June 6, 191 8] 



NATURE 



271 



allowing the luminous ray to be perceived. The 

 observer at the sighting device can thus read the 

 signals transmitted, in dots and dashes, in the form 

 of short or long light-ravs projected bv the illuminated 

 slit. 



The Leeds automatic telephone exchange, which was 

 ' opened on May i8, is the largest automatic exchange 

 j in Europe. Sir William Slingo, the head engineer of 

 i the Post Office, was one of the first to recognise that 



■ the manual operators in an exchange will ultimately 



■ have to be replaced by automatic devices. The longer 

 the development is delayed, the more capital will be 

 lost when the manual exchanges have to be scrapped. 



■ The Post Office has been criticised for carrying on 

 the work in war-time, but the need was urgent, and, 

 besides, the manual instruments displaced at Leeds 



; were most useful for war service at the front. The 

 ! Leeds exchange is equipped for 6800 subscribers, but 

 it will ultimately have a capacity for 15,000. It repre- 

 sents the very latest developments in automatic work- 

 ing. A storage battery in the exchange supplies the 

 ; energy required for the working of all the switches. 

 \ The definite and accurate working of all the necessary 

 \ switches when any subscriber takes his telephone off 

 the hook and operates his dial is perfect. When the 

 "called" subscriber is engaged the "busy back" signal 

 is sent automatically, and the subscriber has to wait 

 before he calls again. As there are 26,000 wires enter- 

 ing the building, the arrangement of all the connec- 

 tions is a marvel of ingenuity. The Post Office has 

 several other automatic exchanges in this country. 

 The next largest is at Portsmouth, which has 5000 

 subscribers alreadv connected and an ultimate capacity 

 of 7000. 



In a recent letter to the Times (May 27) the Duke 

 of Montrose pleads for moderation in the destruction 

 of rooks. His lordship has examined thirty gizzards of 

 birds shot between April i and May 31, twenty of 

 which contained worms and grubs, six had grains of 

 oats and other matter, one beetles and worms, and 

 one horse-manure and grit. The fallacy, however, of 

 judging of a bird's feeding habits by examining the 

 food content of the stomach during certain periods of 

 the year has frequently been dwelt upon, and just as in 

 this case it would lead the uninitiated to pronounce 

 a verdict in its favour, in regard to other species it 

 would lead us to condemn updoubtedly beneficial 

 species. Whilst not wishing to see the rook exter- 

 minated, experience shows that it certainly requires 

 reducing in numbers. An investigation, now extend- 

 ing over four years, on the food of the rook, 

 during which period upwards of 2000 birds have been 

 examined, shows that of the total food eaten in a 

 year, 35- 1 per cent, consists of cereals, 134 of potatoes 

 and roots, 6t of miscellaneous vegetable matter, 44 of 

 weed seeds, 239 of injurious insects, 35 of beneficial 

 insects, 46 of neutral insects, 32 of slugs and snails, 

 * ^^-4 of earthworms, and 14 of eggs, mice, etc. In 

 other words, 52 per cent, of the rook's food is in- 

 jurious, 19-5 neutral, and 28-5 beneficial. It is, there- 

 fore, impossible to ignore the fact that at present this 

 bird does considerably more harm than good, and that 

 there is now overwhelming evidence to this effect 

 which it would be foolish for the farmer to ignore. 



Spring has closed with a burst of brilliantly fine 

 weather, and May almost throughout maintained its 

 usual characteristic of fickleness. The first half of 

 the month was cooler and the rainfall was generally 

 heavier than in the latter part of the month. At the 

 commencement of May the cold was greatest in Scot- 

 land, the weekly weather report, ending May 4, show- 

 ing the deficiency of temperature to be 4° F. in .Scot- 



NO. 2536, VOL. lOl] 



land E. ; at Greenwich the deficiency was only 1-4°. 

 For the week ending May 11 the temperature was not 

 very different from the normal in any part of the 

 British Isles, and at Greenwich there was an excess 

 of 1-6° F. For the week ending May j8 temperature 

 had an excess of 53° at Greenwich, and for the week 

 ending May 25 an excess of 62°. The highest tem- 

 perature at Greenwich was 83° on May 21, whilst at 

 Camden Square the thermometer registered 88°, and at 

 Tulse Hill 87°. At the latter station the mean tem- 

 perature for May was 58°, the mean maximum was 

 68°, and the mean minimum 48°. The mean maxi- 

 mum temperature for May i to 15 was 62°, and the 

 naean maximum for May 16 to 31 74°, whilst the 

 mean minimum was respectively 46° and 51°. Tem- 

 perature this year in May is nearly as high as last year, 

 and is about 4° above the normal. An absolute maxi- 

 mum of 83° has frequently been beaten for May at 

 Greenwich, but there has been no record as high 

 as 88°. 



We have received from the Rev. S. Graham Brade- 

 Birks descriptions of a curious cloud effect which he 

 has observed over Darwen Moor, Lancashire, the point 

 of observation being in the town of Darwen, to the 

 east of the moor. The effect consisted of a thin 

 stratum of cloud which appeared to run parallel to 

 the contour of the hill of the moor for a considerable 

 distance from south to north. The cloud was noticed 

 on two separate Occasions, viz. on May 6, at 9.30 p.m., 

 and on May 17, at 10-15 p.m., summer time. On the 

 first occasion the sky was otherwise cloudless ; on the 

 second the stratum of cloud was superimposed upon 

 a background of cumulo-nimbus cloud, in the western 

 sky, from which rain afterwards fell. On both occa- 

 sions there was a light N.W. or W.N.W. wind at the 

 surface at lop.m., summer time, which had succeeded 

 a light or moderate S.S.E. wind at 10 a.m. The 

 weather-maps for the two occasions present some 

 points of similarity. On May 6 Darwen was situated 

 in the col or "saddle" between two "highs" and two 

 "lows"; on May 17 it was in the corner of a north- 

 easterly extension of an anticyclone — that is, just on 

 the high side of a "saddle." In such circumstances 

 pilot-balloon observations have frequently revealed the 

 existence of two distinct currents of air superimposed 

 one upon the other, one current conforming with one of 

 the barometric systems, and the other with the system 

 on the opposite side of the place of observation. The 

 sequence of wind observations at the surface would 

 support such a view for these occasions. The bounding 

 plane between the two currents would be a region 

 where stratus clouds, due to mixing of moist air of 

 different temperatures, would be liable to form. There 

 may be some feature of the. Darwen Moor which would 

 locally facilitate such a process. 



At the suggestion of the Palestine Exploration 

 Fund, an organising committee has been constituted 

 by the British Academy with the object of founding a 

 British School of Archaeology at Jerusalem. The 

 committee, in a memorandum just issued, points out 

 that while ArAerican, French, and German schools of 

 archaeology existed in Jerusalem before the war, this 

 country possessed no such institution. It is proposed 

 to establish a school to be devoted, both by excava- 

 tion and surveying, to the furtherance of Palestinian 

 archaeology in all its branches. In addition to Hebrew 

 and Jewish sites and antiquities, the school would 

 include within its scope the Canaanite. Graeco-Roman, 

 Bvzantine, Arab, and Medieval periods. An essential 

 part of the scheme is that the school should be not 

 only an excavating body, but also a training school 

 for archaeologists. It is hoped that universities, col- 

 leges, other institutions, and private patrons will pro- 



