August 23, 1883] 



NATURE 



389 



Apis melli/ica (hive bee) on the above bed confined itself to the 

 mignonette. This remark applies to several individuals. 

 Chester, August 17 Alfred O. Walker 



A Meteor 



A beautiful meteor was seen from this place on Sunday 

 evening, August 19, at 10.3 precisely. Owing to the brilliancy 

 of the moon, i tars of the first magnitude were but faintly seen. 

 I should say the tize and brilliancy of the meteor was greatly in 

 excess of the planet Venus at it. bes f . It was visible as far as I 

 could conjecture about three seconds, and pursued a course of 

 probably 45 or 50 degrees, proceeding from a point a few degrees 

 to the eastward of, and higher than, the north star. It moved 

 almost in a straight line downwards with an inclination to the 

 left. When it had got about half of its w hole visible course, it 

 seemed to get blue in colour, and threw off a mass of red sparks, 

 and continued for the rest of the distance, when it appeared to 

 burst, and the disjected fragments were red and visible for a few 

 moments. The colour for the most part was very much like that of 

 Venus, indeed, for the whole of the course, except where it 

 seemed to turn blue. A. Trevor Crispin 



Lansdowne Road, Wimbledon, S.W., August 21 



I SAW a very brilliant meteor from the promenade here last 

 night (Sunday, August 19), at 10.3 p.m. It passed along the 

 ea-tern sky and vanished over the summit of the Little Orme. 

 The meteor was, I think, more brilliant than Venus at her 

 brightest, though the full moon was shining not far off and very 

 few stars were visible. The path was northward, nearly hori- 

 zontal, inclined a little downward;, about 10° or 12° above the 

 horizon, apparently much foreshortened, for the motion was 

 very slow— 11 it faster than that of balls falling from a rocket ; 

 white light, slightly tinged with blue. 'Ihe meteor divided, and 

 left one large and 1 think several smaller portions behind it, all 

 vanishing t gether. It should have been seen overhead towards 

 thecoistof Vorkshire. Albert J. MorT 



Llandudno, August 20 



Animal Intelligence 



A circumstance exceedingly illustrative of the sagacity of 

 the horse was witnessed by myself in the neighbourhood of 

 Nottingham. I had been out for a stroll by way of recreation, 

 returning home across son e fields by the 1 rent side, and when 

 nearly opposite Clifton Grove I .stop,'e i a shut lime to watch a 

 man angling in the river, when suddenly my attention was dra^n 

 to a mare with her foal, not many yards distant from where I was 

 standing, open two gates which were vice verst^ closing with a 

 strong spring. Her modus operandi was to place her nose in 

 between the two gates and force one ^ate open with her side, 

 while she had no Utile difficulty in opening the other for the pur- 

 pose of getting through. I have learnt that the animal had not 

 been trained to do this, but taught by natural instinct, and so 

 cleverly was it dine that man cojl.l scaicely have performed the 

 action better. Thinking this instance of sagacity might be inte- 

 resting to some of our naturalists, I take the liberty of forwarding 

 same in order that you may insert it in your valuable paper. 



9, Charlotte Street, Nottingham F. WELCH 



Mr H. Cecil's communication respecting the cat and the 

 chicken, at p. 320 of your present volume, reminds me of an instance 

 of the attachment of a cat to its natural prey which is still more 

 remarkable, as there was no ** maternal sropyo " in question. 



Some years ago we had a young emasculated torn cat. When 

 it was nearly full grown we had two young white rabbits brought 

 in which had lost their mother. These were kept in the kitchen, 

 and fed by pouring milk into their mouths with a spoon. They 

 were placed in a basket at night and covered up to protect them 

 from the cat, which was in the habit of catching wild rabbits. 

 One morning the cover was found to have been removed by the 

 cat, which was lying in the basket with the little rabbits. From 

 that time he took charge of them, teaching them to lap milk and 

 watching over them like a mother, even to the extent of driving 

 them home when they grew older and rambled out from the 

 kitchen. The friendship continued till the rabbits grew up, 

 when we lost them by disease. Alfred 0. Walker 



Chester, August 17 



" Birds and Cholera " 



In refererence to " H. M. C's. " letter in this week's Nature 

 (p. 366), it is interesting to recall how the traveller Jackson, 

 speaking of the plague that occurred in West Barbary when he 

 was there, says, " The birds of the air fled away from the 

 abodes of men." Thomas Maore, in "Paradise and the Peri," 

 refers to this fact. E. S. T. 



August 18 



LIQUID FILMS AND MOLECULAR 

 MAGNITUDES 



C IR WILLIAM THOMSON'S lecture on " The Size of 

 *-* Atoms," which has recently been published in 

 Nature, will undoubtedly increase the interest felt in 

 measurements which throw any light upon the values of 

 molecular magnitudes. 



Ws have for some time been engaged in investigating 

 the properties of very thin liquid films, and in our last 

 communication to the Royal Society (of which only an 

 abstract has been hitherto published, but which will appear 

 in a forthcoming number of the Philosophical Transac- 

 tions) we have described two independent methods by 

 which we have obtained concordant measurements of 

 the thickness of soap films in the last stage of tenuity, 

 viz. when exhibiting the black of the first order of Newton's 

 rings. 



The paper had not been sent in to the Royal Society at 

 the time when Sir Win. Thomson's lecture was delivered, 

 but, on receiving the abstract, he has been good enough 

 to express his approval of our methods and interest in our 

 results, and to raise some cpuestions as to the relation 

 between the observations of Newton and ourselves, the 

 further discussion of which he thinks would be interesting 

 to the readers of Nature. 



We propose therefore briefly to discuss the facts which 

 bear upon the points raised by Sir Win. Thomson, and to 

 describe our methods of experiment so far as may be 

 necessary to make the discussion intelligible. 



For thLknesses greater than those which correspond 

 to colours of the first order, the tint displayed affords to a 

 practised eye (when co rsbined with a knowledge of the 

 angle of incidence and refractive index) a very accurate 

 measure of the thickness of a film. In some experiments 

 of our own, in which on more than 500 occasions two 

 independent but simultaneous measures were made of 

 lilm-thicknesses by means of two beams of light, incident 

 at different angles, we found that the two values obtained 

 agreed to within 1 per cent, in 52 measures out of every 

 hundred, to within 2 per cent, in S4, and to within 3 per 

 cent, in 95. All these observations were made in the 

 second and higher orders. The colours of the first 

 order vary from point to point too slowly to enable trust- 

 worthy estimates of the thickness to be made, and 

 when the black of the first order is reached the eye 

 informs us only that the thickness must be less than a 

 certain value, but affords no further indications as 

 to what it really is. The fact that it is extremely 

 small, and the possibility that it may be related to the 

 magnitude of the so-cailed "radius of molecular attrac- 

 tion," invest the problem of the determination of this 

 thickness with special interest. We have succeeded in 

 solving it by two methods. In each an assumption has 

 to be made for which there is no direct experimental 

 evidence. In each case, however, the assumption is 

 different, and the fact that the mean results obtained by 

 the two methods are in close accord is sufficient to show 

 that, although there is still room for further inquiry, the 

 mean thickness of the bla:k soap films examined was cor- 

 rectly determined to within a fraction of a millionth of a 

 millimetre. 



The first method consisted in measuring the electrical 

 resistance of a cylindrical black soap film, and deducing 

 the thickness from Ohm's law, on the assumption that the 



