114 



NA TURE 



[JULV 21, 192. 



Aberdeen and in the Shetlands, all on the continuation 

 of this line, were not improbably related to the same 

 general cause, though the continuity of the advance 

 of the original system cannot be verified. 



The main rainfall was confined to a belt between 30 

 and 40 miles in width, lying along the track of the 

 storm. In this zone, falls were probably everywhere 

 greater than i in., at least as far north as the Wash, 

 while they equalled 2 in. in many places, and reached 

 3 in. in isolated patches. On the south coast this belt 

 of heavy rain extended from a point between Worthing 

 and Brighton to a point between Eastbournip and 

 Hastings, while central London lay in the middle of 

 the affected zone. Outside this band, amounts fell 

 off quickly, particularly on the eastern side, where the 

 boundary was sharply defined ; for example, while 

 Eastbourne received ij in., Hastings and places 

 further east escaped rain, and while Tunbridge Wells 

 experienced nearly an inch, there was none at Maid- 

 stone. 



Over the southern portion of the track, including 

 London, rain fell practically continuously for more 

 than 6 hours, so that, allowing the speed of 25 miles 

 per hour, the main travelling rain system responsible 

 for this belt of precipitation was here probably about 

 150 miles long in the direction of its motion, and 35 

 miles broad. 



In the north, the amounts and duration of rainfall 

 appear to have been rather less than in the south of 

 England. 



Striking agreement in time is shown by the hyeto- 

 graph and microbarograph records at South Kensing- 

 ton between sudden changes of pressure and intense 

 bursts of rain, particularly just after 2 a.m. (G.M.T.). 

 There is also agreement between the sudden changes 

 of pressure at South Kensington and those recorded at 

 Kingsway, London, W.C.2, by the Dines float baro- 

 graph, which shows the absolute magnitude of the 



pressure changes. It is interesting to mention that 

 an observer in Hampstead noted quite independently 

 that the worst crashes, followed immediately by 

 torrential rain, occurred at 2.15 a.m. and 3.45 a.m. 

 (G.M.T.). The first of these was about 10 minutes 

 after the occurrence of the very pronounced peak 

 in the Kensington microbarograph record and cor 

 responding heavy rain shown by the hyetograj)li 

 record. Thus, allowing 4 miles between the phn < s 

 of observation, we again find phenomena associ- 

 ated with the storm travelling at about 25 miles 

 per hour. 



Although a closer investigation is desirable before 

 putting forward an explanation of the storm with full 

 confidence, an examination of the weather charts and 

 upper air data available brings to light some very 

 suggestive facts. Measurements of upper winds on 

 the evening before the storm show that between about 

 6000 feet and 18,000 feet above the surface there was 

 a general wind current over the affected area agreeing 

 very closely indeed in direction and speed with those 

 of the movement of disturbance itself, and observa- 

 tions of the drift of cirrus cloud show that above this 

 the air motion was probably from about S.W. Now 

 the weather charts for July 8 and 9 show an anti- 

 cyclone over the Continent and a depression almost 

 stationary off the West of Ireland, and, further, a 

 current of air of undoubtedly polar origin, and there- 

 fore probably having a low upper-air temperature, 

 circulating round the latter. 



It seems very likely that some of this polar air, in 

 arriving, at some upper level, over the south-west 

 districts of England and endeavouring to work its 

 way northwards, side by side with the very warm air 

 of continental origin over the eastern districts, spread 

 laterally over the latter, producing the travelling ar»a 

 of instability necessary to explain the phenomena 

 described above. M. A. Giblett. 



The Pascal Commemoration on the Puy de Dome. 



T^HE tercentenary of the birth of Blaise Pascal 

 -*■ (born June 19, 1623, died August 19, 1662) was 

 celebrated at Clermont-Ferrand in a series of fetes at 

 which the President of the French Republic, M. 

 Millerand, and the most distinguished French scholars 

 and philosophers met to do homage to his great genius. 

 The culminating interest of the celebrations was 

 the visit to the summit of the Puy de Dome on 

 Sunday, July 8, to commemorate the experiment 

 devised by Pascal and carried out successfully by his 

 brother-in-law Florin Perier, an experiment as famous 

 in its day and as decisive in its significance as the 

 eclipse expedition of May 191 9 has proved to be in 

 our day. In demonstrating that the atmosphere has 

 weight it destroyed a principle of the old physics 

 which had become authoritative, the principle that 

 Nature abhors a vacuum, and at the same time it 

 inaugurated a new scientific concept in physics. 

 The rain poured as we gathered on the summit where, 

 above the ruins of an ancient temple of Mercury, a 

 modern meteorological observatory has been erected. 

 Those who were so fortunate as to find room in the 

 small cupola of the observatory, however, are not 

 likely to forget M. Painleve's discourse. Round the 

 President were grouped the Prefects of the Depart- 

 ments, the Mayor of Clermont, the Rector of the 

 University, Senators and Deputies, the representatives 

 of the Institut de France, and the foreign guests of the 

 Municipality. In an eloquent oration M. Painleve 

 described the inception of the great experiment and 

 discussed its significance. 



No one of that large company (the Municipality 

 entertained three hundred guests at the dejenyier 

 on the mountain) who had ascended the mountain by 

 the modern means of electric traction with luxurious 

 comfort in little more than an hour can have 

 failed to reflect on the different conditions which 

 prevailed in Pascal's time, and on the enormous 

 difficulties of the original expedition. Those who 

 are interested may read the full and careful report of it 

 in Perier's letter to Pascal. It was arranged that first 

 of all two sets of apparatus should be tested side by 

 side to see that they gave identical measurements, 

 that is, to see that each column of mercury in the 

 inverted tubes (barometer tubes) remained at the 

 same height. One set was then carried up to the top of 

 the mountain and the other left behind in the church 

 of the Minimes at Clermont. The experiments with 

 each set were made at the prearranged: hour and pre- 

 cisely recorded. The significance of the experiment 

 was its uniqueness. It differed entirely from observa- 

 tions which any one might make with the scientific 

 intention of recording facts ; it differed entirely, 

 for example, from observations such as those of Tycho 

 Brahe. It was uniquely designed to test a physical 

 theory which would stand or fall by the result. It 

 had been known practically by engineers for a long 

 time that there was a natural limit to the action 

 of a pump, and in the crucial experiment of 

 Torricelli with the column of mercury in the glass 

 tube closed at one end and immersed in liquid 

 at the other it was shown that the principle was 



NO. 2803, VOL. I 12] 



