Jan. 15, 1880] 



NATURE 



?49 



in quoting my name from a former volume of Nature in 1S72, 

 as laving then announced a cold w ave of climate temperature 

 being due to commence in iSyS'S ; or, as he is kind enough to 

 say, the very day on which the severe winter of the years 1878 

 and 1879 did begin. 



I must decline, at all events, the full honour, for these two 

 reasons : firstly, the quoted datum was intended by me to signify 

 the middle, not the beginning, of that cold wave ; and as that 

 lasted thirteen months, my date was between six and seven 

 months too soon. Secondly, when I published again on the 

 subject in the Edinburgh Astr. Oiservations of 1877, I indi- 

 cated not 1878-8, but 1877-8 as the probable date of the then 

 coming, now past, wave of cold, or erred much more than in 

 1872. 



I have recently been looking into the reason of that latter 

 calamitous failure, and find it clearly enough now on the plates 

 uf projections in that volume in this fact— that the then expected 

 minimum of solar spots was inserted for 1877-5, ° r "early two 

 years sooner than sun observations have since then shown it to 

 be. Kectifying, therefore, now that Quantity, and in the then 

 absence of our rock thermometers (which had first indicated the 

 remarkable cycles of temperature in striking connection with the 

 whole period, though not the details, of the sun-spots) using 

 merely air-temperatures and re-drawing the curves, the middle 

 epoch of the late cold wave comes out iSyg'i, and of the next 

 hot wave iSSo'S. 



Now these hot waves, I have always maintained, are more 

 important, more regular, and more directly of solar origin, than 

 the cold waves which are rather due to some indirect earthly 

 effects of watery vapour and its transformations. It may be 

 worth while, therefore, when we are now, as I believe, on the 

 threshold of one of the heat-waves, to mention shortly the data 

 on which the expectation is founded. 



These are mainly the actual observations of no less than five 

 occasions of such maxima of temperature occurring in a peculiar 

 kind of dependence on successive sun-spot minima ; or rather 

 on the beginning, in each case, of the forces of a new spot cycle. 

 The last such heat-wave was in lS68 - 8, or I '8 year after the 

 then last sun-spot minimum. Next before that in 1857-9, or 1*9 

 years after its previous sun-spot minimum. Before that, in 1846-4, 

 or 2-4 years after the same solar test. Before that again, but 

 then depending only on old atmospheric temperature observa- 

 tions, asourrock thermometers were not then existent, in 18345, 

 or 1 year after ; and still further back, in 1826-5, or a ' s0 about 

 1 year after the then last sun-spot minimum. 



These intervals from one to the other of the hot waves are by 

 no means arithmetically equal, being I0'9, 1 1 -5, 1 1 '9, and 8'0. 

 This last (really the earliest of the series) is a frightful inequality, 

 but is borne out, first, by the sun-spot period of that cycle as 

 given by M. Schwabe, having been also anomalously short ; and 

 second, by this remarkable testimony, which I have only just 

 become acquainted with, in a pamphlet of most independent 

 character by Sir Robert Christison, Bart., M.D., on tree-growth, 

 read before the Botanical Society in Edinburgh : — 



"The wonderful season of 1S26, when warmth and sunshine, 

 commencing with March, ended only with September, and when 

 the summer was continuously such as to change in some respects 

 the habits of the people." 



Tlic year 1826 was therefore a crucial case, not only for a 

 maximum of temperature and sunshine in Scotland, but for its 

 keeping such remarkable pace with the then anomalously 

 shortened period of sun-spots. While the presently coming 

 case of 1880 will equally prove, by what I have detailed above, 

 that no certain success in weather predictions for several years 

 beforehand can be hoped for, unless the dates of sun-spot 

 minima can be also announced by authority beforehand to a very 

 much smaller quantity than two years of error ; and that no 

 mean duration of the sun-spot cycle comes close enough to the 

 fact of the large variations between one cycle and another. We 

 must have therefore each cycle of sun-spots fixed by its own 

 dates alone, and not smoothed away and improved out of crea- 

 tion by being made apparently conformable to others. 



1 have not yet seen, by those able men who believe they have 

 traced sun-spots to planetary influences of position on the sun, 

 any attempt, from the planetary places in almanacs, to compute 

 the dates of all the solar minima of spots, say from 1825 to 

 1900. But something of that kind appears now to be necessary 

 for the next steps of the science of the future. 



