NA rURE 



\_Nov. 5, 1885 



OUR BOOK SHELF 

 Our Insect Enonics. By Theodore \\'ood. 220 pp. 



small Svo. (London : Society for Promoting Christian 



Knowledge, 18S5.) 

 Wf, have read the book through without discovering any- 

 thing (save in some questions that may be regarded as 

 essentially controversial) to find fault with. The illustra- 

 tions are not numerous, but to the point, and, although 

 somewhat coarse, are better selected than is sometimes 

 the case in books of this nature. There are fourteen 

 chapters in all, of which four are not inappropriately de- 

 voted to Aphides. The important subject indicated by 

 the title is treated calmly, and apparently with a view to 

 discourage the undoubtedly ill-effects produced by panic- 

 mongers in economic entomology. The first (or " intro- 

 ductory") chapter is well considered and well reasoned. 



Some Account of the " Palan Byoo" or " Teindoung 

 Bo," {Paraponyx oryzalis), a Lcpidoptcrotis Insect-pest 

 of the Rice-Phiiit in Burma. By J. Wood-Mason, 

 ■Officiating Superintendent, Calcutta Museum. (Cal- 

 cutta, 18S5.) 

 A PAMPHLET of 12 pp., with a plate, concerning a 

 lepidopterous larva that damages, but does not, as a 

 rule, appear to kill the rice-plant. It is more useful as a 

 contribution to pure biology than to economic ento- 

 mology. It describes one of the few Lepidopterous 

 larvK that breathe mainly by gills (or branchis), and 

 from this cause is considered an ally of our common- little 

 aquatic moth known as Paraponyx stratiotalis. The 

 vernacular names by which the insect is known are not 

 such as to be readily remembered by " foreigners ; " yet 

 it might have been better had the author not applied a 

 scientific name based solely on larva: and habits. All 

 babies are supposed to be very much alike, save to the 

 fond parents of each in particular. 



those of 1536 and 1537 nt Monte Nuovo, and in the late Ischiau 

 sliock.s. 



The thickness of ejected malerial.i is certainly gigantic, for the 

 maximum thickness of the Plinian eruption at Vesuvius was 

 under 10 nirtres, or just one-sixth that of Kratakab. 



There is reference made to round concretions called " Krakatab 

 marbles " that are met with amongst the ejectamenta, as being 

 things so far unobserved. Of course, it is not possible to judge 

 clearly from the description, hut I have little doubt that they 

 may be similar to those met with in the marl-like tufa of Ischia 

 and others, commonly found amongst the ejectamenta of Monte 

 Nnovo, which at the latter locality are fossiliferous. They are 

 simply concretions in a marine resorted tufa. 



The cooling of the atmosphere, referred to, at Batavia and 

 elsewhere at a moderate distance around the volcano, might be 

 explained by the vortex inrush of air towards the vapour column. 

 Observations of wind direction would be interesting as settling 

 this point. 



Another question of interest that was raised is the cause of 

 non-correspondence of one part of the earth with another in 

 seismic or volcanic activity. If we suppose a volcano to be 

 supplied with magma by ramifications from large extensions of 

 fluid rock within our globe, the gradual absorption of water by 

 one of these ramifications, and the consequent increase in its 

 tension may be quite independent of another ramification not 

 far off, yet perhaps more or less favourably placed in relation to 

 porous strata and superincumbent pressure and the necessary 

 results. 



I have drawn attention to these few points not with any 

 intention to undervalue the report, which has all the characters 

 of being one of the most important additions to the vulcano- 

 logical literature of the nineteenth century, but simply to prevent 

 certain unsound theories from becoming current. 



Naples, October 26 H. J. Johnston-Lavis 



The Recent Total Eclipse of the Sun 

 It may be interesting to your readers to supplement the 

 description given in Nature, vol. xxxii. p. 631, with the fol- 

 lowing notes which I have just received from a friend who 

 observed the eclipse at Nelson, N.Z. : " As the period of 

 totality passed away, a bright point of light as from a diamond 



LETTERS TO THE EDITOR 

 [ The Editor does not hold himself responsible for opinions ex^rt'sstd 

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 or to correspond 'd)ith the writers of, rejected manuscripts. 

 No notice is taken of anonymous comuiunications, 

 [The Editor urgently requests correspondents to keep their letters 

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Krakatao 



Although I have not yet had the good fortune of readint; 

 Dr. Verbeek's "Krakata~o," yet in the review published in 

 Nature of October 22 (p. 601) there are one or two points I 

 would like to draw attention to. In speaking of the earth- 

 quake of September, 1S80, we are told that it may have faciH- 

 tated the entrance of water by the Sunda fissure. If this were 

 so, it certainly seems a strange thing that no less than three- 

 years should be necessary to heat the water before the explosion 

 took place. I think that at present few geologists believe in 

 water gaining access to the magma by fissures while w-e neglect 

 percolation through porous rocks. It seems to me that the 

 above earthquake was the result of rupture and extension of the 

 magma-filled fissure towards the surface, in consequence of 

 which the final outburst was put off for a short time by increas- 

 ing the space for, and so lowering the tension of, the magma- 

 filled fissure. By a careful study of the products of many vol- 

 canoes I have .'■hown how the magma gradually dissolves or takes 

 up within it water from the surrounding rocks, and as this is a 

 slow process, the longer a volcano remains inactive, other things 

 being equal, the more violent will be the subsequent erujition 

 and the more vitreous will be the pumice owing to the rapid 

 cooling of the magma froth in consequence of the large absorp- 

 tion of heat in converting the dissolved water into the gaseous 

 state of steam, in the same way that the temperature of seltzer 

 water falls on allowing the gas to escape on removal of the cork. 

 The above earthquake has its parallels in a.d. 63 at Vesuvius, 



Total Eclipse of the Snii, ■. :.' , -.<-|itL-nilici- o, i ::35- 



of wonderful brilliance shot forth from the upper surface of the 

 moon, and at first this seemed to be only a flame, but it speedily 

 extended to the moon's shadow, passed downwards and to the 

 right, and totality was over." Another feature was the fall in 

 the temperature : " A thermometer which registered 50° at 



