276 



NATURE 



[January 17, 1901 



school. For example, one teacher of girls proposes to show by 

 furnace and acid that chalk gives off a definite quantity of gas. 

 This seems to me appropriate for an advanced university 

 student, but is not the thing for schools at all. 



Experiments to show the indestructibility of matter have this 

 advantage, that you must begin with some matter, and that you 

 must have some appliances on both of which the inquiring mind 

 may ieed. But as to where the matter goes to is another 

 matter, and as to what the measurements are all for, you might 

 as well be noting them during the progress of a pantomime. 



The same criticisms apply to physiology and botany. It is 

 said we cannot properly study the stomach without a preliminary 

 of histology. If so, they cannot be approached in schools, for 

 histology is a late science and is vain and empty to pupils. The 

 microbes of false ideas are thick in it. But Harvey knew no 

 microscopical histology, and yet he was not altogether a fool. 

 I find boys and girls of fifteen and sixteen studying the alter- 

 nation of generations in a phanerogam, and not only the nutrition 

 but the respiration of plants. Surely this is pushing on to 

 modern methods with a vengeance. But is there anything 

 gained in development of faculty ? Can they observe these 

 things, or do they trace a dim something which they are told are 

 there, and recognise them with the wild delight of an irrespon- 

 sible original researcher ? It is the delight of a child who has 

 jumped six feet high with just a little assistance. An indepen- 

 dent mind rejects all this and begs for a little exercise in kinds 

 of knowledge which you will find well represented in Pliny. 



When we turn back to the books of study which we read as 

 boys of fifteen and sixteen in the times when the ambition to 

 kick a goal or vault ten feet was so strong and so easily ousted 

 other ideas, how many very important laws we find which we 

 then read and now for the first time know. I can remember the 

 time when I tried to wake a class to the importance of Boyle 

 and Charles's laws, and I can also remember the time when I 

 remembered that my own old master vainly tried to wake us to 

 it. The result in neither case was thanks, and it was the 

 teachers who were wrong, not the pupils. We do our best, but 

 we are vastly wrong, and we inflict many injustices by force of 

 punishment just as in the old regime they broke the rulers over 

 our fathers' shoulders in teaching them practical prosody. A 

 little study of history will lessen this injustice. 



At the same time we must distinguish essential historic pro- 

 gress from mere accidents of time. I should be sorry to exclude 

 hydrogen explosions absolutely. James Sutherland. 



2, Stawell Street, Kew, Melbourne. 



Abbe's Optical Theorems. 



In the article, "Optical Science" (Nature, p. 203), as well 

 as in the preface to Prof. S. P. Thompson's translation of 

 Lummer there mentioned, regret is expressed at the neglect in 

 English text-books of Abbe's contributions to optical theory. 



Will you allow me to remark that statements and proofs of 

 Abbe's theorems will be found in §§ 2053-205/ of the 1899 

 edition of my " Deschanel, Part iv." They occur in the 

 chapter on "Systems of Lenses," and are based on careful 

 study of the writings of Abbe and Czapski. 



Ealing, January 9. J, D. Everett. 



Fireball in Sunshine. 



On Sunday, January 6 last, at oh. 52m. p.m., a brilliant 

 fireball was seen by many observers in Scotland. The sky was 

 clear and the sun shone brightly at the time. The meteor was 

 observed from Whiteinch Park and Great Western Road, 

 Glasgow, flashing across the north-western sky, and resembling 

 a rocket with a long streaming tail. One correspondent at 

 Glasgow says it travelled from the north-east to west, and that 

 in colour it was like reflected sunlight. Another writer describes 

 it as being of considerable size, " the fiery mass being as large 

 as a bowling ball with a glowing red tail attached." At 

 Killearn, N.B., the object passed from N.W, to W.N.W., and 

 was about 12 degrees above the horizon at the time of its 

 disappearance. It traversed a path of about 20 or 25 degrees, 

 during which it fell about 5 degrees. The radiant of the meteor 

 was probably in Auriga, Perseus, or Aries, so that it belonged 

 to a different system from that which furnished the brilliant 

 daylight fireball of January 9, 1900 (Nature, January 25, 

 1900). W. F. Denning. 



