176 



NA TURE 



[June 22, 1905 



The Romance of the Nitrogen Atom. 



With reference to the interesting letter by Dr. Irving 

 in N.VTURE of June 15 on " The Romance of the Nitrogen 

 Atom," I should like to point out that ammonia is not so 

 stable as is sometimes imagined. I have shown recently 

 not only that ammonia decomposes slowly at a temperature 

 of about 700° C, but that the decomposition is irreversible 

 {Proc. Roy. Soc, June), so that it will proceed until no 

 ammonia remains. The rate of decomposition decreases 

 rapidly with temperature, but it appears probable that even 

 at the ordinary temperature of the air the decomposition 

 must still proceed, although with excessive slowness. A 

 mi.\ture of nitrogen, hydrogen, and ammonia would thus 

 appear to be in " false equilibrium," in the same way as a 

 mi.xture of hydrogen, oxygen, and water vapour, but in 

 the opposite sense. The " silent discharge " will decom- 

 pose as \vell as synthesise ammonia, and brings about a 

 state of equilibrium. Sparking has also the same effect. 

 In these cases the equilibrium is a true one, so long as the 

 experimental conditions remain unaltered, and it ensues 

 when the rates of formation and decomposition of the 

 ammonia are equal. E. P. Perman. 



University College, Cardiff, June 17. 



Notes on the Habits of Testacella. 



Under the above heading in N.wure, vol. xxxiv. p. 617 

 (October 28, 1886), Prof. E. B. Poulton recorded the 

 capture of twenty-two specimens of this rare slug upon a 

 wall in Oxford. On that occasion there had been ex- 

 ceptionally heavy rains, and it was suggested that the 

 animals had been driven out of their usual habitat, the 

 earth, as it became sodden with moisture. I am in a 

 position to confirm the accuracy of this suggestion. Last 

 evening I captured five specimens of Testacella haliotidea 

 upon a stone wall near Charterhouse. The slugs were 

 apparently crawling out of the ivy which thickly clothes 

 the top of the wall, and were making their wav back to 

 the earth. During the previous eight days no less than 

 3^80 mches of rain fell at this place. It' seems probable 

 that the slugs had taken refuge in the dense shelter of 

 the ivy while the soil was unfit for them, and that on the 

 return of hot, dry weather were once again seeking their 

 subterranean quarters. Osw.^ld H. L.atter. 



Charterhouse, Godalming, June 15. 



Researches on Ovulation. 



I SHOULrf be greatly obliged if you would allow me to 

 state in your Journal that the paragraph on "ovulation" 

 ip relation to oestrus on p. 517 of my text-book on the 



vertebrata, which was issued in March last contains 



ul^l""! '° discoveries which were at that time un- 

 published, and that by inadvertence I omitted to direct 

 attention to this. The information was supplied to me by 

 Mr. Walter Heape The facts relating to rabbits were dis^ 

 covered by him, those relating to ferrets and dogs by Mr. 

 F. HA Marshall. These observations, with others have 

 recently been separately communicated to the Royal Society 

 for publication in the Proceedings. A. Sedgwick 



Trinity College, Cambridge, June 16. 



ABORIGINAL METHODS OF DETERMINING 

 THE SEASONS. 

 A N important and timely confirmation of the astro- 

 r „ ."0."i»cal significance attached to the stone circles 

 of Britain, and to the pyramids and temples of Ep-ypt 

 comes from the Far East. From an interesting paper 

 {Journal of the Asiatic Society. Straits Branch 

 January) by Dr. Charles Hose, who has made a special 

 study of the subject, we learn that the natives of 

 Borneo are at the present day using just the same 

 general principles in determining the advent of their 

 agricultural seasons as were used by the early Britons 

 and the ancient Egyptians between one and two 

 thousand years B.C. It will be remembered that, in 

 Greece, Mr. Penrose observed (see Nature, April 6) 

 that the Hecatompedon and the older Erechtheum, 



NO. l86o, vol. 72] 



built about 1495 b.c. and 2020 B.C. respectively, were 

 oriented to the cluster of the Pleiades at its heliacal 

 rising on May morning. In Egypt, Sir Norman 

 Lockyer found that the same asterism, as the deity 

 Nit-Isis, was probably employed as the warning star 

 for sunrise at the vernal equinox (" Dawn of 

 ."Astronomy, " 1894, p. 388). 



• .Although in Great Britain there are a great number 

 of stone circles, their astronomical significance has, 

 until quite recently, not been satisfactorily understood. 

 However, the recognition of Stonehenge as a solstitial 

 temple {Proc. Roy. Soc, vol. Ixix. pp. 137-147) led to 

 an inquiry into their possible character as observ- 

 atories, used by priest-astronomers to determine the 

 advent of the seed-time and other festivals, and the 

 investigation met with gratifying results at the out- 

 set. In the case of "The Hurlers," a group of three 

 stone circles situated near Liskeard, in Cornwall, 

 prima facie evidence was found that they were 

 arranged in their present positions, and the stones 

 around them placed in accordance, so that the 

 officiating priesthood could announce to the people 

 the arrival of the crucial seasons in the agricultural 

 year. .Among the stones used as azimuth marks at 

 " The Hurlers," there is one with an amplitude of 

 E. 11° N., which would mark the exact heliacal rising 

 of the Pleiades on May morning about the year 

 1600 B.C. {Proc. Roy. Soc, March 30). In addition to 

 the Pleiades, it has been found that the belt of Orion 

 was frequently used as the warning sign. 



Now we learn from Dr. Hose's researches that, at 

 the present time, the natives of Borneo, more 

 especially the Dyaks, are using the same stars in 

 much the same way to determine the season of the 

 year ordained by the local meteorological conditions 

 as the time for the preparation of the ground on 

 which they hope to grow their food supply for the 

 ensuing twelvemonth. During the semester October 

 to April the prevailing wind in Borneo is from the 

 north-east, and brings rain with it ; during the other 

 six months of the year the direction of the prevalent 

 wind is changed, but it brings none of the month-to- 

 month variations of conditions which — in lieu of more 

 refined knowledge — would lead the agriculturist of the 

 temperate zones to a more or less approximate know- 

 ledge of the season. 



In Egypt it was the advent of the Nile flood which 

 fixed the seed-time, and for which the celestial heralds 

 were observed ; in Britain it was, as it is now, the 

 advent of the warm, sunny weather that was the 

 matter of importance ; in Borneo it is the commence- 

 ment of the driest season that has to be recognised, 

 because the land which is to be cultivated is over- 

 grown by jungle or forest, and, before seed may be 

 sown thereon, a clearance must be effected. Like 

 the Malayans, the Dyak might use the moon as 

 his indicator, but then, like the Malayans, he would 

 probably get about eleven days wrong every 3'ear, 

 a serious matter where the dry season is of short 

 duration. The variation of the length of the day 

 is too small in the tropics to give a definite cue as 

 to the commencement of any special season. Con- 

 sequently, the Dyaks and many of the smaller neigh- 

 bouring tribes have recourse to the stars, and the 

 stars chosen as the heralds are the Pleiades (" bintang 

 banyak ") and Orion's belt (" bintang tiga "). The 

 native names are borrowed from the Malays, and this 

 probably indicates that the similar use of these stars 

 is not totally unknown among the latter. The 

 alternative expression used by the Dyaks in naming 

 the Pleiades is " Apai andau," meaning "the father 

 of the day," probably so called because it is the 

 heliacal rising of them that the natives watch for 

 before commencing their clearing process. In Borneo 

 it is, at present, merely an observation of the Pleiades 