Fiazzi Smyth 

 15, Royal Terrace, Edinburgh, January 9 



Cranial Measurements 



In the notice of my catalogue of crania which you have been 

 good enough to insert in Nature, vol. xxi. p. 222, your reviewer 

 has given me credit for originality of method, to which I have no 

 wish to lay claim. 



1. In reference to the mode of taking the horizontal circum- 

 ference, it is said that I pass "the tape line, not over the 

 prominence of the glabella, as is customary with crani. logists, 

 but abo/eit, around the supra-orbital line." The fact i , that 

 the method which I have adopted, so far from being a deviation 

 from what is customary, is that recommended 

 "Instructions Craniologiques," drawn up by Broca and pub- 

 lished by the French Anthropological Society, and which is used, 

 certainly by the large majority, if not by all the craniologists 

 with whose writings I am acquainted. 



2. With regard to the more important measurement of the 

 antero-posterior diameter of the cranium, more important on 

 account of its influence on some of the most characteristic 

 indices, there are, unfortunately, still considerable differences of 

 method, and it was only after very full consideration of the 

 subject that I decided not to follow the French instructions, but 

 to adopt the plan used by Rolleston in " British Barrows," by 

 Barnard Davis in his " Thesaurus Craniorurn," and by the majo- 

 rity of German anthropologists. So fully was I c nvtnced of the 

 expediency of the latter, that after having already mi a u red the 

 whole of the crania in the collection, and calculated the indices 

 by the method which included the prominence of the glabella 

 in the cranial length, I took the trouble to remeasure them, with 

 the results given in the catalogue. The object beinu to obtain, 

 as near as may be, an idea of the form of the brain case, it 

 appears desirable to exclude all extraneous projections which 

 have no relation to this form. The impossibility of eliminating 

 every sonrce of fallacy, such as those occasioned by the varying 

 thickness of bone or of diploe, is no argument against 

 endeavouring to reduce them, as far as we can, to a mini- 

 mum. The projection caused by the development of the 

 frontal sinuses should certainly not be omiited in a com- 

 plete description of a skull, but it no more affects the 

 form of the cranium proper, than the prominence of the nasal 

 1-ones or of the maxilla, which, important and instructive 

 as they are from other points of view, are usually ignored in 

 giving what is called the maximum length of the skull, although 

 if the term is to be taken in its literal sense, they have a~ much 

 claim to be included as the glabella or supra-orbital r 



Many other arguments might be adduced and authorities given 

 for the usage I have adopted, but I will bear 111 mind your 

 request for brevity. W. 11. FLOWER 



Royal College of Surgeons, January 1 1 



"Why the Air at the Equator is not Hotter in January 

 than in July "—Freezing of the Neva 



In Nature, vol. xxi. p. 120, Mr. Croll gii 

 why the equator is not much warmer in January than in July, 

 notwithstanding the greater nearness of the sun at the former 

 'eason. To state the case briefly, he, having recalled the fact 

 that the whole earth is colder i:i January than in July, because 

 in the former the cold winter of the northern (or principally 

 land) hemisphere coincides with the mild winter of the 

 (or principally water) hemisphere, he continues : " Con equently 

 the air which the equatorial regions receive from the trades must 

 have a higher temperature in July than in January. 'I he northern 

 is the dominant hemisphere; it pours in hot air in July and cold 

 air in January, and this effect is not counterbalanci d by the air 

 from the opposite hemisphere. The mean temperature of the air 

 bassing into the equatorial regions ought therefore to be much 

 nipherm July than in January, and this it no doubt would be 

 we're it not for the counteracting effects of eccentricity. And 

 farther • "There is another cast which must also tend to lower 

 the January and raise the July temperature of the equator : the 

 northern trades pass farther south, and consequently cool the 

 equatorial regions more during the former than the latter season. 



I maintain that there is no such influence of the n rfnerp 

 trades on the temperature of the equator, because they scarcely 

 anywhere reach it, and then because the lower latitudes of Me 

 northern hemisphere are not colder in January than those of the 

 southern hemisphere in July. In the Atlantic the northern tradv 

 do not reach the equator at all in January, but only in 1'ebruary , 

 March, and April, and this but in the western part of the ocean. 



