March 7, 1889] 



NATURE 



437 



version into heat (wasted in space) ; and this, again, is an 

 indication of the relatively small permanence in such a system, 

 before pointed out as a probable fact. If there is not much free 

 gas in a nebula, the heat radiated by the meteoric masses into 

 space xvill be great, because unobstructed by the gas. If, on the 

 other hand, there is much free gas in the nebula, it will fritter 

 thetranslatory motion down by friction into heat. A translatory 

 motion whose temperature equivalent (36,000" C.) is from ten to 

 twenty times more than sufficient to volatilize the moving 

 masses, if utilized, could scarcely exist for a lengthened epoch, 

 or this would seem to be an unnatural state of things. 



If the meteoric masses had a mean length of path at all com- 

 parable in relative scale to that of a gas at normal density ; such 

 as, for instance, if the mean path were (merely for illustration) 

 1000 times the diameter of the meteorite ; then it is evident that 

 the whole system — by a translatory motion of 5 J kilometres per 

 s«cond — would be resolved into gas in a few minutes or even 

 seconds of time. The question then becomes, as it seems, How 

 far does lengthening the mean path diminish the tendency to 

 resolution into vapour by allowing time to cool between the 

 encounters ? or some mechanical relations might possibly be 

 demonstrated here from elements ^ or physical data determinable 

 apparently. S. Tolver Preston. . 



Paris, February. 



Upper Wind Currents over the North Atlantic 

 Doldrums. 



The following observations were taken on board the steam- 

 ship Araucania on her voyage from Liverpool to Valparaiso in 

 December last : — 



From the Cape Verde Islands down to 9° N. lat. the surface wind 

 was steadily north-east, but the low clouds came as persistently 

 from south-east, and the middle or high layers from south-west. 



About 5° N. the wind worked, gradually through east to 

 south-east, and we experienced no calm doldrum, nor even a 

 belt of variable winds. From here to the equator the surface 

 wind remained south-east, while the low clouds came from 

 between south and south-east, but the middle and high layers 

 still passed from south-west. 



From 'the line till about 10° S., while the surface wind con- 

 tinued to blow from south-east, the high cirrus moved from the 

 north-west. 



The circulation of the atmosphere, indicated by these observa- 

 tions, is very different from that described by myself in your 

 columns on two former occasions. On one, while traversing the 

 same track as now, only in the month of July 1885 ; and on 

 another while going from Cape Verde to Cape Town in Decem- 

 ber of the same year, I found the highest current over the 

 doldrums coming from the east. Now there was no doldrum at 

 all, and though there were 200 miles of latitude between the 

 place where the last south-west highest current and the first 

 north-west highest current were observed, it seems somewhat 

 improbable that there was a narrow belt of high-level east winds 

 between these two currents from some point of west. 



It may be noted that cirrus came from the south-west for 

 about 300 miles of southing over the south-east trade, and that a 

 low current from south-east blew over both trades from 6" S. 

 to 13° N. Ralph Abercromby, 



Straits of Magellan, January 15. 



The Giant Earthworm of Gippsland. 



