November 9, 1888.] 



SCIENCE. 



219 



cussion of the unusual optical phenomena of the atmosphere, of 

 which so much has been written. This part is divided into a num- 

 ber of sections, of which the first describes fully the phenomena, 

 and is illustrated by two magnificent chromolithographs. In the 

 long discussion on the proximate cause of the unusual twilight 

 phenomena, F. A. Rollo Russell arrives at the conclusion that a 

 dry haze at a great altitude was their cause. The physical con- 

 ditions of this phenomenon were the reflection of sunlight on small 

 vitreous surfaces when the intervening air is darkened. He rejects 

 the theory that condensed vapor caused the unusual twilight phe- 

 nomena, for a number of reasons, principally because spectrum ob- 

 servations and the nature of the corona do not support this view. 

 Besides this, the structure of the haze resembled more that of 

 smoke than that of the highest clouds ; and previous effects seen in 

 years of great eruptions, and in places affected by an excess of dust 

 in the air, are very much like those observed in 1 883 and the follow- 

 ing years. In the same section of the report the colored appear- 

 ances of sun and moon, which were confined to the tropics, the sky 

 haze, and the corona, are discussed. E. Douglas Archibald, who 

 is the author of the last-mentioned part of the report, describes 

 the corona, which is generally known as ' Bishop's ring,' very 

 thoroughly, and shows that it was probably formed in the haze 

 stratum, and that it was formed by diffraction. Its great size 

 proves that this haze was composed of exceedingly small particles, 

 the diameter of which is computed at .00159 of "i millimetre. The 

 occurrence of a corona at a very high altitude, as well as the gen- 

 eral absence of accompanying refractive halos, tends to show that 

 the particles through which the diffraction took place were solids 

 and dust rather than ice. Although the corona was associated 

 with the twilight glows and colored suns in being produced by the 

 same elevated haze, it was physically distinct from either, and 

 probably contributed only very slightly to the glows after the sun 

 sank below the horizon. 



A long list of dates of the first appearance of optical phenomena 

 — a result of a careful scrutiny of numerous periodicals, logs, and 

 of an extensive correspondence — serves as the basis of a study of 

 the geographical distribution of the various sky phenomena, which 

 proves that it spread rapidly westward, having a velocity of about 

 seventy-six miles an hour. 



The researches of E. Douglas Archibald on the height of the 

 glow stratum are of great interest. We will not enter here upon 

 his discussion of Professor Kiessling's theories, as this was tlie sub- 

 ject of a letter recently published in Science (No. 298). The prin- 

 cipal results of his inquiry are the following: In the brilliant 

 glows which began in the tropics after the eruption of Krakatoa on 

 Aug. 26 and 27, there is distinct evidence of a primary glow caused 

 by the direct rays of the sun, and of a secondary glow succeeding 

 this, and due to reflection of the primary glow through the same 

 stratum. These primary and secondary glows correspond to the 

 first and second crepuscular spaces of ordinary twilight, the main 

 difference between the secondary of the present series and the or- 

 dinary second crepuscular space being that the former was colored, 

 whereas the ordinary second twilight is white, and seen only from 

 high altitudes or in peculiarly favorable circumstances. The glow- 

 causing material appeared suddenly and at about its greatest height 

 at first near Krakatoa, and on its subsequent spread into the extra- 

 tropics it appeared at a lessened altitude. The height of the upper 

 or middle part of the stratum progressively diminished from 121,000 

 feet in August, to about 64,000 feet in January, 1SS4. By April, 

 1 884, a considerable portion of the larger reflecting particles had 

 sifted out by gravitation, causing a minimum duration and brilliancy 

 of the secondary glow. As this occurred simultaneously with a 

 maximum development of the corona, it appears probable that a 

 large portion of the finer material remained in suspension at nearly 

 the same height as at first, and that, having become more homo- 

 geneous than at first, it was rendered capable of exerting its max- 

 imum diffractive power. In the autumn and winter months of 

 1SS4 and 1 885 the brilliancy of the glows was partially renewed, and 

 thus it is rendered impossible to arrive at any certain deductions 

 regarding the rate of descent of the stratum as a whole. The final 

 effects of the glow-causing material were produced by the pro- 

 longed reflection from the lofty stratum of rays partly deprived of 

 their red component by the action of the stratum itself, and to a 



much larger extent subsequently deprived of their blue components 

 by the ordinary dust and vapor particles of the lower atmosphere. 

