5oo 



NA TURE 



[April j 2, 1906 



product, actinium X, could be separated from actinium. 

 Actinium X produces the emanation, and this in turn the 

 active deposit. The similarity between these two sub- 

 stances is even closer, for I have found that a new pro- 

 duct is present in actinium which is intermediate between 

 actinium and actinium X, and, from analogy to thorium, 

 will be called for convenience "radio-actinium." This 

 product emits a rays, is half-transformed in about twenty 

 days, and is the parent of actinium X. 



The separation of radio-actinium from an actinium solu- 

 tion in radio-active equilibrium can be often accomplished 

 by producing a very small precipitate in the solution, which 

 settles down slowly and carries with it the new product, 

 while most of the actinium and actinium X remain in the 

 solution. Amorphous sulphur was found to be very con- 

 venient for that purpose. To a fairly strong hydrochlorii 

 acid solution of actinium some sodium thiosulphate was 

 added, and the small amount of sulphur was allowed to 

 settle down in the cold. After filtration the precipitate was 

 tested for activity. It showed a strong a-ray activity, but 

 comparatively very little /3-ray activity, and gave out very 

 little emanation. 



The a-ray activity steadily rises to a maximum after 

 about three weeks, the activity then being about two or 

 three times its initial value. The activity then decays and 

 ultimately according to an exponential law, with a period 

 of about twenty days. The 0-ray activity and emanating 

 power reach a maximum at the same time, and decay with 

 the same period. This rise of activity to a maximum is 

 due to the formation of actinium X from the radio- 

 actinium. This is shown by the increase of the emanating 

 power, and was also verified by direct separation of 

 actinium X from the radio-actinium. For instance, if one 

 separates the actinium X when the activity of the radio- 

 actinium is decreasing, the activity of the residue again 

 rises and varies in the same way as in the above desi ribed 

 experiment. Actinium itself, freed from all its products, 

 gives out practically no a or rays, but then slowly in- 

 creases in activity, reaching a maximum after about four 

 months. Godlewski obtained almost inactive actinium, 

 showing that he had unknowingly separated the new pro- 

 duct from the actinium. I have observed that when dis- 

 solving actinium in hydrochloric acid, generally a small 

 portion remains undissolved, and this fraction contains 

 radio-actinium to a large extent. 



Giesel long ago stated that his preparations of emanium 

 increased in activity for about six months. This may prob- 

 ably be explained by the formation of radio-actinium. In 

 a recent paper, Marckwald (Ber. d. d. chem. G., 1905, 

 2264) compared the chemical properties of actinium and 

 emanium, and concluded that actinium and emanium were 

 not identical, but the latter was the parent of the former, 

 the activity of his actinium decaying in the course of several 

 months. This is in contradiction with Debierne's state- 

 ment that his actinium does not lose its activity. The 

 decaying substance, separated by Marckwald, which he con- 

 cluded to be the actinium of Debierne, may possibly be the 

 product radio-actinium, because a precipitation of thorium 

 with sodium thiosulphate carries down the radio-actinium 

 also. But it remains to be explained why his actinium 

 did not rise at first, or why it did not seem to contain 

 actinium X. 



It may be mentioned that the above described experiments 

 were carried out both with the actinium of Debierne and 

 the emanium of Giesel. The same results were obtained 

 in both cases. 



A more complete account of these experiments will be 

 given later. Hahn . 



McGlll University; Montreal, March 27. 



The April Meteors. 

 These meteors will return this year at a favourable 

 period, the moon being near new and only visible as a 

 slender crescent for a short time before sunrise. If the 

 atmosphere should prove clear during the night following 

 Saturday, April 21, a number of Lyrids will probably be 

 seen. The shower is likely to reach its best after "mid- 

 night, when the radiant at 2710 + 3^° will have attained a 

 tly high altitude to favour the visible distribution 

 of its meteors. 



