Feb. 3, 1887] 



NAIURE 



There was no rain at Rotorua between the 5th and the 

 eruption, tut it rained on the 9th at Wairoa and at 

 Ateamuri, on the Waikato. 



At Rotorua the slight mud-shower fell in directions 

 from south-ea^t to south-west, but most from the south- 

 east, as ascertained by an examination of the telegraph 

 poles. At Taheke, on Lake Rotoiti, the mud must have 

 fallen with a south-south-east wind. At Galatea, eighteen 

 miles east-south-east from Rotomahana,no mud fell ; but 

 the scoria was thicker on the north-west than on the 

 south-east side of the houses : evidently no strong wind 

 was blowing. 



The night of the 9th was calm and fine. During the 

 earlier portion of the eruption there was a slight south- 

 westerly wind at Wairoa, which increased to a strong gale 

 at 3 a.m. ,\t Rotorua there was a slight south-easterly wind 

 up to 4 a.m., when the south-westerly gale reached there 

 from Wairoa. .'\t Taheke, on Lake Rotoiti, the wind 

 changed to south-west at 9 a.m , but there was no gale. 

 At Napier a southerly gale commenced at 4 a.m. ; at 

 Gisborne, in Poverty Bay, a south-westerly gale was 

 blowing ; at Waiapu a strong north-westerly wind was 

 blowing from 3.15 a.m. to 4.30 a.m., when it changed to 

 the south-west. At the East Cape there was a strong 

 southerly gale. It appears therefore that the south-west- 

 erly gale at Wairoa had no direct connection with the 

 eruption, for it commenced about the same time all over 

 the east coast from Napier to the East Cape. 



I was surprised to find that the eruption had caused no 

 great atmospheric disturbance, except in its immediate 

 neighbourhood, and that there was no evidence at all of 

 any indrawing currents. The reason for this, no doubt, 

 is that the area over the openings which was violently dis- 

 turbed is small, so that equilibrium was restored at very 

 short distances around. Eor this reason a volcanic erup- 

 tion has none of the effects of a cyclone. The eruption 

 was, as usual, the cause of much electrical disturbance, 

 but this did not affect the weather. F. W. Hutton 



A FEW OF OUR WEATHER TERMS 



A RECENT skirmish in the Tiiius, on certain words 

 -'*■ in common use among English meteorologists, and 

 prevalent in our weather reports, suggests that a little 

 overhauling of these and similar terms may be from time 

 to time desirable. In a branch of knowledge which, 

 simultaneously with its growth, becomes more and more 

 popular, new terms expressive of new ideas should not 

 only be accurately descriptive of facts, but should be 

 adapted to popular imagination. 



If we cannot have such terms as " helix " and " ant- 

 helix," the Meteorological Department cannot be on safer 

 ground than in their adoption of the terms " cyclone " 



•id "cyclonic," "anticyclone" and " anticyclonic " ; 

 ' se words being precisely antithetical, and expressive 



I phenomena which are the opposites of each other in 

 .dinost all their characteristics. To both of these words, 

 however, objections have been raised, and these objec- 

 tions have been somewhat inconsistently based on differ- 

 ent reasons. The word cyclone has been objected to 

 because it terrifies our women ; but its equivalent, " re- 

 volver," would produce at least as alarming an effect. 



they would soon, however, get accustomed to the use of 



either. The most unscientific people will quickly under- 



\nd that when the laws which govern a particular kind 



■ atmospheric circulation have once been proved to be 

 '■ntical, whether that circulation bj violent, moderate, 



feeble, it becomes desirable to have a single term 



■ icriptive of such a circulation. Such nouns as " hurri- 

 ne,"' ''storm," &c., can be employed, if we please, 



to denote that the disturbance is of a violent or severe 

 character ; while we have plenty of adjectives, strong 

 or mild, to be employed at discretion. Perhaps this 



will be still more fully realised when the public un- 

 derstands that, in any particular instance, the circulat- 

 ing winds may vary between the most violent and 

 the lightest during the progress of the disturbance. As 

 .Mr. Abercromby clearly stales it : " The same cyclone 

 may develop the energy of a hurricane soon after its birth 

 in the West Indies, and, after a long and stormy life in 

 its passage across the Atlantic, die surrounded by gentle 

 summer winds on the rocky coasts of Norway." The 

 original use of the term "cyclone" was almost limited to 

 the phenomenon in its acutest stage ; and, owing partly 

 to this fact, meteorologists have been disposed to apply 

 the expressions " cyclonic system " and " cyclonic dis- 

 turbance," &c., to the gentler instances or stages of this 

 kind of circulation, rather than the word " cyclone" itself; 

 but the latter word might now be used without hesitation, 

 for it is most true that " a progressive science uses words 

 provisionally to express provisional ideas, and as the ideas 

 increase in clearness and precision " (and, we may add, in 

 extension) "the word has to take on new meanings." 



The term " anticyclone " has been recently objected to 

 as possessing absolutely no significance, an objection 

 which is not in itself worthy of discussion in these pages. 

 This objection is, however, probably founded on one of a 

 more serious nature, viz. that anticyclones are merely 

 interspaces between cyclones. Such interspaces do, of 

 course, exist, and they occasionally travel on without 

 undergoing any very rapid change of form in company 

 with the cyclones. But the interspaces between circles or 

 ovals are not circular or oval ; and further (as is more 

 important to observe, and as has long ago been shown to 

 be true) the anticyclone proper has characteristics of its 

 own w-hich distinguish it from these interspaces : its 

 movements are often slow, or it is stationary for a con- 

 siderable period, while in both hemispheres it has the 

 power of deflecting the course of the cyclones moving in 

 its vicinity more or less towards the right, except in par- 

 ticular positions. 



N ow let us look at the word " depression " and the 

 ideas associated with it. It would probably be an im- 

 possible as well as an undesirable task to get rid of this 

 term altogether, but for this reason it becomes all the 

 more necessary clearly to define its meaning. Originally 

 it signifies a lowering of the surface of the barometric 

 column due to a diminution of pressure on the surface of 

 the mercury in the cistern. It is equally well employed 

 to designate a "taking oft" or diminution of atmospheric 

 pressure. In any case, it might be employed to designate 

 such a diminution of pressure as takes place durmg the 

 lessening or the passing oft" of an anticyclone. But by 

 common usage it has come to be practically equivalent to 

 cyclone, the only difference being (i) that it naturally 

 refers to the diminution of pressure within the cyclo'ne, 

 and not the circulating winds, and (2) that it can be use- 

 fully applied to areas diverging considerably from the 

 circular form. The ease with which the idea of a saucer- 

 shaped hollow in the ocean of atmosphere is entertained, 

 and the associations of the word "gradient" (a word 

 valuable, suggestive, but figurative — a word for which 

 I can find no substitute, unless it be a coined one), have 

 certainly led to some misconceptions. Over the front or 

 ascensional part of a cyclone, atmospheric pressure is 

 greater at the level of four, five, or six miles above the 

 earth's surface than over surrounding regions at the same 

 level. It would be well for our storm-warnings if more 

 people were careful to observe the violent north-westerly 

 upper current prevailing immediately in front of, and 

 o\cr, the southerly winds which we feel when a cyclonic 

 disturbance is coming upon us from west-south-west. The 

 few who have noticed this cannot fail to be struck by the 

 fact that at the level of the cirrus the pressure must 

 increase with extreme rapidity at the same time that pres- 

 sure is decreasing at the earth's surface. It is true that 

 in the rear of the disturbance an e.xtension of the great 