 It was therefore mainly an intensification of ordinary twilight phe- 

 nomena, consequent on the presence, at a lofty altitude, of solid 

 particles not usually existent there. 



The whole volume is full of information of the greatest value, 

 and the mass of material collected, as well as its thorough discus- 

 sion and the clear mode of its treatment, deserves our fullest ad- 

 miration. 



THE UNITED STATES FISH COMMISSION'S WORK 

 DURING THE PAST SEASON. 



The United States Fish Commission has accomplished more, 

 both of practical work and in the line of original investigation look- 

 ing to practical work in the immediate future, this year than dur- 

 ing any previous season of its history. A brief review of its work 

 in both of these departments is given herewith. 



An account of the shad-hatching operations of the commission 

 last spring, and a description of the experiment of shipping lobsters 

 to California, and the planting of them in the Pacific Ocean north 

 and south of San Francisco, were given in Science (xi. 246, xii. 27) 

 several months ago. In connection with shad-hatching. Com- 

 missioner McDonald has been trying this summer a very important 

 and interesting experiment. It is well known that the young shad- 

 fry hatched at the United States Fish Commission stations are not 

 kept until they become little breathing fishes. No means of ac- 

 commodating them have heretofore existed. It is also known that 

 the mortality among young shad is far greater in the earlier than 

 in the later periods of their existence. The longer they live, the 

 better the chance they have of continuing to live. It is known that 

 only an infinitesimally small percentage of the shad-fry placed in 

 rivers in the spring survive and come to maturity ; but so enormous 

 is the number hatched and planted, that those that do escape the 

 scores of enemies they encounter are sufficient to stock abundantly, 

 in a few years, the stream in which they are placed. 



This year Colonel McDonald secured on a government reserva- 

 tion in Washington the use of a pond about six acres in extent. In 

 this he caused to be placed, in June, two million shad-fry, and there 

 are now in the pond eight hundred thousand young breathing shad 

 from three to four inches in length. These will all be turned into 

 the Potomac next spring, when they will be much larger than now ; 

 and the result will be that the number of fishes put into the river 

 at the opening of the next season will be three times as great as the 

 number taken out last season. The percentages of survivals is 

 probably some thousands of times greater than if the fry had been 

 placed in the river soon after they were hatched. In connection 

 with the work of stocking other streams, and in view of the success 

 that has attended this first experiment, much attention will here- 

 after be given to the propagation of shad in ponds. 



During the past summer a new and very important branch of 

 work has been taken up. When a freshet occurs in the Lower 

 Mississippi River, it inundates a belt of country of an average 

 width of about sixty miles, and the territory along its tributaries is 

 covered with water to an extent varying with the topography of the 

 country and the sizes of the rivers. These floods carry with them, 

 of course, enormous quantities of the indigenous fishes of the rivers ; 

 and when the waters recede, ponds and lakes are left in the fre- 

 quent depressions of the surface. These often actually swarm 

 with fishes and with the millions of fry that have been naturally 

 hatched in them. But later in the season a majority of these ponds 

 and lakes dry up. and not only the mature fishes, but the millions 

 of young ones perish. Colonel McDonald this year sent to these 

 Western and Southern rivers the cars of the Fish Commission, 

 with a suflicient force to seine these ponds and lakes, gather up the 

 small fishes, and to plant them in the rivers where they naturally 

 belong, many of which have been depleted by over-fishing and by 

 the effects of the floods. More than a hundred thousand young 

 fishes were thus planted during the past season ; and it is the in- 

 tention of Commissioner McDonald, in restocking the rivers of the 

 West and South with indigenous fishes, to utilize in the way de- 

 scribed nature's great hatcheries, instead of incurring the much 

 greater risk and expense of artificial propagation. 



The rivers operated upon during the past season were the Ohio 



