i6 



HARDWICKE'S SCIENCE-GOSSIP. 



obtained was that for purposes of accurate measure- 

 ment, a field of 4 deg. might be used, and a field 

 °f 5 deg. where only approximately accurate results 

 are required. 



On January 28th, there will be visible a total 

 eclipse of the moon, beginning at 9.30 p.m. 



Meteorology— Ax the Royal Observatory, Green- 

 wich, the highest reading of the barometer for the 

 week ending 19th November, was 30-22 in. on 

 Wednesday morning, and the lowest 29-11 in. on 

 Saturday morning. The mean temperature of the 

 air was 34-1 deg., and 7-6 deg. below the average. 

 The general direction of the wind was east and 

 north-east. Rain fell on two days of the week, to 

 the aggregate amount of 0-53 of an inch. The 

 duration of registered bright sunshine in the week 

 was 11 -o hours, against 13-7 hours at Glynde-place, 

 Lewes. 



For the week ending 26th November, the lowest 

 reading of the barometer was 29-17 in. at the 

 beginning of the week, and the highest 29-84 in. on 

 Wednesday evening. The mean temperature of the 

 air was 38-7 deg., and 2-3 deg. below the average. 

 The general direction of the wind was north-east. 

 Rain fell on four days of the week, to the aggregate 

 amount of 0-31 of an inch. The duration of 

 registered bright sunshine in the week was o - 2 of 

 an hour, against 2*7 hours at Glynde-place, Lewes. 



For the week ending 3rd December, the lowest 

 reading of the barometer was 29-47 in. on Tuesday 

 morning, and the highest 30-31 in. on Friday 

 morning. The mean temperature of the air was 

 43 '3 deg., and 1-9 deg. above the average. The 

 general direction of the wind was south-west. Rain 

 fell on three days of the week, to the aggregate 

 amount of 0-48 of an inch. The duration of 

 registered sunshine was 7-4 hours, against 11 • 1 

 hours at Glynde-place, Lewes. 



For the week ending 10th December, the highest 

 reading of the barometer was 29*86 in. at the 

 beginning of the week, and the lowest 29-13 in. on 

 Thursday evening. The mean temperature of the 

 air was 40*4 deg. and 2 - 2 deg. below the average. 

 The general direction of the wind was westerly. Rain 

 fell on four days of the week, to the aggregate amount 

 of 0*47 of an inch. The duration of registered bright 

 sunshine in the week was 2-9 hours, against 9-1 

 hours at Glynde Place, Lewes. 



January is the coldest month in the year. The 

 mean temperature at the Land's End is 45 deg., 

 while in the plain of York it is only 38 deg., the 

 difference being due to the influence of the Atlantic. 

 Travelling from south-east to north-west, the mean 

 temperature of some of the principal towns is 

 approximately as follows :— Truro, 44 deg. ; Ply- 

 mouth, 43 deg. ; Exeter, 42 deg. ; Dorchester, 41 

 deg. ; Portsmouth, 40 deg. ; and London, 39 deg. 



The average rainfall in January is 5 inches from 



the Land's End nearly to Exeter ; 4 inches in Devon 

 and Dorset ; 3 inches along the South Coast and 

 through the greater part of the south of England, 

 from Bristol to Canterbury ; 2 inches through 

 Cheshire and the Midlands to the Essex coast ; and 

 only 1 inch along the East coast from Newcastle to 

 Ipswich. 



GOSSIP ON CURRENT TOPICS. 

 By W. Mattieu Williams, F.R.A.S., F.C.S. 



BUYS-BALLOT— On the 16th of November last, 

 the University of Utrecht worthily instituted a 

 festival in honour of the fortieth anniversary of the 

 "doyen des meteorologistes," M. Buys-Ballot, at the 

 same time founding a prize of a gold medal to be 

 given every ten years for memorable work in meteor- 

 ology, the first, of course, being then given to the 

 venerable professor. 



This is not the place for a sketch of Buys-Ballot's 

 life-work, and if it were, it should be drawn by some 

 one knowing more of the subject than I do. But 

 there is one simple and important generalisation to 

 which his name is attached that should be better 

 known than it is among us here. I allude to "Buys- 

 Ballot's law " concerning the winds and barometric 

 gradient. This gradient has more to do with weather 

 prediction than the height of the barometer at any 

 particular place. If the barometer be either high or 

 low or medium at such place, and of nearly the same 

 height at other places all around, immediate change 

 may be expected ; but if that place be in a steep 

 barometric gradient, i.e. if the barometer is much 

 higher or lower at other places beyond it, a change 

 is imminent. 



If the barometer at a given time stands one-tenth 

 of an inch higher at Edinburgh than at London (both 

 corrected to sea-level), there is a moderate gradient ; 

 with a difference of half an inch there is a steep 

 gradient, indicating unsettled and stormy weather. 

 These gradients may be easily traced on the weather 

 charts published by some of the newspapers. The 

 curved lines, usually dotted, are isobars, or lines of 

 equal pressure, against which are marked the height 

 of barometer all along that line ; the direction of the 

 wind is marked by arrows. 



Buys-Ballot's law, in the northern hemisphere, is 

 that, if you stand with your right hand towards the 

 region of higher barometer, and your left hand 

 towards lower barometer, the wind will blow against 

 your back ; or vice versa, if you stand with your back 

 to the wind, the barometer gradient is ascending on 

 your right and descending on your left, or the 

 opposite if you face the wind. You may test this 

 law by taking such imaginary positions on one of the 

 weather charts, and observing the relations of the 

 arrows and isobars to yourself. 



