i6 



NATURE 



[October 19, [gn 



that is, 53 days mure- than the average number of hot 

 days per year, it is evident that the method will seldom 

 give results that are useful. 



I think the most striking fact brought out by the 

 diagram is that a distinct relationship exists between the 

 total number of hot days in five consecutive years and the 

 difference between that number and the corresponding one 

 for the next five years. I have used the diagram to find 

 the coefficient of correlation between these quantities, and 

 1 find that its value is as high as —0-725 ±0059. 



Five hot years are thus usually followed by five cold 

 years, and vice versa. This may be accounted for by 

 supposing that the number of hot days at Greenwich is 

 subject to a regular fluctuation with period not far from 

 10 years. If the period were exactly 10 years the 

 coefficient of correlation would be nearly — 1, and all the 

 dots would practically lie on a straight line passing through 

 the origin of the diagram. The fact that they do not lie 

 on a straight line means either that there is another period 

 or periods superposed, or that 10 years is nearly, but not 

 quite, the true period. 



It would be interesting to learn whether the directions 

 of the lines joining successive points (chronologically) on 

 the diagram show any sort of regularity. If they proceed 

 generally in a clockwise direction they indicate that the 

 period is slightly greater than 10 years ; if in a counter- 

 clockwise direction the period is less than 10 years. The 

 whole arrangement is similar in some respects to Dr. 

 Schuster's well-known periodogram. R. Corless. 



October 14. 



Insects Feeding on " Slime Flux " of Trees 



My attention has been directed to three elm trees at 

 Ettington, near Stratford-on-Avon, which it is said have 

 been " killed by wasps." It appears that the wasps were 

 attracted by the sweetness of the sap, and attacked the 

 trees in such swarms, and so drained them of sap, that 

 the death of the trees seems imminent, all the leaves having 

 gone yellow long before the usual time. 



I should be glad to know if others have noticed similar 

 attacks on elm trees, and whether the averred sweetness 

 of the sap is due to some previous degenerative change in 

 the tissues of the tree, or whether wasps would attack a 

 normal tree if they could get access to the sap. 



The elms are all three comparatively young trees, and 

 belong to the common variety. My informant tells me that 

 he has previously noticed the same thing happen with an 

 elm tree in one of his fields, which died the next winter. 

 Joseph A. Gillett. 



Woodgreen, Banbury, October 9. 



A similar phenomenon may be seen at the present time 

 in the collection of elms at Kew. The trunk of a fine 

 specimen of Vlmus parvifolia has for some weeks past — 

 but more especially during August and September — been 

 the daily rendezvous of hundreds of wasps and bluebottles. 

 As is the case with the trees at Ettington, the attraction 

 is the sweet sap that exudes from the trunk. It is a 

 mistake, however, to blame the wasps for the damage that 

 is being done to the trees. They do not cause the outflow 

 of sap, but are merely there feeding on it. A piece of bark 

 has been removed from the tree at Kew and microscopic- 

 ally examined. It was found to be suffering from what is 

 commonly known as "slime flux," the bark being 

 saturated with sugary moisture. The primary cause of 

 this somewhat obscure disease appears to be a yeast, which 

 is way to the cambium layer by means of a wound. 

 Often, as in the Kew instance, ingress has been facilitated 

 by the borings of an elm beetle. The yeast sets up a 

 decomposition of the cells, and starchy, ultimately sugary, 

 products are formed, which exude from the trunk in solu- 

 tion. It is this which attracts the multitude of wasps, blue- 

 bottles, and other insects. It is evident from the odour 

 of the bark that a certain amount of fermentation is 

 going on, and the presence of alcohol is further indicated 

 behaviour of the wasps, which, after feeding for 

 some time, become stupid and lethargic. 



Although " slimp flux " is not an uncommon disease of 

 trees in Britain (it is much more prevalent on the Con- 

 NO. 2 I QO, VOL. 87] 



tinent), it is not one of the most troublesome. Mill, where 

 it attacks it is nearly always ultimately fatal. The Kew 

 tree is evidently suffering from severe debility. Un- 

 fortunately, the disease, as a rule, has beconi. firml 

 lished before there are any outward indications of its exist- 

 ence. When noticed on a branch the part attacked can be 

 removed, but when the trunk is badly affecti d there seems 

 to be no means of curing it. W. J. B. 



Meteor Showers. 



Tin: following meteor showers become due about the 

 time when the Orionids may be expected to put in an 

 appearance : — 



Epoch October 18 22I1. (G.M.T.), approximately twenty- 

 ninth order of magnitude. Principal maximum, October 20 

 i2h. 45m.; secondarv maxima, October 20 nh. 15m. and 

 October 22 Sh. 10m. 



Epoch October 20 9I1. 30m., approximately fifth order 

 of magnitude. Principal maximum, October 21 nh. 15m.; 

 secondarv maxima, October 20 9)1. 30m. and October 22 

 ioh. 35m. 



From the foregoing it may be seen that there is likely 

 to be a considerable amount of meteoric activity on the 

 nights of October 20-22. These three nights seem well 

 favoured as regards maxima, which occur at times very 

 suitable for observations. 



Other radiants besides that in Orion may be found 

 active on the nights mentioned, but Orionids ought to 

 prove most numerous on the night of October 20, as it is 

 on this night that the general Orionid maximum becomes 

 due. John R. Henry. 



October 16. 



The Possible Identity of the Kiess Comet. 



It is well known that the aphelia of many coi 

 grouped at distances which are nearly the same as those 

 of the larger planets, and astronomers have sometimes 

 attempted to use this fact to demonstrate the existence of 

 a planet beyond Neptune. M. Flammarion mentions two 

 cases — a comet which appeared in 1532 and 1661, and 

 Tuttle's 1862 comet, which is related to the Perseid 

 meteors, and has a period of I2ii years. These are taken 

 as indii niions of a planet at a mean distance of about 

 48 astronomical units. The evidence is obviously in- 

 sufficient ; and special interest therefore attaches to the 

 statement that the Kiess comet (1911b) is possibly the 

 same as 1790 I. If the identity can be established, this 

 comet must belong to the same group as the other two, 

 and may be regarded as strengthening their evidence as to 

 the hypothetical planet. P. H. I 1 



7 Chandos Road, Redland, Bristol, October 2. 



Standard Time in New Zealand. 



I note that in Nature of March 16, in an article headed 

 "Standard Time in France," it is stated on the authority 

 of " Hazell's Annual " that the standard time adopted in 

 New Zealand is 11 hours fast on Greenwich. 



This is not correct. New. Zealand standard time is the 

 time of the meridian 172 J° E., that is, 11J hours in advance 

 of Greenwich civil time. This is correctly stated in 

 " Whitaker's Almanac." 101 1, p. So. 



G. Ho 



Sei hi lo cal Observatory, Wellington, New 

 /.' ;il 1, v ' pti mber 4. 



Habits of Dogs. 



Mi;. Yenables's reference to formic acid 



21, p. 3S2) reminds me that once, in the pine- 

 woods at Potsdam, I came upon a forester performing 

 some curious evolutions, apparently patting something on 

 the ground and then holding his hands to his fai Hi 



that it v, as .in ant-hill, and tie- smell v a 

 good for the m A. 1 



