THE ATMOSPHERIC PRESSURE OF NEW ZEALAND.

New Zealand Times, Volume XXXI, Issue 4893, 27 November 1876, Page 2

THE ATMOSPHERIC PRESSURE OF NEW ZEALAND.

The following is the paper “ On the Comparative Atmospheric Pressure of New Zealand and Great Britain ” (considered in reference to Dr. Newman’s theory of physiological deterioration), by Mr. Charles Rous Marten, E.R.G.S., E.M.S., M.Sc.M.S., read at the meeting of the Philosophical Society at the Colonial Museum, on Saturday evening, and alluded to in our condensed report in another column :

, 1. In a paper entitled “ Speculations on the Physiological Changes which obtain in the English Pace when transplanted to New Zea-land,’’.-read before this Society on the 30th September last, the author, Dr. Newman, in a very ingenious argument, endeavored' to show that in consequence of certain deficiencies in soil and climate of New Zealand, the English race may be expected to deteriorate, both physically and mentally, in future generations. Thus, if Dr. Newman’s theory be correct, children born in New Zealand of parents who have migrated hither from Great Britain should be inferior both physically and men-tally-taken on an average—to their progenitors, while their descendants in like manner, should deteriorate still further. Dr. Newman goes on to state that indications of this degeneration are even already visible. 2. The alleged deficiencies in the New Zealand soil and climate, to which this supposeddeterioration is attributed by Dr. Newman, consist mainly in an insufficient proportion of of phosphates as regards the soil and a diminution of atmospheric pressure in respect to the climate. The former of these two points it is not intended to discuss in this paper, the question being one rather for. a geological or chemical treatise. Moreover,, as Dr. Newman gives us reason to hope that the threatened degeneration from this cause may be averted by so simple and pleasant a prescription as an occasional whitebait dinner or an oyster supper, this aspect of the" case’ may be dismissed.

3. The other hypothetical cause of this hypothetical deterioration must be dealt with more seriously, inasmuch , as no course of diet or medical prescriptions would supply greater atmospheric pressure did any deficiency exist, as it could additional phosphorus if the. soil lacked the needful proportion of that element. It becomes therefore a matter of some moment as affecting the future of this polony, to ascertain whether the atmospheric pressure of New Zealand be really inferior to that of Great Britain as alleged. 4. First, let us understand clearly Dr. Newman’s arguments on this head. As I understand him, his contention stated in syllogistic form is as follows:

Major premiss-—Children bom in- countries where the atmospheric pressure is less-, have a tendency to be in inferior to those born where the atmospheric pressure is greater. Minor-premiss. —ln New Zealand the atmospheric pressure is less than in Great Britain; , Conclusion. — Ergo, children bom in New Zealand should be inferior to those born in England. 6. There is also an implied argument apriori, that inasmuch as this last condition has been observed to exist in certain cases, and as such an effect would be produced by the cause stated in the major premiss, ergo { such cause exists. : This last argument it is unnecessary to notice on the present occasion. 6. The object of this paper is, simply, to’ disprove the minor premiss of Dr. Newman's implied syllogism, and this I hope to be able to do, by showing on indisputable evidence that so far from the atmospheric pressure in New Zealand being less than that of Great Britain, it is in reality appreciably greater. 7. In support of his theory, Dr. Newman correctly states, on.,the authority of Captain Maury, Dr. - Buys-Ballot, and other undoubted authorities in meteorology, that the mean barometic pressure is generally lower in the Southern Hemisphere than in corresponding latitudes of the" Northern Hemisphere. This is a fact well known to meteorologists, and thoroughly recognised. At least, if not a “fact” strictly speaking, at any rate all the trustworthy observations, hitherto taken tend to prove this to be the case. Mr. Buchan, the secretary of the Scottish Meteorological Society, in his very able and valuable treatise on “The Mean Pressure of the Atmosphere over the Globe” (Transactions of the Royal Society of Edinburgh, . VoL XXV.), the standard work on this subject, gives the results of observations at 500 different places, situated in almost every part* of t]he globe. From these observations he has. . constructed a series ,of yearly, half-yearly, and monthly isobaric charts. In these charts the marked discrepancy between the barometric conditions of the two hemispheres is shown very clearly. In the Northern Hemisphere the isobars follow in most irregular and eccentric course, whereas in the Southern Hemisphere they flow almost in straight lines. It must be remembered, however, that owing to the greater area of ocean in the latter hemisphere, not only are there fewer, : local disturbing causes in the shape of spacious : continents .and lofty mountains, but also- the observatory sites are proportionately fewer. Hence the Southern isobars are in many cases merely arbitrary and approximate lines drawn from one point at which- continuous trustworthy observations have . been taken, to another similar point perhaps 5,000 or 10,000 miles away, as from the Cape of Good Hope to New Zealand, the intermediate points being furnished by casual intermittent observations made by passing vessels. It is possible that permanent observations, could - they be established in as many Situations as in ' the Northern Hemisphere, might necessitate con-, siderable alterations ,in the isobars, at present accepted. However, taking the existing isobars as a standard, we find that Whereas the isobar of 30in. follows a mean latitude of about 42deg. in the North Atlantic Ocean, the latitude of the same isobar in the South Pacific is only about 35deg. Similarly, the isobar of 29deg. j7oih.-fs found at a mean latitude of about 60deg. north, and only 4Sdeg. south. The very low pressure prevalent in the vicinity of Cape Horn is a. meteorological . feature well known to navigators. 8. All this of course "goes to. prove only that the mean pressure is less in the Southern than in- the Northern Hemisphere. Such in fact might have the form of Dr. Newman’s minor premiss, and so stated undoubtedly it would have been irrefragable, but in, that case, as the middle term of the syllogism would have been undistributed (it not being shown that the rule included New Zealand as compared with Great* Britain), the argument must have fallen to the ground. The real question is—not whether tbe pressure in New Zealand be less than in the corresponding northern latitude, but whether it be less than that of England, from whence, to use Dr. Neuman's words, the English race is transplanted.

