July 4, 1895] 



NATURE 



22 ■ 



are here illustrated — one a group of four, the other of two ; the 

 latter shows a straight- edged scraper above, conjoined to a simple 

 flake below. 



Hertfordshire conglomerate occurs as a surface stone at the 

 same place, and I have at different times picked up very thin 

 pieces without bulbs which appeared to me to have been artifi- 

 cially flaked. I have, however, kept no disputable objects. 

 I lertfordshire " ])Iuni-pudding stone " was certainly flaked by the 

 Kelts of this district, as is proved by the large, faceted and w ell- 

 bulbed knife-like flake of conglomerate, found by myself at Cad- 

 <lington, here illustrated. This stone is not mentioned as one 



Fig. 3. — Straight edged scraper, conjoined to a flake (half actual size). 



known to have been utilised for tools in the list given by Sir 

 (ohn Evans, in his '• .Stone Implements of Great Britain." 



It is difficult to fi.\ a date for the Romano- British living sur- 

 face here mentioned, as the coin is too corroded for determination ; 

 but a correspondent, the Rev. Henry Cobbe, of Maulden, has a 

 Roman coin, found in an adjoining field at Caddington, inscribed 

 " C. CtSAR Xvc. Germ.\nicis." If this inscription indicates 

 the Emperor Caligxila, as Mr. Cobbe believes, we have a date, 

 A. D. 37-41, and the coin was probably brought over by one of the 



Fi<;. 4. — Larj^c knifc-likc flake of Hertfordshire conglomerate (half actual 

 size). 



soldiers of Aulus I'lautius under Claudius, in the second coming 

 of the Romans in A.I). 43. 



\ short distance from the old land surface here described is 

 an extensive Roman refuse pit w ith abundant broken pottery ; 

 so that it is safe to assume that a Roman villa once stood close by, 

 and we seem to have evidence of the curious fact of a Kelt sitting 

 down in close proximity to a Roman house and its refuse pit, 

 quietly chipping his stone implements. It is equally curious that 

 the implements and detached flakes have remained undisturbed 

 so near the surface for nearly two thousand years. 



Dunstable. Wokthington G. Smith. 



The Bifilar Pendulum at the Royal Observatory, 

 Edinburgh. 



.SoMK interesting readings of the bifilar pendulum, designed 

 by Mr. Horace Darwin for measuring movements in the earth's 

 surface, were made here at noon on the 9th inst. This instru- 



ment, which indicates oscillations in a north and south direction, 

 was erected in March of last year, and daily observation of it 

 has since been carried on, the scale being read off each minute, 

 from five minutes before to five minutes after Paris noon. On 

 the gth inst. nothing unusual was noticed during the first seven 

 readings, these being all practically the same ; but on putting 

 my eye to the telescope for the eighth, I at once noticed 

 that during the interval of less than a minute since the 

 ])receding reading, the mirror had rotated considerably about 

 its vertical axis, the normal having moved towards the 

 north, the difference between the seventh and eighth 

 readings being no less than 7 '6 mm. of the scale. An imme- 

 diate examination of the lamp-stand showed it to be perfectly 

 firm. After the regular daily readings were completed, others 

 were made at intervals of generally two minutes, for half an hour 

 after Paris noon. These showed two quite conspicuous oscilla- 

 tions of the mirror during its return to its original position, which 

 it reached about thirteen minutes after noon. It continued to 

 move beyond this point towards the south, till at oh. 31m. Paris 

 mean time it was 4-1 mm. south of the point at which the scale 

 was first read off. Later readings in the course of the day 

 showed that it was still moving slow ly to the south, but no further 

 oscillations were recorded. In the evening, when the mirror 

 appeared to have come to rest, the sensitiveness of the instrument 

 was tested, and with this the column headed "Tilt of mirror- 

 fraine " in the follow ing table has been computed. The positive 

 sign indicates a tilt to the north. 



Thomas Heath. 

 Royal Observator)-, Calton Hill, i;dinburgh, June 20. 



NO. 1340, VOL. 52] 



Migration of a Water-beetle. 



Last night, at about ten o'clock, a beetle flew in through the 

 open window, alighting on a bowl of roses in the centre 

 of the dining table. On being dropped into a finger-bowl 

 he promptly dived and swam merrily, and jirovcd to be a 

 specimen of the ordinarj' brown water-beetle, to be found in 

 every pond or ditch of water. Now the nearest water to my 

 dining-room w indow is the Thames, distant over a quarter of a 

 mile as the crow flics, w hence this water-beetle must have flown. 

 Can any of your readers inform me whether such long flights 

 have been observed before in connection « ith the pairing .season 

 or migration of this species? I enclose you a rough sketch of 

 the beetle, not know ing its specific title amongst the Coleoptera. 



Rose Haig Thomas. 



Basildon, Reading, June 23. 