In the last issue of Nature (p. 394) I observe in an article 

 upon Megascolides atistralis that a supposition is expressed that 

 very large earthworms will be found to occur in South America 



' Tt is said that "The total energy of agitation in an isothermal adiabatic 

 sphere is half the potential energy lost in the concentration from a condition 

 of infinite dispersion " (Mature, Nov. 29, 1888, p. 107), This is apparently 

 the analogue of the ratio of Claiisius, somewhat differently extrc'^sed, Viz, 

 the ratio between the two parts of the energy, translational and vibrational 

 (internal motion), applicable to a rigid body, and calculated at J a priori by 

 Maxwell. I would venture one remark here. It appears evident that if the 

 mean thermal equivalent of half the potential energy lost were all accumu- 

 lated in the meteorites, they would be volatilized. If, on the other hand, 

 pare of this thermal equivalent were dissipated in space by radiation, the 

 meleorites could not possess their natural equivalent of thermal energy due 

 to the translatory motion, and consequently it would seem that in the con- 

 tinued effort towards the equ.-ilization of these two forms of energy (trans- 

 latory and thermal), the translatory motion would with tolerable rapidity 

 degrade down to a v.-ilue which could no longer support the weight of the 

 superincunibent material. This would be anjther argument for the small 

 degree of permanence of such a system, 



as well as in other continents. It may be of a little interest to 

 mention that I found near the town of Manaos, in Amazonia, in 

 the year 1874, an earthworm that measured 30 inches in length 

 by \ inch in greatest breadth. When found, in the early morn- 

 ing, it was quite fresh, though newly dead, being .somewhat 

 crushed near one end, probably by some passer-by in the dark- 

 ness. Unfortunately the worm spoiled in the rum in which L 

 attempted to preserve it. James W. H. Trail. 



University of Aberdeen, February 27. 



Weight and Mass. 



Prof. Greenhill seems to have overlooked the fact that my 

 letter in Nature of February 7 (p. 342) related entirely to pro- 

 cedure in teaching. I merely stated that as the result of experi- 

 ence I have found it absolutely necessary to use terms strictly in 

 the senses assigned to them by definition, and not to use the same 

 term in two senses. I find that it conduces to clearness and 

 accuracy to use the word "pound," for example, only in the 

 sense of a certain quantity of matter, and to use the phrase 

 "weight of a pound " when speaking of the force of gravity on 

 that quantity of matter. 



With the ordinary expressions used by engineers when address- 

 ing engineers or other persons who, presumably, are able to 

 distinguish between the different senses in which the same term 

 or phrase is used, I have no quarrel whatever, and must decline 

 Prof. Greenhill's invitation to express an opinion as to the 

 accuracy of the phrases which he quotes from Nature. 



University College, Bangor, February 25. A. Gray. 



The Formation of Ice. 



In connection with the discussion on the formation of ice in 

 crystals, it might be worth while to record that on December 6, 

 1861, in a .slight frost, I saw some in the process of formation in a 

 trough of water. There were three thin pieces of ice in it, two 

 irregular, but the third a beautiful star, 4 or 5 inches in diameter, 

 having six feather-like rays wliich were branched twice or thrice, 

 in all cases at an angle of 60°. Also^ two days before, when the 

 water in the trough was frozen over, I observed in it six-rayed 

 stars several inches in diameter very slightly raised above the. 

 rest of the surface. T. W. Backhouse. 



Sunderland, March 2. 



ROTIFERA AND THEIR DISTRIBUTION} 



IT IS no longer possible, I think, for your President to 

 give, as the substance of his address^ a summary of 

 the most important improvements of the microscope, and 

 of the most remarkable results of microscopical research, 

 which have been recorded in the preceding twelve 

 months. 



All this is now so fully and' so admirably done in your 

 own journal, by your energetic Secretary and his able 

 colleagues, that your Presidents will most probably, in 

 future years, have to follow the excellent precedent set 

 by Dr. Dallinger, and choose for the subject of their 

 address some topic directly, springing from their own 

 special studies. For, on an occasion like this, each 

 President would wish to give the Society the best he 

 can, and it is clear that this best must be sought for 

 among matters of which he has a special knowledge. 



Unfortunately, an accident, which befell me early last 

 year, not only robbed me of the pleasure of being present 

 at several of your monthly meetings, but also produced 

 consequences that compelled me to pirt my microscope 

 aside ; and, as I had not long before finished my share 

 of the " Rotifera," I feared at first that I had lost the 

 power of pursuing any new investigations, just at the very 

 time when I had published the results of all my old 

 ones. 



There is, however, still a portion of my subject with 

 which I am familiar, and which, I believe, has not as 

 yet been touched upon by anyone ; and I venture to 



I .Address delivered at the Annual Meeting of the Royal Microscopical 

 Society, by Dr. C. T. Hudson, President, on February »3, 1889; 



