324 



NATURE 



[Fed, 8, 1877 



nearest ai^proacli to the earth in the middle of vSeptember it 

 exhibited a tail 24° in length, according to Baron de Zach ; at 

 this period, though near perihelion, its distance from the earth 

 was I •26. We may conclude that should the comet arrive at 

 its least distance from the sun about the close of the year, its 

 recovery will be almost certain. 



In a future note we shall examine the conditions attending 

 perihelion passage at other seasons. 



The appearance immediately preceding that of 1812 probably 

 occurred about the year 174". The calculated comet of that 

 year had very different elements, and the same remark applies to 

 the tv/o comets of 1743. Struyck mentions a second comet in 

 1742, recorded in the journals of several Dutch navigators. On 

 the morning of April 14, the ship being (at noon) in latitude 

 35° 36' S., and longitude 42° E., the comet was in the E. ^ S.E., 

 with a tail 30° in length ; the time is not given. From this 

 rough indication it may perhaps be inferred that its place was 

 somewhere amongst the stars of Pisces, or bordering ones in 

 Aries ; in too sm.all a right ascension to admit of its identity with 

 the comet of 1812. And as already stated, an examination of 

 earlier cometary records is not attended with more success. 



During the actual revolution there may be very sensible 

 perturbations due to the attraction of the planet Uranus. 



The Zodiacal Light. — This phenomenon was conspicuous 

 in the neighbourhood of London on the evening of the 4th inst. 

 At 6h. 35m. the light was very much stronger than that of the 

 Via Lactea in the brightest part above the horizon, and totally 

 different in colour, being a pale yellow in the more elevated 

 portion, with a ruddy tinge nearer the horizon. It was not dis- 

 tinctly traceable much beyond C Piscium ; the axis of the light 

 passed through about R.A. 352°, N.P.D. 100°, 



BIOLOGICAL NOTES 



Amount of Water in Trees. — Farmers and gardeners 

 have often observed, and the fact is referred to by Lindley, that 

 during cold weather the branches of certain trees are sometimes 

 so much bent down as to obstruct passage below the tree, but 

 that with the advent of mild weather they return to their former 

 positions. In investigating these phenomena, Prof. Geleznow 

 observed that they depend not only upon temperature, but also 

 upon the humidity of the air ; and he undertook, therefore, a 

 series of researches to ascertain the amount of water contained 

 in different parts of the branches under various atmospheric con- 

 ditions. The first part of these researches (not yet published) 

 proved (i) that the amount of water increases in each branch 

 from its base to its summit ; (2) that the bark of the larch 

 throughout the year contains more water than the wood ; and (3) 

 that in Coniferse the upper part, i e., the part above the pith of 

 a horizontal branch, contains always more water than the lower 

 part, whilst in other trees, as, for instance, the birch, the con- 

 ditions are reversed ; altogether, that Coniferge and Dicoty- 

 ledones seem to possess opposite properties, as regards the dis- 

 tribution of water in the tree. Further researches, published 

 now in full {Bull. Ac. de St. PHersh., vol. xxii.. No. 3), intro- 

 duced new elements into the inquiry, namely, the varying amount 

 of water in the bark and the wood. It appears from these re- 

 searches that humidity of the wood and diyness of bark have 

 a constant relation ; that in certain trees (fir and maple) the 

 wood remains throughout the year drier than the bark, while in 

 others (birch and aspen) this is the case only during a part of 

 the year, the conditions being reversed at other times. The 

 relations between the humidity of the bark and that of the wood 

 are so constant, that a useful classification could be based on 

 them. It appears, further, that the smallest amount of water 

 contained by the bi-anches of certain trees, as, for instance, the 



fir, is observed during the season when the vegetation is in 

 fullest vigour, and that this circumstance, as well as some other 

 important facts, is in close relation with the development of 

 leaves. Altogether the researches, which are yet far from being 

 completed, promise to disclose, and probably explain, a variety 

 of very interesting facts. 



The Eel. — In the last session of the Rhenish and West- 

 phalian Natural History Society, O. Melsheimer reported the 

 results of observations on the habits of the eel, conducted 

 through a series of years. The statement that the eel subsists 

 on vegetable nourishment, probably originating from Albertus 

 Magnus, is shown to be utterly false. Examinations of the con- 

 tents of the stomach of numerous individuals show that the food 

 of the eel is exclusively animal. It seems to be especially fond 

 of the river lamprey {Petromyzon fluviatilis). The periodical 

 movements — down stream in August and September, and up 

 stream in April — are brought in connection with the spawn- 

 ing, which takes place in the sea. The bluish-black and the 

 yellowish-green varieties are perfectly alike in their habits. 



HoNEYDEW IN PLANTS. — Prof. Dr. H. Hoffmann, of Gies- 

 sen, has recently published the results of his observations on 

 the formation of honeydew upon the leaves of plants, and 

 has come to the conclusion that it is not to be attributed 

 to the Aphis, or other insects. A healthy specimen of 

 Camellia japonica, \\ feet in height, without blossoms, which 

 afforded an instance of the phenomenon, was found to be en- 

 tirely free from insects. The so-called honeydew consisted of 

 a sticky colourless liquid, which possessed a sweetish taste, and 

 contained, principally, gum. This gradually appeared on the sur- 

 face of the leaves, slowly forming drops on the under-side, which 

 dropped down to be continually replaced. The separation of 

 the liquid continued vigorously for some time, even after the 

 removal of the leaves from the plant. Although showing that the 

 appearance of the dew is not attributable to insects. Prof. Hoff- 

 mann was unable to ascertain the real method of formation. On 

 the upper side he was able to trace the origin of spots of a 

 clear slightly sweet liquid on the leaves of an ivy, to the presence 

 of Coccus sp. This insect, as well as Coccus abietis and pini, 

 seems to possess the power of forcibly ejecting, per anum, a 

 sweetish secretion, which causes them to be sought after by bees. 



Relation of Body-change to Temperature. — From exact 

 experiments on frogs (measuring the consumption of oxygen and 

 production of carbonic acid at different temperatures), M. Schulz 

 arrives at the conclusion that the exchange of materials in these 

 animals is directly dependent on the temperature (Pfliiger's 

 Archiv). It is specially notable, in M. Schulz's tables, that at 

 I'' body-temperature the frog exhales so little carbonic acid that 

 it was hardly certain whether it produced any (the amount was 

 0'oo84gr. per kilo, and hour). At 33° to 35°, on the other 

 hand, the frog shows an exchange of material which comes up 

 to that of man, and at 37° it would probably exceed this con- 

 siderably, if the organism of the cold-blooded animal permitted 

 of so rapid a replacement as the strong consumption would re- 

 quire. The upper limit of temperature for the frog is therefore 

 somewhere about 35° C. 



NOTES 



The city of Brunswick is making preparations to celebrate 

 the looth birthday of Carl Friedrich Gauss, the mathematician 

 and astronomer, who was born there April 30, 1777. A statue 

 is to be erected to Gauss, and it is hoped that the foundation 

 stone will be laid on the celebration day. Contributions are 

 requested by the Committee to be sent to the Brunswick Bank. 



