Sept. 7, 1882] 



NA TURE 



455 



7. When there is a pause in the respiratory phrases it 

 always occurs in inspiration. 



8. In all insects vigorous enough to furnish suitable 

 curves (such as the large Coleoptcra) one finds that the 

 inspiration is usually slower than the expiration, and that 

 the latter is often sudden (confirming an observation by 

 Sorg in 1805). 



9. In most insects expiration is alone active, inspiration 

 being passive, and due to elasticity of the teguments and 

 the tracheal walls. (This confirms previous observa- 

 tions.) 



10. Nearly all insects possess only expiratory muscles. 

 M. Plateau has found muscles aiding inspiration not only 

 in Hymenoptera and Acridians (Rathke, Graber), but in 

 Phryganeidie. 



11. The superior and inferior diaphragms of Hymen- 

 optera have not the role Wolff attributes to them (a con- 

 firmation of objections by Graber). 



12. Many insects, perhaps all, perform, with their 

 abdomen, general movements, sometimes small, some- 

 times very ample, which do not coincide with respiratory 

 movements, properly so called, and must be distinguished 

 from them. 



13. The respiratory movements of insects are purely 

 reflex, persisting in the decapitated animal, and even in the 

 isolated abdomen in forms whose nervous system is not 

 condensed. In the latter case these movements are 

 excited or retarded by the same causes which excite or 

 retard them in the intact insect (a confirmation of previous 

 observations). 



14. The metathoracic ganglions are not, as Faivre sup- 

 posed, special respiratory centres (a confirmation of the 

 views of Barlow and Baudelot on Libellute). 



15. The abolition of respiratory movements by destruc- 

 tion of the metathoracic ganglions in Dytiscidae and 

 other Coleoptera, results from the condensed state of 

 their nervous system, in which a certain number of 

 abdominal ganglions are fused with those of the meta- 

 thorax. 



16. In insects with a condensed nervous system the 

 excitation or partial destruction of a complex nervous 

 mass resulting from the union of successive ganglionary 

 centres always affects all the centres entering into the 

 constitution of this mass. 



DIARY OF VESUVIUS, JANUARY 1 TO 

 JULY 16, 1882 



T N the account given in Nature, vol. xxv. p. 294, the 

 *■ eruption that has been going on in December was 

 described up to the last day of 188 1. As the height of 

 the lava column had been diminished by the lateral out- 

 lets, the surface was consequently some considerable 

 distance below the lip of the crater, its level on ordinary 

 occasions being only a few metres below. 



Under ordinary conditions the ejectamenta consist of 

 masses of fluid lava blown out as the spray from an 

 effervescing liquid. They form the so-called lava cakes, 

 being flattened out by their fall, while still plastic. They 

 are usually very spongy, or scoriaceous, and rapidly 

 disintegrate. In the present instance, however, as the 

 vapours quitted the lava at some considerable depth, 

 these plastic masses could not reach the surface. This 

 rapid escape of vapour through the narrow tube between 

 the lava surface and the crater lip, was under analogous 

 conditions to the powder gas in a fire-arm. If, for 

 instance, we imagine a cannon, whose bore is composed 

 of materials easily broken up, we have a rough illustration 

 of what takes place. The lava-cakes were replaced by 

 ejectamenta derived from the components of the sides of 

 the chimney, such as compact lava fragments, lapilli, old 

 scoria cakes, all more or less altered and decomposed by 

 the hot acid vapours, to which they had been exposed 

 for considerable periods. 



Such a condition of things naturally results in the 

 straight-tube or chimney assuming the form of a funnel, 

 or conical hollow whose apex will be at or near the lava 

 level, that is to say, at the point where the gaseous 

 products quit the fluid magma. We have, in fact, two 

 conditions upon which the size and depth of a crater 

 depend, namely, height of lava column, and amount and 

 force of vapour escaping. Naturally the effect would be 

 modified by local causes, and also the difference of com- 





Sketch after Nature on July 16, l88», 9.30 a.m. View from the nnrth of the 

 ones an! craters of December, 1881, and January to July 16, 1882. 

 The outer rim is br. ken away over the old fissure to the left or east. 

 The smaller bocca is beneath the little figure, there is probably the 

 remnants of another beneath the middle, or left figure. 



ponent materials. The ejectamenta which in this manner 

 were very different from that of ordinary occasions, were 

 deposited simultaneously in a rim-like manner around 

 the new crater. 



Thus we see how a nearly perfect cone of eruption, 

 such as existed in the beginning of December, composed 

 as it was of alternate beds of lava and scoria cakes, with 

 a chimney, but without a crater, may be converted into a 

 low truncated cone, whose base is of an area considerably 

 larger than that of the original, but whose height is much 



1, Outline profile of apex of 



December 31. t88t : 3. outline section on April 33, 1882 i.e. the con- 

 tinuous line) ; 4. cone and crater formed between April 23 and July 16, 

 1882; a. materials, lava, and scoriae since 1872 ; B, ditto, since December 

 31. »88t ; c. ditto, since April 23. 1882. 



less. The interior now occupied by a crater proportion- 

 ally large. The whole of these changes occurring with- 

 out the addition or abstraction of any materials, except 

 an ash blown away by the wind. 



On January I, Vesuvius had become quiet, and the 

 feeble ejections consequent thereon could no longer hoist 

 the materials over the new crater edge, but were instead 

 building up a new cone of eruption around the vent at the 

 bottom of the craterial hollow. 