Bristol. 



Air and Disease. 



In these days of fresh-air treatment, some of your readers may 

 be interested in a quotation from Palladius " On Husbondrie," 

 an early fifteenth century MS. originally in Colchester Castle. 



"The longe-woo," says that writer, " cometh ofte of yvel 

 eire," i.e. lung-woe or consumption comes often of bad air. 

 The whole verse describes the eff"ects by which you may know 

 bad air or water, and is, perhaps, worth quoting in its entirety. 



" The longe-woo cometh ofte ofyvel eire, 

 The stomake eke of eire is overtake, 

 Take heede eke yf the dwellers in that leire 

 Her wombes, sydes, reynes swell or ake, 

 If langoure in thaire bledders ough' awake. 

 And if thoue see the people sounde and faire, 

 No doubt is in thy water nor thin aire." 



Thus we are told that both lungs and stomach are affected by 

 bad air and that, to detect bad air or water we are to see 

 whether the inhabitants have aches in stomachs, &c. 



The importance attached so early to air and water may, I 

 think, prove worth mentioning, as it is not what most of us 

 would expect. I came across the passage in turning over the 

 leaves of Lodge's edition of Palladius, published by the Early 

 English Text Society. Harold Picton. 



Clacton College, Clacton-on-Sea. 



NO. 1629, VOL. 63] 



RECENT ADVANCES IN THE GEOLOGY OF 

 IGNEOUS ROCKS. 



'X*HE closing years of the nineteenth century wit- 

 -»- nessed a revival of interest in the petrology of 

 igneous rocks, which must be regarded as marking an 

 important stage in the development of that subject. 

 Much detailed work, especially in the laboratories of 

 German universities, during the three or four decades 

 preceding had already accumulated a large body of 

 information ; but that work had been confined in great 

 measure to the strictly descriptive side of the science — 

 in short, to what is properly described as petrography — 

 and some of it fell rather into the domain of mineralogy 

 and physical optics than of geology. The value of such 

 a store of material cannot be overestimated ; but any 

 tendency which promises to shape it into a connected 

 system must be welcomed by geologists as the breath of 

 life animating the valley of dry bones. Such a move- 

 ment is undoubtedly felt at the present time, and may 

 perhaps be held to mark the transition in petrology from 

 the stage of observation to that of generalisation. An 

 igneous rock has come to be regarded, more constantly 

 than before, not merely as a mineral-aggregate, but as 

 the product of consolidation of a molten rock-magma ; 

 and consideration has been directed to the constitution 

 of such magmas and the conditions governing their 

 consolidation. Recognition of the importance of study- 

 ing the mode of occurrence of igneous rocks and their 

 relations to one another has led to a closer union of 

 observation in the field with research in the laboratory. 

 Much is being learnt concerning the geographical dis- 

 tribution of the rocks, their connection with crust-move- 

 ments, and the sequence of eruption of different types at 

 a given centre. The facts thus acquired, and especially 

 the fertile conception of " petrographical provinces," 

 each with its suite of igneous rocks having a community 

 of characters which bespeaks a common origin, have 

 confirmed the conviction that widely diverse rock-types 

 may be evolved from a common parent-magma. Hence 

 arises the problem, to which Brogger and others have 

 boldly addressed themselves, of the processes by which 

 such " differentiation " is effected and the conditions 

 which control them. Hence, too, another problem, a 

 corollary to the former, to frame a natural classification 

 of igneous rocks, based on genetic principles, to super- 

 sede the provisional classifications on various artificial or 

 Linnaean schemes which are at present current. The 

 questions involved obviously present great difficulties, 

 and petrologists would be the first to admit that some of 



