July 30,, 1891] 



NATURE 



301 



of the whole matter is that, unconsciously, I have actually 

 furnished important evidence in favour of your meteoric hypo- 



thesis. 



Sincerely yours, 



J. M, SCHAEBERLE. 



Some time after the arrival of the letter I received the 

 number of the Publications of the Astronomical Society 

 of the Pacific which contained the article referred to, 

 which I have read with the greatest interest. It has been 

 known for some time that Dr. Schaeberle has been able 

 to reproduce the general appearance presented by the 

 corona by means of mechanical contrivances, and that 

 even the polar rays, which were such a noticealale feature 

 of the eclipse of 1878, as I saw it at Separation, can be, 

 in this way, satisfactorily accounted for. 



The point of newest interest, however, is that referred 

 to in Dr. Schaeberle's letter. 



Assuming eruptions most active in the sun-spot zones, 

 and an initial velocity of 380 miles a second, he obtains 

 the following results : — 



(i) All parts of a given unperturbed stream will be in a 

 heliocentric latitude nearly equal to the latitude of the 

 point of ejection. 



(2) For a constant ejective force the periodic time/ 

 will be the same for all parts of the stream. 



(3) The chance of collision of a returning with an 

 outgoing stream varies inversely as the square of the 

 distance of the point of collision from the sun. 



(4) Near the sun, therefore, collisions must occur 

 which tend to retard or stop the outgoing streams, result- 

 ing in a temporary increase in the heat of the combined 

 colliding masses (causing a consequent increase in the 

 brightness of the corona at such places, and at the same 

 time rendering the coronal detail more confused). This 

 heat will tend to be largely dissipated before such masses 

 fiill back into the sun, which they will then reach with 

 comparatively small velocity and low temperature. 

 Lnretarded returning streams on striking the sun will 

 tend to greatly raise the temperature at the points of 

 impact : perturbed returning streams could, of course, 

 strike all parts of the sun's surface. Unperturbed re- 

 turning streams will always fall within the limits of the 

 sun-spot zones. 



(5) So long as the incoming streams are very numerous, 

 the outgoing ones will, in a great measure, be stopped, so 

 that, after the interval /, there will be comparatively few 

 returning streams : a direct result of this state of things 

 is to allow free passage for the outgoing streams, which, 

 since there are now but few collisions, results in (i) an 

 apparent diminution in the brightness of the corona, (2) 

 more regular and sharply defined detail, and (3) in general 

 a more uniformly illuminated solar surface might be 

 expected, when there are but few or no returning streams. 

 The periodic character of this intermittent motion can be 

 -well illustrated by means of a fine vertical jet of water. 

 The vertical vibratory motion of a light ball, often to be 

 seen in water fountains, is also a good illustration. 



(6) If the ejective force is such as to make / about 

 five years, a complete cycle of changes will take place in 

 the time 2/, and after the same manner as is observed in 

 the sun-spot cycle. It is rather remarkable that the 

 aphelion distance of the streams corresponding to this 

 value of / is nearly the same as Jupiter's distance from the 

 sun ; so that the perturbations produced by this planet 

 may have more to do with the regularity of the period 

 than the assumed constant force of ejection. The initial 

 velocity required to just carry a particle from the sun to 

 Jupiter is but little less than a parabolic velocity. For 

 an initial parabolic velocity, Saturn, alone considered, 

 would, on the same hypothesis, cause a complete cycle of 

 less marked changes in twenty years, Uranus in sixty 

 jears, and Neptune in one hundred and twenty years. 

 The comparatively insignificant planets inside of the 



NO. II 35, VOL. 44] 



orbit of Jupiter would cause minor variations, corre- 

 sponding to cycles, which, even for Mars, would be of less 

 than two years' duration. 



(7) The chance of the earth passing through one of 

 these outgoing streams, which have a mean latitude 

 of 15°, is less than it is for an incoming perturbed 

 stream. 



(8) A phenomenon similar to the observed zodiacal 

 light would result from the projection of many such 

 streams in space, and the observed extent of this light 

 proves that the matter which causes this illumination ex- 

 tends to greater distances from the sun than the earth's 

 distance. 



It is evident from the foregoing that the complete state- 

 ment which is to appear shortly will be looked forward to 

 with interest. 



For myself, I am glad to think that the views I put for- 

 ward in the concluding chapter of my " Chemistry of the 

 Sun " will now be looked at from a new point of view. Time 

 will show what the " falls" which take the first place in my 

 scheme, and the second in Dr. Schaeberle's, really are. 

 Certainly I have seen no cause lately to alter the view I 

 expressed in 1887, that the primary cause of solar disturb- 

 ance is the descent of matter on to the photosphere. 



J. Norman Lockyer. 



NOTES. 

 On Monday the Prince of Wales presented the Albert Medal 

 of the Society of Arts to Mr. W. H. Perkin, "for his discovery 

 of the method of obtaining colouring matter from c )al tar, a 

 discovery which led to the establishment of a new and import- 

 ant industry, and to the utilization of larjje quantities of a 

 previously worthless material " ; and to Sir Frederick Abel, 

 "in recognition of the manner in which he has promoted several 

 important classes of the arts and manufactures by the applica- 

 tion of chemical science, and especially by his researches in the 

 manufacture of iron and steel, and also in acknowledgment of 

 the great services he has rendered to the State in the provision 

 of improved war material and as Chemist of the War Depart- 

 ment." The medal awarded to Mr. Perkin was for the year 

 1890; that to Sir Frederick Abel was for the present year. 



We are glad to hear that in consequence of the deputation 

 which waited upon Sir Michael Hicks-Beach on June 5, the 

 Board of Trade have registered the British Institute of Pre- 

 ventive Medicine as a limited liability company, with the 

 omission of the word "limited." 



It seems as if the introduction of large engineering views 

 may soon produce a' very marked effect upon the future of Egypt. 

 Mr. Willcocks, one of the Inspectors of Irrigation, has com- 

 municated an interesting letter to the Times, from which we. 

 select the following remarks on the engineering importance of 

 Dongola: — "The summer supply of the Nile is lamentably 

 deficient for the existing cotton and sugar-cane crops of Egypt, 

 so that all extensions of these valuable crops are out of the 

 question under existing conditions. The Nile Valley in Nubia is 

 eminently suited for storage of water, but up to the present all 

 projects for storing the muddy flood waters of the Nile below the 

 junctions of the Blue Nile and the Atbara have been condemned, 

 as the construction of solid dams would have resulted in the 

 silting up of the reservoirs themselves. This difficulty has dis- 

 appeared now that it has been discovered that open dams can be 

 constructed which will allow the muddy flood waters to flow 

 through, and store the clear winter supply for use in summer. 

 The construction of these dams has been rendered possible by 

 the great success of Stoney's patent roller-gates, which can be 

 worked under heads of 70 feet of water on a scale sufficient to 

 pass the full flood supply of the Nile. At any time now Egypt 



