June, 1913. 



KNOWLEDGE. 



217 



banks near roads and villages — for the tsetse-fly 

 needs the undergrowth as a breeding place — and in 

 the control of natives living in infected areas by 

 preventing their migration to other parts until they 

 have been proved free of the disease. 



Since trypanosomes do their work of destruction 

 by some poison — toxin — they secrete, or by using up 

 some essential substance in the blood of their host, 

 which the host needs for the continuance of its life ; 

 and since the multiplication of the parasite in the 

 host's blood is unchecked except by the ultimate death 

 of the host, it is safe to conclude that, unlike some 

 bacterial diseases, the body in this case is unable to 

 produce an antitoxin by which to rid itself of the 

 infection. Therefore, I do not think that any 

 " vaccine-treatment " will ever be found of any avail, 

 but the cure must come through the discovery of 

 some drug that shall deal death to the trypanosome 



and yet not poison the patient. It is not, however, 

 that the trypanosome in itself possesses any 

 extraordinary vitality that makes it difficult to kill 

 but it is merely its position in the host's blood 

 which gives it its present unassailable position ; for 

 drugs that are harmful to it are equally harmful to 

 the tissue-cells of the host, and effectually to poison 

 the one means, just as effectually, to poison the 

 other. Trypanosomes in fluid media — blood, and so 

 on — when raised outside the body, only a few- 

 degrees above the normal animal temperature, quickly 

 succumb. Were it possible to keep the infected 

 animal at such a body-temperature without killing 

 it, that, perhaps, would be the simplest method of 

 cure ! Needless to say this is quite an impossibility, 

 and so, notwithstanding all that has been done 

 up to the present, the difficulty in the cure of 

 trypanosome diseases still awaits solution. 



NOTES. 



ASTRONOMY. 



By A. C. D. Crommelin, B.A., D.Sc, F.R.A.S. 



THE MOUNT WILSON ONE HUNDRED - INCH 

 REFLECTOR. — Some good news about this great instrument 

 has arrived from California. It was previously reported that 

 the glass disc for the mirror had proved a failure, but it has 

 now been found that the fault was only in the method of 

 mounting, which caused flexure ; an improved method gave 

 satisfactory results, and the disc has been accepted and paid 

 for, which indicates confidence that it is sufficiently good. 

 We may hope for some wonderful results in stellar astronomy 

 when this giant instrument is complete. Even the sixty-inch 

 shows stars of the twenty-first magnitude. 



THE SPECTRO-HELIOGRAPH.— The Gold Medal of the 



Royal Astronomical Society was given this year to M. Deslandres 

 for his work on the Sun. The address of the Astronomer 

 Royal gives an interesting summary of his work, calling attention 

 to the spectro-heliograms of the lower, middle and upper layers 

 of the solar atmosphere, which are obtained by shifting the 

 second slit to the outside, intermediate, or central region of 

 the K line. In the upper-layer photographs the prominences 

 can be seen both inside and outside the disc, and it is possible 

 to say whether a limb prominence has its base on the near or 

 remote hemisphere of the Sun and to localise it exactly in the 

 former case. The ordinary limb observations of prominences 

 do not admit of this. Another interesting feature of the high-level 

 spectro-heliograms is the system of long dark filaments, which 

 play the same important part in this layer that spots do in the 

 lowest one. They form a network over the whole disc and 

 sometimes persist for several rotations. They are intimately 

 connected with prominences, one of these being generally 

 present where they cut the limb. M. Deslandres finds that 

 they are centres of rotation about a horizontal axis, the spots 

 rotating about a vertical one. It was also found possible to 

 obtain spectro-heliograms of these in the hydrogen light, using 

 the Ha line, though its narrowness made the difficulty greater 

 than in the K line of calcium. The upper layer of hydrogen 

 shows the same filaments as the calcium ones, while the 

 middle layer shows the vortices round spots, which Hale was 

 the first to detect. Deslandres also devised the " Velocity 

 Recorder," which is a spectro-heliograph with a wide second 

 slit, enabling the whole width of the line to be photographed. 

 As the slit traverses the solar disc, variations in the position 

 and width of the line give indications of the motion of gases 

 in the atmosphere of the Sun. He concludes that on the 

 whole the bright regions are descending and the dark filaments 

 ascending. He thinks that the circulation of a sun-spot is 



as follows : — The gases in the surrounding regions are ascend- 

 ing, then they approach the facula and go down in it, a 

 continuous circulation being maintained. If the downward 

 motion prevails, the lowest layer may be pierced and a spot 

 formed, while if the upward current prevails a prominence is 

 formed. He also finds in the varying rotational velocity of 

 different parts of prominences (the base having the more 

 rapid rotation) evidence of the existence of a magnetic field in 

 the higher layers, just as Hale had found it in the vortices 

 surrounding spots. 



Another interesting solar paper was read at the April 

 meeting of the Society : it was by Mrs. Evershed (Kodaikanal), 

 and was accompanied by a beautiful series of prominence 

 photographs. A certain type of explosive prominence appeared 

 to be intimately connected with spots, and in several of these 

 prominences there was evidence of outward motion, which 

 was, however, slow, this being a different result from that 

 found by Slocum, who noted inward motion. The photographs 

 will be reproduced in the Monthly Notices, and it will then 

 be possible to follow the argument more closely. 



SPIRAL THEORY OF THE MILKY WAY.— The idea 

 that the Milky Way may be a spiral has been many times put 

 forward. I think Mr. Proctor was the first to do so. Dr. 

 Easton, who is well known for his studies on the subject, gives 

 in The Astrophysical Journal for March a small-scale diagram 

 of the whole Milky Way from a combination of photographs 

 and eye drawings, also a spiral form that he suggests might 

 account for the appearance, though he adds that he does 

 not insist on the accuracy of the details. It is of the Catherine- 

 wheel kind, consisting of several curved streams radiating 

 from a large nucleus, which he places in Cygnus. The form 

 was suggested by several spiral nebulae, notably the one in 

 Canes Venatici. At many places the streamers point straight 

 towards us, this being his explanation of brighter portions ; 

 since we see a great depth of galactic matter in such streams. 

 He makes one stream pass through the solar system, which 

 seems improbable, as the evidence of the proper motions is 

 that no part of the Galaxy is very near us. The spiral theory is 

 rendered more probable by the fact that a spiral structure is 

 suspected for the Magellanic clouds. 



SPECTROSCOPIC DETERMINATION OFTHE SUN'S 

 ROTATION. — Many astronomers have investigated the Sun's 

 rotation in this manner in recent years. The obvious advan- 

 tage is that it can be extended to all latitudes, while the 

 visual method by the spots is confined to the tropical regions. 

 Moreover the spots are clearly of the nature of great disturb- 

 ances in the photosphere, and there is some objection in 

 using them to give the motion of the undisturbed regions 



