SCIENCE. 



3°9 



ate actions in the mandibles, just as contact of the lips 

 with an external body sets up sucking in the infant. All 

 these movements depend upon what we call instiuct — 

 that is to say, organic habits registered in the nervous 

 system of the race. They have arisen by natural selec- 

 tion alone, because those insects which duly performed 

 them survived, and those which did not duly perform 

 them died out. After a considerable span of life spent in 

 feeding and walking about in search of more food, the 

 caterpillar one day found itself compelled by an inner 

 monitor to alter its habits. Why, it knew not ; but, just 

 as a tired child sinks into a sleep, the gorged and full-fed 

 caterpillar sank peacefully into a dormant state." 



Of course all this may have been written in joke. The 

 writer may possibly be laughing at evolutionists. The 

 " inward monitor " of the " gorged and full-fed caterpil- 

 lar " undoubtedly looks rather suspicious, but one hardly 

 likes to hint at anything so serious. Evolutionists will, I 

 dare say, repudiate such " evolution " as a mere travesty, 

 but it is quite time that half-a-dozen evolutionists who 

 agree on main points should clearly state their belief. 



In conclusion, let me ask you as students of nature's 

 processes, whether you have not seen enough to convince 

 you that the revival of the assumption which has been I 

 abandoned and reintroduced many times during the last 

 few centuries, that the lifeless is the sole origin of the 

 living — that in fact the non-living and the living are one 

 —is now unjustifiable, and cannot be reasonably enter- 

 tained. This monstrous fallacy, though taught with the 

 greatest confidence, is based on assumption, and is sup- 

 ported by arbitrarily selected facts, and by not a few mis- 

 representations and dogmatic assertions. Whenever any 

 form of this false doctrine has been successfully forced j 

 into popularity, it has led to the adoption and propaga- 

 tion ot the most grievous errors and grotesque conceits. 



COMET OBSERVATIONS AT PRINCETON. 



The weather has been so unfavorable at Princeton, 

 that we have been unable to make any very satisfactory 

 measures upon the spectrum of the comet. On Saturday 

 evening the comet was visible fairly for an hour or so, 

 before it descended into a bank of cloud. On Sunday 

 evening it was beautifully seen for about half an hour, 

 and then was obscured by a fog which still continues. 



The spectrum of the nucleus is very bright. It is ap- 

 parently continuous, though there may be a little special 

 emphasis at the points where the usual carbon lines 

 ought to appear. The spectrum of the coma and of the 

 tail is precisely like that of most comets, showing three 

 bands which coincide sensibly with those given by the 

 flame of a Bunsen gas-burner, presumably due to a hy- 

 drocarbon of some sort. 



On Saturday evening the nucleus looked much like a 

 star-fish, having five projecting points formed by jets of 

 light protruding from the central globe to a distance of 

 from four to ten seconds of arc. These jets were not 

 equal in length or brightness, and were not symmetrically 

 disposed with reference to the axis of the comet's tail. 

 Two of them were somewhat curved, they were all dif- 

 fuse and blunt at the extremity, rather than pointed. 



On Saturday, instead of jets, the nucleus had a nearly 

 circular envelope surrounding it, sharply defined from 

 the coma. Its diameter was perhaps 20", but the fog 

 came on before any measures could be made. This disc 

 of light, surrounding the nucleus, was not uniformly 

 bright: — it was more brilliant on the side next the Sun. 

 and there was a curious dark opening in it of oval form. 



some 20 one side of the axes of the tail. We were pre- 

 paring to study the spectrum of this en\ elope critically, 

 when we were cut off by the mist. 



Although the Comet is now receding from both Sun 

 and Earth.it is rising so much higher in the Northern 

 Sky each night, that if the weather becomes favorable, it 

 may yet be possible to get something more satisfactory ; 

 but just at present the rain is pouring and the prospect 

 is rather dreary. C. A. YOUNG. 



Princeton, N. J., June 27, 1881. » 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. No notice is taken of anonymous communi- 

 cations^ 



LOCUSTS AND SUN SPOTS. 

 To the Editor of "SCIENCE :" 



Sir: Perhaps you will permit me to explain one in- 

 apposite word occurring in my communication on the 

 above subject. 



When I stated that European migrants come north and 

 east, I should rather have said north and west, the set of 

 the migrations, as far as known, is on European areas 

 north and west ; and in this direction, butterflies, sphinx 

 moths and locusts, whose point of departure has been 

 traced to Southern Asia or Northern Africa, travel period- 

 ically ; the occurrence being made known to us by their 

 vanguard, so to speak, sweeping over the eastern shore 

 of Great Britain. That this track is not voluntarily chosen 

 by instinct, but rather due to a prevailing south-easterly 

 direction of the winds, rests now-a-days on a great 

 amount of experience. A. H. SwiNTON. 



Guildford, Eng., June, 1881. 



THE BLUE COLOR OF THE SKY. 



Prof. Cornu having established the fact that the at- 

 mosphere of the earth exercises an energetic absorption 

 upon the ultra-violet rays of the spectrum, whose limit 

 varies according to the statement of the atmosphere and 

 the altitude of the sun. Prof. Hartley sought to attribute 

 this limitation to the influence of ozone. His experiments 

 have demonstrated. 



1. — That the ozone is a normal constituent of the 

 higher atmosphere, where it is more abundant than on 

 the earth. 



2. — That this quantity of atmospheric ozone suffices to 

 limit the spectrum in the ultra-violet region, without con- 

 sidering the absorption caused by the great density of the 

 oxygen and nitrogen. 



3. — That the blue tint of the atmosphere is due to the 

 presence of ozone. 



In respect of this last point, Prof. Hartley remarks 

 that, if the ozone exists in the high regions of the atmos- 

 phere, the light reflected by clouds at a great heighth 

 has a blue appearance because it traverses a gas of this 

 color. It is so likewise with the light illuminating the 

 distant portions of a landscape. Experiments have 

 shown that 25 milligrammes of ozone for every square 

 centimeter of a layer of 80 kilogr. thick can produce this 

 phenomenon. 



We learn that Prof. H, S. Prichett, Director of the 

 Glasgow Observatory, has been appointed Professor of 

 Mathematics in Washington University, St. Louis, Mis- 

 souri. 



