electric Vision. 



Referring to Mr. Shclford Bidwoll's illuminating com- 

 munication on this subject published in X.vture of June 4, 

 may I point out that though, as stated by Mr. Bidwell, it 

 is wildly impracticable to effect even 160,000 synchronised 

 operations per second by ordinary mechanical means, this 

 part of the problem of obtaining distant electric vision can 

 probably be solved by the employment of two beams of 

 kathode rays (one at the transmitting and one at the 

 receiving station) synchronously deflected by the varying 

 fields of two electromagnets placed at right angles to one 

 another and energised by two alternating electric currents 

 of widely different frequencies, so that the moving 

 extremities of the two beams are caused to sweep synchron- 

 ously over the whole of the required surfaces within the 

 one-tenth of a second necessary to take advantage of visual 

 persistence. 



Indeed, so far as the receiving apparatus is concerned, 

 the moving kathode beam has only to be arranged to 

 impinge on a sufficiently sensitive fluore'cent screen, and 

 given suitable variations in its intensity, to obtain the 

 desired result. 



The real difficulties lie in devising an efficient trans- 

 mitter which, under the influence of light and shade, shall 

 sufficiently vary the transmitted electric current so as to 

 produce the necessary alterations in the intensity of the 

 kathode beam of the receiver, and further in making this 

 transmitter sufficiently rapid in its action to respond to 

 the 160,000 variations per second that are necessary as a 

 minimum. 



Possibly no photoelectric phenomenon at present known 

 will provide what is required in this respect, but should 

 something suitable be discovered, distant electric vision 

 will, I think, come within the region of possibility. 



A. A. Campbell Swintox. 



66 Victoria Street, London, S.W., June 12. 



Prominences and Coronal Structure. 



Pressure of work in other directions prevented me from 

 writing these lines before to-day. They have reference to 

 an article contained in Nature for April 2, in which Dr. 

 Lockyer describes what he considers a triple concentric 

 arc formation in the upper chromosphere similar to coronal 

 structures observed during the eclipses of 1S98, 1901, and 

 1905. Through the kindness of Prof. Hale, the British 

 Astronomical Association is in possession of a photographic 

 slide showing a composite calcium spectroheliogram taken 

 of the sun's disc and chromosphere on July 17, 1907, i.e. 

 the same date as the South Kensington one. Prof. Hale 

 took the picture at 6.46 a.m. P.S.T., while Dr. Lockyer 



NO. 2016, VOL. 78] 



took his at South Kensington at 3.14 p.m. G.M.T. There 

 is thus a difference of something like half an hour between 

 the two exposures, that at Mount Wilson being the earlier 

 one. Comparing the two spectroheliograms, it becomes 

 evident that what Dr. Lockyer considers concentric coronal 

 arcs, due to eruptive action either immediately in front or 

 in the rear of the formation, constitute in reality the debris 

 of an eruptive prominence. I happened to be observing 

 the sun at the time, starting about 1.30 p.m. L.T., 

 having also had the sun under observation early in the 

 morning, and an extract of my notes reads thus : — 



" July 17, 1907, 7 a.m. — In S.L.E. there is something 

 hatching, the limb looking very uneven and the chromo- 

 spheric lines contorted, with strong Dj absorption effects 

 being on view there from time to time. 



" Ditto, 1.30 to 2.20 p.m. — Fine eruptive prominence in 

 L.S.E., where something was preparing this morning. 

 Great displacement of Ha to red side, and the prominence 

 seems to rush en bloc away from the observer and in an 

 almost horizontal direction towards the south, rising 

 radially but little, and dissolving from a stout, dense, and 

 bright stem into a number of bright, more or less parallel 

 layers or striae." 



Great activity continued in the S.E. qu.ndrant for the 

 next three days. The Mount Wilson picture shows what 

 I observed in the spectroscope, viz. a strong dense stem 

 breaking forth in lower L.S.E., curving immediately over 

 to the south (as can be gathered from the great dis- 

 placement observed, the real direction must have been 

 south-east), the stem dissolving into a complicated struc- 

 ture of branches a good distance away to the south of the 

 point of origin. 



1 had to leave the instrument at 2.20 p.m., when a few 

 minutes later Prof. Hale in far-away California exposed 

 his plate, to be followed soon after by Dr. Lockyer in 

 South Kensington. It is quite feasible to think that when 

 the exposure was made at South Kensington, the frag- 

 ments, already in parallel arrangement when I left the 

 instrument, partook also of some kind of concentric 

 curvature, which is, indeed, indicated on Prof. Hale's 

 spectroheliogram. As Dr. Lockyer mentions the absence 

 of an underlying prominence to the concentric arcs 

 he discerns in his picture, I deemed it in order to 

 mention the above facts. I have not the slightest inten- 

 tion by so doing to doubt the great likelihood that con- 

 centric coronal arcs, such as those observed, for instance, 

 by Mr. Wesley, are due to eruptive action from under- 

 neath, but in the case at present under consideration this 

 seems not to have been the case in this more limited sense. 

 I feel sure that Dr. Lockyer will come to the same con- 

 clusion when he compares the two spectroheliograms in 

 the light of my observational notes given above. 



.Albert .'\lfred Buss. 



2 Lansdowne Terrace, Grosvenor Square, Ashton- 



on-Mersey, near jlanchester, May 28. 



The Action of Radium Salts on Glass. 



The letter of Mr. Phillip in Nature of April 9 led me 

 to examine some tubes containing radium salt which have 

 been in my possession for some years. Some had become 

 very purple owing to the action of the radium, whilst 

 others were not coloured at all. The amount of coloration 

 did not seem to depend upon the activity of the prepara- 

 tion ; in fact, the deepest coloration — with one exception — 

 was that due to a salt supposed to contain only one- 

 thousandth of its weight of radium salt. 



Certain kinds of glass when exposed to the bright sun- 

 shine of South Africa take a coloration similar to that 

 produced by radium salt ; I therefore thought that it 

 might be interesting to observe the effect of sunlight upon 

 a specimen of glass coloured by radium. With this object 

 I exposed one of the coloured tubes to the action of the 

 sunlight, and after twelve days' e.xposure the colour has 

 been almost removed. 



I have one tube which contained radium salt of about 

 one million units activity ; where the salt had rested 

 against the tube almost black spots have developed. I 

 shall e.xpose this tube to the continued action of sunlight. 



VV. A. Douglas Rudge. 



University College, Bloerafontein, O.R.C., May 14. 



