648 



NA TURE 



[Oct. 30, ii 



practically ubiquitous appearance in a germinating and ailult 

 condition. The presence of putrefiable or putrescent matter 

 determines at once the germination of the always-present spore. 

 Bnt a new question arises. These spores are definite products. 

 In the face of some experimental facts one was tempted to 

 inquire, have these spores any capacity to resist heat greater than 

 the adults ? It was not easy to determine this question. But 

 we at length were enabled to isolate the germs of seven separate 

 forms, and by means of delicate apparatus, and some twelve 

 months of research, to place each spore sac in an apparatus so 

 constructed that it could be raised to successive temperatures, 

 and without any change of conditions examined on the stage of 

 the microscope. 



In this way we reached successive temperatures higher and 

 higher until the death point — the point beyond which no sub- 

 sequent germination ever occurred — was reached in regard to«i 

 organism. The result was striking. The normal death point 1 

 for the adult was 140 F. One of the monads emitted from 

 its sac minute mobile specks — evidently living bodies — which 

 rapidly grew. These we always destroyed at a temperature of 

 l8o J F. Three of the sacs emitted spores that germinated at 

 every temperature under 250^ 1 . Two more only had their 

 power of germination destroyed at 260"' F. And one, the least 

 of all the monad forms, in a heat partially fluid and partially dry, 

 at all points up to 300" F. But if wholly in fluid it was destroyed 

 at the point of 200" F, 'I he average being that the power 

 of heat resistance in the spore was to that of the adult as II 

 to 6. From this it is clear that we dare not infer spontaneous 

 generation after heat until we know the life-history of the 

 organism. 



In proof of this I close with a practical case. A trenchant and 

 resolute advocate of the origin of living forms de novo, has 

 published what he considers a crucial illustration in suppotl of 

 his case. He took a strong infusion of common cress, placed 11 in 

 a flask, boiled it, and, whilsl boiling, hermetically sealed it. lie 

 then healed it up in a digest! 1 to 270' I'. It was kept for nine 

 weeks and then opened, and, in his own language, on microscopical 

 examination of the earliest drop "there appeared more than a 

 dozen very active monads." He has fortunately measured and 

 roughly drawn these. A facsimile of his drawing is here. 

 He says that they were possessed of a rapidly m iving lash, and 

 that there were other forms without tails, which he assumed 

 were developmental stages of the form. This is nothing less 

 than the monad whose life-history I gave you last. My 

 drawings, magnified 2500 diams,, of the active organism and the 

 developing sac, are here. 



Now this experimenter says that he took these monads and 

 heated them to a temperature of about 140" I 1 "., and they were 

 all absolutely killed. This is accurately our experience. But he 

 says these monads arose in a closed llask, the fluid of which 

 had been heated up to 270 F. Therefore, since they are killed 

 at 140" F., and arose in a fluid after being heated to 270° 1 \, they 

 must have arisen denovo! But the truth is that this is the monad 

 whose in onl) loses its power to germinate at a temperature 

 (in fluid) of 20 1°, that is to say, 20 F. higher lien the heat to 

 which, in this experiment, they had been subjected. And 

 therefore the facts compel the deduction that these monads in 

 the cress arose, not by a change of dead matter into living, but 

 that they germinated naturally from the parental spore which the 

 heat employed had been incompetent to injure. Then we con- 

 clude with a definite issue, viz., by experiment it is established 

 that living forms do not now arise in dead matter. And by study 

 of the forms themselves it is proved that, like all the more com- 

 plex forms above them, they arise in parental products. The law 

 is as ever, only that which is living can give origin to that which 

 lives. 



WHIRLWINDS AND WATERSPOUTS l 



\X7HIRLWINDS, whether on sea or on land, have their 

 characters in great part alike. For simplicity it will be 

 convenient to begin by taking up only the case of whirlwinds on 

 sea, as thus the necessity for alternative expressions to suit both 

 eases, that of sea and that of land, will be avoided. 



