330 



knowledge: ♦ 



[Oct. 13, 1882. 



sncl eventually kept them on land in damp moss. She was 

 oblii.'pd to force them to eat by compelling earth-worms to 

 wrii5;le down their throats ; and fet-ding them well at the 

 critical stage of metamorphosis seems to have been tlie 

 miin condition of success. When the change from gills to 

 lungs was perfected, they fed tliemselves with avidity. 

 But Nature herself, notwitlistanding the ditliculties e.\- 

 perienced by Fraulein von Chauvin in transforming her 

 axolotls (some of which died under the treatment), appa- 

 ri'ntly succctnls sometimes in evolving amUi/nloma from tlio 

 Mexican newt ; therefore, assuming the variability of 

 spei-ilic microl)es under the influence of oxygen, there is 

 nothing unusual in the idea of the parasitic germs of 

 epidemics being spontaneously evolved from liarmless 

 saprophytes under peculiar conditions of culture, such as 

 the presence of various gases instead of free oxygen. In 

 that case, ill-ventilated sewers, stagnant pools, and other 

 places where aeration is not efficiently carried on, may con- 

 tinually evolve new crops of specilic disease germs. More- 

 over, no embryologist will object to the attribution of the 

 characteristics of species to the infinitely little, and the 

 resistance to retransfonnation under artificial conditions 

 displayed by M. Pasteur's typhoid microbe is only what we 

 might expect, on the assumption that it is a confirmed new 

 species. Fraulein von Chauvin's axolotls had to be forced 

 to eat under the new conditions which she provided for 

 them, and they would certainly have died if they had been 

 left to themselves. 



The behaviour of M. Pasteur's typhoid microbe, which 

 retained its specific or virulent character even under the 

 influence of oxygen, until it suddenly died, is singularly 

 like that of the a.xolotls. Does it not also explain the often 

 sudden disappearance of epidemics 1 The typhoid germs, 

 having acquired a parasitic or virulent habit, say in the 

 sewer, are conveyed to the bodies of human beings. Though 

 subsequently exposed even to the abundant oxygen of a 

 healthy locality, they resist its influence for a certain period, 

 spreading death meanwhile, and then, under the influence 

 of sanitary conditions, they suddenly become sterile and 

 Uie epidemic disappears. 



3KfblfVU£(. 



"TALKS ABOUT SCIENCE."* 

 ■fT^E have Vx-en anxious to .spr-ak very favourably of this 



> y t>ook, for reasons which will suggest themselves to our 

 readers ; but we cannot speak of it altogether so favourably 

 as we could wish. The duty we owe to our readers conflicts 

 with our wishes. It is but fair to mention, however, that 

 Mr Welsh, in the preface, says the volume has been pre- 

 pared " rath<T as a slight memento of one whose method 

 of teaching endeared him to a wide circle of students, than 

 as containing any original contributions to the general 

 knowledge of the subjects of which it treats." Many, 

 doulitlewt, will like to possess this little book as a memorial 

 of Mr. I)unman's life and laViOurs. Here, however, we are 

 concerned only to inquire how far thf- papers before us pre- 

 sent the true facts of science, and what are its r|ualitics as a 

 liteia-y production. Unfortunately it falls short in many 

 imf)ortant rr!sj>ects. We could pass over the facile way in 

 which space is wasted, though we have little liking for the 

 style of condescending badinage which has been introduced 

 by some South Kensington writers and lecturers, a sty U; which 



the author of this l>ook seems to have liorrowed rather than 



•Ta/U alroul Science. By the Isto Tilos. Ul.nhan, witfi ii 

 l>iogn|>hical nctice bj CnAKLU Welxii. (London : Grillitli ii 

 Farrm.; 



independently adopted. When Mr. Lookyer ti'lls us, for 

 instance, tliat rays, after passing into tlio spectroscope, "tie 

 themselves into a true lover's knot, before they come out 

 again " we do not feel that the image, however familiar, 

 is either explanatory or poetical. Nor are the phenomena 

 of solar atmospheric absorption explained by saying that 

 certain rays " are gobbled up on their way to the earth, and 

 come to us witli a balance on the wrong side of the account." 

 But apart from faults of stylo which Mr. Duiiman has 

 copied from his exemplars, there are many serious errors as 

 to matt<'rs of fact in the papers before us. Th(!ro is no 

 reason, for instance, if readers likt> tlmt style, that a writer 

 should not explain in a condescending nuinner why wo wear 

 dark clothes in winter ; but the explanation sliould be 

 correct In a single paragraph, the book before us tells us 

 that dark clothes conduct heat better than light ones ; that 

 they keep in the heat better than light ones ; that light 

 clothes radiate the heat instead of absorbing it : all which 

 stjitements are quite incorrect Mr. Dunman's explana- 

 nation of the way of finding the latitude at sea is open to 

 exception. " Supposing," he says, " a sailor wants to find 

 out his latitude — in other words, his distance from the 

 equator — this is what he does. Certain bright stars are 

 well known to him ; he knows exactly how far ofi 

 they are from the North or South pole, as the case 

 may be ; ho turns his telescope to a star which ho knows 

 to be 10° from the north or south, but ho finds out that 

 that star is 30° away from the point over his head — that is 

 to say, 30" away from liim ; thirty and ten aro forty, he 

 knows that lie is 40° from the North Pole. Now, the 

 distance from the Equator to the North Polo is 90°, and 

 forty from ninety, any boy in tho first standard will tell 

 you, leaves fifty ; and therefore the sailor knows that he 

 is in .")0° north latitude by such an ob.scrvation as the one 

 I have supposed. So, you see, the iinding your latitude is 

 simply noticing your distance from certain stars, tho posi- 

 tion of which is well known." Tho explanation is very 

 plainly worded, butunfortunately it is entirely (erroneous. 

 Such parts of it as aro, wo suppose, intended correctly, 

 are unmeaning. It is just such explanations as those which 

 send an audience away from a lecture with the fooling, 

 " Dear me, how easy it all is !" A fooling which changes 

 presently to tho thought that nothing has been nially 

 ex]>lained. After all, it is easy to (explain nothing (our 

 public men do that for us every day). It is also easy to 

 understand nothing. Naturally, in treating tho much more 

 difficult subject of the longitude more mistakes aro made. 

 Mr. Lockyer's mistake, which makes noon observations 

 at sea do duty for determining time, which of course they 

 aro quit(! unable to do, is repeated. Tho lunar method, 

 which Mr. Duntnan calls the lunar theory of finding the 

 longitude, is then tackled, which would have boon a daring 

 feat for Sir John Ilerschel. " I don't know of any one 

 having attempt<.'d to make that most abstruse Bubj(x-t clear 

 to a popular audience " Mr. Dunnian admits. This is how 

 the difficult task is achieved. " There is published in 

 Ijondon a wonderful almanac, called tho ' Nautical 

 Almanac,' which is published every year five years in 

 advance, and in that almanac there is laid down the exact 

 Greenwich time for every possildo position of tho moon 

 among tho stars. Conse(iuently, all that tho sailor has to 

 do is to find the exact jmsition of tho moon among the 

 stars, and to turn to his ' Nautical Almanac,' and having 

 found that position against it he will see marki^d the 

 (Jreenwich time." It would be well, indeed, for sailors 

 if the matter were as simple as it is hero described. 



There is much pleasant reading in this work ; but we 

 are afraid we cannot honestly say it is a trustworthy guide 

 on any subject of which it treats. 



I 