NO. 1902, VOL. JZ\ 



The display is seldom very rich, and has not developed 

 striking brilliancy since 1S03, but it sometimes offers fairly 

 conspicuous features, as in 1901. Usually it does not equal 

 the strength of the annual Perseid shower of August, and 

 it is certainly of much shorter duration, for its period of 

 special activity is often confined to a few hours. In 1901 

 the Lyrids were pretty bright and plentiful on April 21, 

 though on the previous night the display could be scarcely 

 recognised during a long watch. An interesting feature of 

 this system is that its radiant, like ih.it ol 1 In- August 

 meteors, exhibits a daily motion eastwards amongst the 

 stars. This displacement is, however, very difficult to trace 

 owing to the brief duration of the shown, and 10 its com- 

 parative feebleness at many of its returns. 



Observers would do well to watch attentively for early 

 Lyrias on April 18 and 19, and for late members of the 

 stream on April 22, 23, and 24 next. Individual meteors, 

 accurately recorded on these dates, may be regarded as very 

 valuable, since it will be possible to compare their paths 

 with duplicate observations secured elsewhere, and thus 

 their radiant points and heights in the air may be deter- 

 mined with trustworthy precision. 



Meteors from streams contemporary with the Lyrids are 

 usually somewhat rare, but in recent years two showers of 

 slow-moving meteors have been well pronounced from 

 southern positions at iS9°-3i° and 2iS°-3i c '. 



\Y. F. Denning. 



1 he interesting I.yrid meteor shower passed unobserved 

 last year owing to the generally unsatisfactory state of the 

 weather that prevailed at the time of its expected appear- 

 ance. In the event of better atmospheric conditions 

 obtaining at the present epoch, the Lyrids are likelv to be 

 strongly in evidence, as the circumstances that regulate 

 the intensity of these meteor apparitions will be ex- 

 ceptionally favourable. According to calculations by the 

 writer, the Lyrid shower will fall in 1906 on the night 

 of April 19, and will be visible at least in part from both 

 sides of the Atlantic, though the main bulk of the display 

 will descend over the American continent. The earlier 

 maxima on April 19 fall due about ioh. 30m. and 14b. 30m. 

 G.M.T. ; the second and stronger phase of the shower will 

 culminate at :9b. 30m., and will be followed by two other 

 maxima, one of which occurs on April 19 23b. and the 

 other on April 20 2I1. The last and final outburst of 

 meteoric activity will, of course, completelv elude observ- 

 ations over the American continent. Of the minor showers 

 associated with the period, the most prominent will be 

 visible on the nights of April 23 and 25 ; on the former 

 there is a well defined maximum at i(h., while on April 25 

 two or three maxima will take effect between oh. and 

 I2h. 30m. John R. Henry. 



April 7. 



Sea-sickness and Equilibration of the Eves. 



In connection with the above subject, which Mr. Sang 

 brought under the notice of your readers in Your number 

 for March 29, I would like to point out that it has 

 been long known that the eyes may play an important part 

 in sea-sickness. When making some investigations con- 

 nected with a " New Variety of Ocular Spectrum " (Proc. 

 Roy. Soc. Edin., vol. x.), I found that by acting on the eyes 

 alone a very disagreeable sickness, similar to sea-sickness, 

 could be easily produced. The subject was comfortably 

 seated in a chair with his head in a large cylindrical box. 

 The box was open below, but partly closed on the top 

 by a circular piece of wood by which the box was 

 suspended. The cylindrical sides of the box were made 

 of tracing paper having broad black vertical bands painted 

 on it. When the box was rotated on a vertical axis, the 

 black and white vertical bars passed in succession in front 

 of the observer. The effects on the subjects were various ; 

 sometimes they felt as if they were rotating in a direction 

 the opposite of that of the box, but the most certain 

 result was a very disagreeable sickness, which continued 

 for some time after the experiment was made. Personally, 

 I find the best preventive of sea-sickness is to lie down 

 and rend anything I may be interested in, holding the book 

 in such a position that it shuts out the view of all other 

 objects. John Aitken. 



Ardenlea, Falkirk, N.B., March 31. 