9.. Dr. Hahn, o£ Vienna, in'his “Essay on the climate of New Zealand,” says: “It is a well-known fact that the pressure o£ air decreases very rapidly towards the pole in the Southern Hemisphere. We find this confirmed in New Zealand, where the medium pressure of air at the level of the sea, between 37deg. and 46deg. S. latitude, decreases from 29.981 inches to 29.804 inches ; whereas in the Northern Hemisphere in these latitudes the pressure of air remains between' 30*009 and 30*001 inches.”

10. Dr. Hahn is not quite accurate here. Reference to the isobaric chart will show that the isobar of 30' inches, which in the Southern Hemisphere lies entirely between lat. 32deg. in the South Atlantic Ocean, and 40deg. in the Indian - Ocean,* in the Northern Hemisspere varies most remarkably, descending tolat. 3Ode", in the North Pacific Ocean, rising to oodeg. in North America, descending again to 40deg. in the North Atlantic, then rising very gradually to lat. 65deg. in Asiatic Russia, next descending again suddenly to 30deg. at the starting point. 11. The point, however, is not material to the present argument, excepting so far as it goes to show the existence of such large barometric curves in the Northern Hemisphere where numerous observations havebeen taken, so that it would not have been an unreasonable hypothesis to suppose the existence of similar curves, if less extreme in degree, in the Southern Hemisphere, where observations are but few. Thus even had New. Zealand been in the same latitude in the south Great Britain inthenerth, and granting the diminished , pressure of the latter hemisphere, it would not have been at all impossible that this colony nevertheless might have enjoyed an atmospheric pressure as large as that of Great Britain.

12. Fortunately, however, authentic observation made in both countries are accessible, and being made under known conditions and with trustworthy and verified instruments are readily intercomparable. Those taken in New Zealand under the auspices of the meteorological department, and superintended by Hr. Hector,' comprise the barometric records of fourteen stations, distributed with tolerable evenness over the entire length and breadth of these islands, from Mongonui in the North (lat. 35deg. Imin.) to Southland (lat. 46deg. 17 min.), and from Napier in the East Gong. 176 deg. 55min) to Hokitika in the west (long.* 170 deg. 59min.), and extending over an average period of about ten years. 13. In order to institute a fair comparison between the two countries, I have selected the same number of stations (fourteen) in England, Scotland, and Ireland, so distributed as to embrace all parts of the kingdom. Thus in England I have taken Greenwich (London), Liverpool, York, Durham, Clifton, Worthing (Sussex), Stonyhurst (Lancashire), and Helston (Cornwall), at all of which places observations have been made and recorded by the Meteorological Society of England, from whose published returns I have compiled the averages shortly to be quoted. In Scotland I have taken Glasgow, Elgin, and Culloden, where observations are taken similarly for the Scottish Meteorological Society, and published in the journals of that body. The stations in Ireland are Dublin (observations made by Captain Wilkinson, R.E., at the Ordnance Survey Office), Belfast (observations taken at Queen's College), and Armagh (observations by Dr. T. R. Robinson at the observatory). All these observations, are like those in New Zealand, for a period of about ten years, and in both cases are reduced uniformly to a temperature of 32deg. Fab. and sea level. The results therefore are entirely comparable. 14. They are as follows : GREAT BRITAIN.