It may be accepted as a fact sufficiently established, both 

 by dynamic theory and by barometric observations, that at 

 the sea-level the pressure of the air is less in the neighbourhood 



1 Paper by James Thomson, LL.D., n.Sc., Professor of Civil Engineering 

 a- J Mechanics in tin: I tniversity of I tlasgow, read in Section A, at the British 

 A sscciation meeting at Montreal, on Monday, September r. 



of the axis of whirl than it is at places farther out from the axis, 

 though within the region of the whirl. The apocentric force 

 (centrifugal force) of the rapidly-revolving air resists the inward 

 pulsive tendency of the greater outer than inner pressure. But 

 close over the surface of the sea there exists necessarily a lamina 

 of air greatly deadened as to the whirling motion by fluid fric- 

 tion, or resistance, against the surface of the sea ; and all the 

 more so because of that surface being ruffled into waves and 

 often broken up into spray. This frictionally-deadened lamina 

 1 ail-, because of its diminished whirl speed, less apocentric 

 force than the quicker-revolving air above it, and so is incapable 

 of resisting the inward pulsive tendency of the greater outer than 

 inner pressure already mentioned. Hence, while rushing round 

 in its whirl, the air of that lamina must also be flowing in centre- 

 ward. 



The influx of air so arriving at the central region cannot 

 remain there continually accumulating ; it is not annihilated, 

 and it certainly does not escape downwards through the sea. 

 I here is no outlet for it except upwards, and as a risi g central 

 core it departs from that place. This is one way of thinking 

 out some of the conditions of the complex set of actions under 

 contemplation ; but there is much more yet to lie considered. 



Hitherto, in the present paper, nothing has been said as to 

 the cause or mode of origin of the diminished barometric 

 pressure which, during the existence of the whirlwind, does 

 actually exist in the central region. Often in writings on this 

 subject the notion has been set forth that the diminished pres- 

 sure is caused by the rapid gyratory motion of the whirling air ; 

 bui, were we to accept that view, we would have still to ask, 

 How does the remarkably rapid whirling motion receive its own 

 origin? The reply must be that the view si, offered is erro- 

 neous ; and that, in general, a diminished pressure existing at 

 «ie particular region is the cause rather than the effect of the 

 rapid whirling motion ; though in some respects indeed these 

 two conditions can be regarded as being mutually causes and 

 . each being essential to the maintenance of the other, 

 while there are also some further promoting causes or condition, 

 not as yet here mentioned. 



Il seems indubitably to be the truth that ordinarily for the 

 genesis of a whirlwind the two chief promoting conditions are : 

 firstly, a region of diminished barometric pressure, this dimi- 

 nution of pressure being, it may be presumed, due to rarefac- 

 tion of the atmosphere over that region by heal, and sometimes, 

 further, by its condition as to included watery vapour; and, 

 secondly, a previously existing revolutional motion, or differen- 

 tial horizontal motion, of the surrounding air, such revolutional 

 mi differential motion being not necessarily of high velocity ;at 

 any part. 



The supposed accumulation of air rarefied by heal or other- 

 wise, for producing the abatement of pressure may, the author 

 supposes, in some cases extend upwards throughout the whole 

 depth of the atmosphere ; and in some cases may be in the 

 form of a lower warm lamina which somehow may have been 

 overflowed or covered by colder air above, through which, or 

 into which, it will tend to ascend : or the lower lamina may in 

 In- warmed in any of several ways, and so may get 

 a 1- n Ian y to rise up through the colder superincumbent atmo- 

 sphere, t Hi this part of the subject the author believes there is 

 much scope for further researches and advancements both ob- 

 servational and considerational ; — that is to say, by encourage- 

 ment of a spirit towards accurate observation ; ami by collection 

 and scrutiny of observed facts and appearances ; and by careful 

 theoretical consideration founded on observational results or 



suppositions. 



I the author it seems probable that the great cyclones may 

 have their legion of rarefied air extending up quite to the top of 

 the atmosphi re ; while often whirlwinds of smaller kinds, many 

 of the little dust whirlwinds, for instance, which are frequently 

 I-. be teen, may terminate, or gradually die out, at top in a 

 layer or bed of the atmosphere different in its conditions, both 

 as to temperature and as to original motion, from the lower 

 layer in which the whirlwind has been generated. In many 

 such cases the upper air may probably be cooler than the lower 

 air in which the whirlwind originates. 



( >n the subject of the actions going on at the upper parts or upper 

 ends of whirlwind cores in most cases, the author feels that he is 

 able to offer at present little more than suggestions and speculative 

 conjectures. In very many descriptions of the appearances pre- 

 sented by those whirlwinds with visible revolving cores, which 

 are called waterspouts, it is told that the first appearance of the 



