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SCIENTIFIC NEWS. 



[July 20, 1888. 



It has doubtless not escaped the observation of atten- 

 tive parents, that the growth of their children in height 

 appeared to be approximately in an inverse proportion 

 to their increase in weight. But the precise observations of 

 Malling-Hansen havenot merely established this point, but 

 have brought it into relation with the seasons of the year. 



But it is obvious that very much remains to be done in 

 this by-way of biology. Malling-Hansen's observations 

 were made upon children of both sexes between the ages 

 of nine and fifteen. It is now necessary to inquire whether 

 the same periods of increase in height and weight can 

 be traced from the fifteenth year to the attainment of full 

 maturity. Another point is the extension of the obser- 

 vations to children of other races and in other climates. 

 Malling-Hansen has already surmised a connection 

 between the intensity of growth of children — and of 

 course of all organisms — and the variations in the heat 

 radiated by the sun upon the earth. He does not suspect 

 that the fluctuations in the totality of heat derived from 

 the sun are the direct, immediate cause of the variations 

 in the increase of weight, but he, with Boys- Ballot, thinks 

 it probable that an unknown agent proceeds from the sun 

 in periods corresponding to the solar rotation of twenty- 

 seven days. This unknown agent he supposes to arrive 

 unconnected with meteorological conditions. Its sphere 

 of action, he thinks, includes all organisms which, 

 according to the time of the year, are differently sus- 

 ceptible to the stimulus of this '' growth-energy." 



In the meantime he points out in particular one among 

 the many practical conclusions to which his observations 

 may lead. As much as possible of the two periods of 

 maximum growth — i e., in height and weight — should be 

 passed in the summer holidays. In this respect the 

 Swedes and the South Germans have, by instinct or 

 accident, outstripped the North Germans and the Danes. 

 The former give their children two entire months of 

 holiday in the summer ; in some parts even more. Some 

 schools in the west of Germany, we must remark, give 

 no holidays at all. 



The summer holidays should begin at the end of June 

 and extend to the beginning of September, thus allowing 

 full play for the maximum periods 01 growth. 



Besides the above-mentioned three annual phases, 

 Malling-Hansen has recognised periods 01 25 and of 75 

 days within which the conditions of growth undergo 

 cyclical variations. 



As regards the daily fluctuations, he finds that on the 

 average of the three months, December 1883, and Janu- 

 ary and February 1884, every boy in the institution lost 

 about |oz. in weight between the conclusion of dinner, 

 at two p.m. to nine p.m., and in the course of the night, 

 from nine p.m. to six a.m., "a further amount of about 

 2ozs. From six a.m. to one p.m., just before dinner, 

 each boy regained nearly |oz. Whilst the dinner effected 

 in each an average increase of 2I0Z. 



The following changes of height were observed in 22 

 boys, varying from 13 to 16 years, during five weeks. 

 From 6 to 8 a.m. there was a loss of 4 millimetres ; 

 during lessons, 8 to 9 a.m., a gain of 3 millimetres ; 

 from 9 to 10 a loss of 1 millimetre. From 10 to 11 

 (play-time), a further loss of 1 millimetre. Between 1 1 

 and 12 a.m. (lessons), again of 2 millimetres; from 12 

 to 1 p.m., a loss of 4 millimetres ; and from 1 to 5 p.m., 

 of 3 millimetres. Thus from 6 a.m. to 5 p.m. there was a 

 nett loss of 9 millimetres in height (nearly two-thirds of an 

 inch). From 5 to 9 p.m. the changes were trifling, and 

 from 9 p.m. to 6 a.m. there was a gain of 9 millimetres. 



CORRESPONDENCE. 



The Editor does not hold himself responsible for opinions expressed 

 by his correspondents, nor can he take notice of anonymous com- 

 munications. All letters must be accompanied by the name and 

 address of the writer, not necessarily for publication, but as v 

 guarantee of good faith. 



A CIRCLE PROBLEM. 



Your correspondent, "A P. T.," has again omitted to show 

 the principle upon which his facts are based. The circum- 

 ference of a circle = diameter xir (7r = 3 - i4i6), and if, there- 

 fore, we have two circles, A and B — A with diameter 8 ft. and 

 B with diameter 12 ft. — then the difference of the circum- 

 ferences of A and B = {(i2X7r)-(8x?r)} ft. = (4X7r) ft. If A 

 and B had diameters of 10 and 15 ft., the difference of the 

 circumferences would be {(15 xt) -(iox 7r)|ft. =5 X7r ft- Thus 

 we see that the difference of the circumferences of two circles 

 is always the difference of the diameters x ir ; and hence, 

 when the difference of the diameters is always the same, the 

 difference of the circumferences is always the same, no 

 matter how small or how great the circles may be. This, as 

 might be expected, is not the case with the difference of the 

 areas of the circles, that difference being proportional to the 

 difference of the squares of the diameters or radii. 



Your correspondent also, in quoting from " Whitaker's 

 Almanack," has given us the diameter of Venus instead of the 

 diameter of the Earth, which is 7,926 miles (" Whitaker's 

 Almanack," 1888, page 78). One error, however, is a great 

 improvement on four, and seems to show that " A. P. T.'s " 

 type-writer is not quite as incorrigible as he would have us 

 believe. Kuklos. 



COSMICAL ORIGIN OF HAILSTONES. 

 Ordinary meteors fall on our earth in their own time and 

 without waiting for any special terrestiial weather. Hail- 

 stones, on the other hand, choose suitable conditions and 

 appropriate weather. If Schwedoffs theory (mentioned by 

 Mr. Williams in " Table Talk," No. 26 and following pages, be 

 correct, we ought to hear of an occasional hailstone or shower 

 of hailstones at times when terrestrial conditions are dia- 

 metrically opposed to their production. Is there record of 

 any such occurrence ? If not, this seems to show a weak 

 point in the theory. F. M. 



THE COLDNESS OF JULY 11 AND 12. 



As a rule, the hottest day in the year in London is July 16th. 

 We are therefore within a week of that date, and yet for two 

 days I have been luxuriating in the warmth of an ever-ready 

 gas fire. 



It would not be at all difficult to find two days in January 



warmer than these two in July; but as it would be rather 



confusing to compare with two, I take only one — the first 



that comes to hand : — 



Minimum. 

 Deg. 



1877 — January 1st . . . . 493 



1888— July nth .. .. 42'8 



1888— July 1 2th .. .. 45 "4 



These two days have therefore been colder than the 1st of 

 January — July nth by 5'i deg. and July 12th by 3-2 deg. 

 Memory is not a safe guide, but I remember no parallel in 



July. 



Some years back Mr. Glaisher, F.R.S., worked up the daily 

 temperature at Greenwich from 1814 to 1873, and in that long 

 period I can trace no days in July at all comparable with 

 these, except two, one in 1836 and one in 1856. The precise 

 figures are as follows : — 



Mean Temperature at Greenwich. 

 Deg. 



1836— July 20 . . 477 

 1856— July 8 . . 48-0 

 Wednesday, July nth, is therefore absolutely without pre- 

 cedent, and to-day is very nearly so. 



G. J. Symons, F.R.S. 

 62, Camden Square, N.W., July 12. 



9 a.m. 



Maximum. 



Deg. 



Deg. 



50-0 



54-0 



45-4 



557 



49'9 



54-2 



Mean Temperature at Camden Sq. 

 Deg. 

 1888— July II .. 46-2 

 1888— July 12 . . 48-1 