Difference in favor of New Zealand. o’o7. 15. Hence it is plain that the mean atmospheric pressure of New Zealand, instead of being lower than that of Great Britain, is 'O7 inch higher, and so disappears the clever but illusive theory built upon the contrary assump-, tion. In comparing the foregoing tables, it is curious to note that the barometric means at the respective English and New Zealand sta-, tions of lowest latitude are precisely identical, but the mean, although the highest in Great, Britain, is not so in New Zealand. The means of the three Scotch observatories, en revanche, are considerably lower than that of Southland, which is the min, New Zealand mean. Tt is alsonoticeable that whereas’the lowest latitude of any English observatory is 60deg. 7min., viz., Helston, in Cornwall, - the highest latitude of any New Zealand observatory—that of Southland, for 12 years under my personal charge, and I believe the most southern in the world—--is only 46deg. 17min. Thus the most polar, New Zealand observatory is only 3deg. -50 min. ■ nearer the Equator' than the: nearest English one, while the nearest New Zealand observatory is no less than ISdeg.’clpser. T 6. Dr. Newman’s ’major premiss I do not intend to discuss in the present paper, although the correctness of his assumption is open to considerable argument. 'This is the case more especially, inasmuch as it is based to a great extent on another assumption—that pressure increases or diminishes conversely with the degree of atnldspheric humidity. A long series of careful hygrometrical observations proves conclusively not only that the two atmospheric conditions are not necessarily correlative, but that often a marked barometric depression is associated with an equally marked atmospheric dryness; at all events, so far from the surface of the earth as observation can be carried, while a rapid barometic rise, and an influx of moist air also, are frequently coincident. The misapprehension obviously arose, from the general acceptance of the theory that the lower pressure of the Southern Hemisphere, as compared with the Northern, is due to the larger relative area of ocean in the former. But that the presence of aqueous vapor is not the only, or even the chief source of deficient pressure, can he proved beyond dispute. Comparison of barometic readings after the subtraction of the vapour tension will show this plainly. A very cogent illustration, however, is afforded by the tables already quoted, whichshow the pressure to be 29'932 at Hokitika, and only 29'871 at Christchurch, or -061 in favor of the West Coast, notwithstanding that the latter has a mean humidity of ‘B6, as compared with ’77.- at Christchurch, which, moreover, is to leeward of Hokitika as regards the prevailing wind. Hence the atmospheric pressure seems actually to diminish instead of increasing as the air loses its moisture. The truth appears to bo that the atmosphere is subject to disturbances more or less analogous to those of the ocean—waves, currents, eddies, and even tides, produced by causes and governed by laws as yet only imperfectly understood, but wholly irrespective of excess or deficiency of aqueous vapour, whose presence or absence probably is oftener the effect than the cause. 17. There are many other climatological characteristics of New Zealand related directly or indirectly to the subject of Dr, Newman’s able essay, and I-purpose treating of them on a future occasion. In the present paper I have simply endeavored to prove—and I trust I have succeeded in the attempt—that whether Dr. Newman’s speculations as to the probable

degeneration of the English race in New Zealand be well founded or not—for the sake of our adopted country we must hope the latter—at any rate, deficient atmospheric pressure does not enter as a factor into the problem. Dr. Newman said the purport of his argumsnt had been misunderstood. He had not asserted that diminished atmospheric pressure would cause degeneration, for he was aware that there were instances of the contrary. He certainly had believed ■ that the, atmospheric pressure of New, Zealand was less than that of England, that belief being founded on the statistics of recognised authorities, and hadstated that belief, as also his opinion that the English race would change in New Zealand, but the two subjects vvere not necessarily; related, and he had not intended so to represent them. Dr. Hector and Captain Edwin also spoke on the question, agreeing in the main with Mr. Rous Marten both as to the relative atmospheric pressure and as to the relation between the barometrical and hygrometrical conditions of the atmosphere. _ Mr. Rous Marten replied, pointing out that everyone who had heard or read Dr. Newman’s paper had put the same construction on his argument as he himself had done; indeed, his remarks that evening appeared to confirm the correctness of that construction, anditwasin consequence of the repeated attacks made on Dr. Newman. in the papers for the theory he was understood to have laid down, that led him to investigate the correctness of Dr. Newman’s data in the one particular dealt with in his paper. The discussion then concluded.

N. lat. Inches. Elgin .. 57° 38' 29790 Culloden 67 30 765 Glasgow 65 53 792 Durham 64 46 •810 Belfast.. 54 36 *882 Armagh 54 21 722 York ... 63 58 •872 Stonyirarst .. 53 61 •807 Liverpool 53 25 *889 Dublin. * 53 22 •886 Greenwich .. 51 28 ‘925 Clifton.. 51 28 •809 Worthing 50 49 •956 Heiston 50 7 ■977 Mean .. 29-848 NEW ZEALAND. S. at. Inches. Southland - .. 46* 17' 29803 Dunedin .. ' 45 52 •873 ; Qoeenstown .. 45 2 •987 Christchurch.. 43 32 Bealey.. 43 2 *805 42 41 . *932 Cape Campbell 41 50 •965 41 16 Wellington .. 41 16 *890 -Wanganui 39 56 30 070 Napier.. 39 29 29D17 Taranaki 39 3 Auckland 36 50 *930 Mongonul * 35 1 •977 Mean — 29918 .