;66 



NATURE 



[February 15, 1894 



numbers counted as heads, the even numbers as tails. The 120 

 throws were divided into 3 groups of forty in each, and gave 

 the results of all-alike 8, 12, 8, total 28 ; as against not all- 

 alike 32, 28, 32, total 92. The most probable expectation 

 having been 30 to 90. Francis Galton. 



Clerk Maxwell's Papers. 



I DO not know whether the Clerk Maxwell Memorial Com- 

 •iiiittee have ceased from their labours, but I cannot help thinking 

 th it more might be done towards rendering the work of Max- 

 well more readily accessible to students. The pair of ponderous 

 volumes issued by the Committee are very well in their way, 

 but they are certainly bulky, and the chronological order of 

 papers, though eminently suited to their purpose, is not so 

 suited to the practical needs of students. 



For instance, the papers on the kinetic theory of gases seem 

 to me far and away better than much that has been written 

 since, and it would be very convenient to be able to procure 

 them separately. 



My suggestion is, then, that with the aid of a moderate 

 subsidy a publisher be induced to issue Maxwell's papers on 

 special subjects in cheap, handy, separate volumes, which might 

 run somewhat as follows : — 



On Colour and Optics. 



On Graphical Statics. 



On the Kinetic Theory of Gases. 



On Dynamical Problems. 



On Electro-dynamics. 



Lectures and Addresses. 



Articles and Reviews. 



Under one or other of these heads almost all the papers 

 could be included ; there would be no need to include anything 

 that did not seem likely to be of frequent use. The series of 

 .'mall books would be a boon to students, and a knowledge of 

 the work of their great author would be more widely spread, 



Oliver J. Lodge. 



Abnormal Eggs. 



The occurrence entitled " A Curiosity in Eggs," related in 

 Kature for February i, is by no means as unusual as your 

 correspondent imagines. It occurs in domestic poultry from 

 over-stimulation of the system by generous feeding. The explana- 

 tion of the production of one egg within another is very simple. 

 The ovum or yolk when mature is received into the upper part 

 of the oviduct, a tube nearly two feet in length in the domestic 

 fowl, and in its descent is clothed successively with the layers 

 of albumen or white, the lining membrane of the shell, and 

 finally, on arriving at the calcifying portion of the oviduct, is 

 enveloped in the shell. In the ordinary course of events the 

 mature egg is then expelled, but in the case of the production 

 of a double-yolked egg, a reverse action of the oviduct occurs. 

 In place of being expelled, the egg is carried back again to the 

 upperportionof the oviduct, where it meets with another mature 

 ovum, and the two descend together, both being surrounded 

 with a second investing series of albumen, membrane, and shell. 



Some of the occurrences connected with abnormal eggs are 

 very remarkable. I had one forwarded to me during the last 

 month, which was alleged to contain a marble. On examination 

 I found that the supposed marble was a small abortive yolkless 

 egg, which in colour and form, but certainly not in weight, 

 closely resembled a common clay toy marble. It is not unfre- 

 quent for persons to allege the occurrence of various foreign 

 bodies in eggs. The most common substance said to be found 

 in an egg is a horse-bean, which is closely simulated by a mass 

 of hard coagulated blood which has escaped from the ovarium 

 into the oviduct, and is included along with the yolk in the 

 investing structures. I need not further allude to such circum- 

 stances as a horse-hair in an egg, or a small coin not unfre- 

 quently found at the breakfast-table, inasmuch as these are 

 merely the result of practical joking, and require no further 

 explanation. There is, however, one circumstance that may 

 interest some of your physiological readers, and that is the 

 extreme rarity of the hatching of any egg the shell of which is 

 in the slightest degree malformed. In my own experience I 

 have rarely, if ever, found an egg the shell of which was in the 

 slightest degree unsymmetrical, that has been channeled at 

 one end, or having an irregular zone around the middle, to 

 produce a chicken. The occurrence of two ova in the same egg 



NO. 1268, VOL. 49] 



is by no means uncommon. It results from excessive feed- 

 ing, and rarely, if ever, occurs in a state of nature. I have 

 known two perfect birds, both chicken and pigeon, produced 

 from such an egg, but the more general result is that the 

 two ova, being developed together, coalesce, possibly from 

 want of room to develop in the confined space, and thus 

 arises the presence of two-headed, or six or eight-limbed 

 monsters, which are much more frequent in fowls than in 

 any other animals whatever. I have from time to time for- 

 warded specimens of these abnormalities to the museum of the 

 College of Surgeons, where they may be seen by those who are 

 interested in the subject. W. B. Tegetmeier. 



North Finchley. 



On two occasions fully shelled eggs of about the size of those 

 of the thrush have been found by myself within ordinary hen 

 eggs, one of which is still in my possession. Several times I 

 have hatched twin chickens from double-yoked eggs, and once 

 a monstrosity having four legs. 



Shirenewton Hall, Chepstow. E. J. Lowe. 



THE PLEIADES. 



A MONG the many constellations and star clusters 

 -^~^ which attracted the attention of our early ancestors, 

 few, indeed, were so constantly observed as that small 

 bunch of twinkling brilliants known as the " Pleiades." 

 From a very early date, when our forefathers were not so 

 well acquainted with the divisions of the year as we are to- 

 day, they needed some means by which they could tell 

 when to sow their corn, and make arrangements for other 

 agricultural pursuits which could only be done properly 

 in their right seasons. That they could, at any rate, get 

 a rough approximation of such divisions of the year by 

 means of the positions of the heavenly bodies, they soon 

 found out, and they were thus led to observe sometimes 

 stars, sometimes groups of stars, near the rising or setting 

 of the sun, and even certain stars, or groups of stars, at 

 their times of rising and setting. 



That they should have chosen that group of sparkling 

 stars, the Pleiades, to serve their purpose, does not seem 

 at all astonishing if one considers how easily they 

 can be recognised in the sky, and also their important 

 position in more remote times. 



The different relative positions of the sun and the 

 Pleiades had no doubt first attracted special attention 

 to this group of stars, and we know how important a 

 role they played in ancient times for calendar purposes ? 



Let us just consider the several positions of the 

 Pleiades as a result of the earth's rotation and revolution 

 round the sun. Commencing about the end of May, we 

 find that the Pleiades are altogether invisible, as they 

 rise and set together with the sun. As time goes on, they 

 will appear above the horizon before the sun, the differ- 

 ence in the time of rising of these two objects gradually 

 increasing. In August the Pleiades cross the meridian 

 about the time the sun rises, and by the end of November 

 they are visible throughout the whole night, their upper 

 culmination taking place at the same time as the lower 

 culmination of the sun. As November draws to a con- 

 clusion, they set earlier and earlier, and by the end of 

 February are visible only for a short time, disappearing 

 altogether for a time after the middle of May. 



Owing, however, to a slight movement of the axis of 

 the earth, which makes a revolution round the pole of 

 the ecliptic once in about 25,800 years, the point of 

 intersection of the ecliptic with the equator is not 

 fixed but movable ; thus we can understand that the 

 positions of all heavenly bodies as regards their right 

 ascensions and declinations suffer a continual but slow 

 alteration. 



This slow movement explains the reason why the 

 Pleiades have not always been invisible at the end of 

 the month of May, and we have only to form a simple 



