November 1, 1890.] 



KNOWLEDGE. 



253 



may i3ometimes be found in swarms behind panels and 

 wainscoting in badly infected houses, the trachea? can still 

 be recognised as perfect tubes after all the rest of the soft 

 parts have dried vip and disappeared. All that it is neces- 

 sary to do with the dried carcase is to soak it in water till 

 it becomes sufficiently flexible to be manipulated without 

 breaking. On cutting through the skin, the tracheal 

 tubes will be found spreading about in various directions, 

 and may be examined where they lie, or removed and 

 placed between glass, when a high power may be brought 

 to bear upon them. There is no object in insect anatomy 

 that is more easily identifiable than these breathing tubes, 

 or more easily demonstrable, and hardly any that forms 

 a more beautiful and attractive subject of study or 

 exhibition. 



(To be coiitiniU'd.) 



Noticts of Boofes. 



Xiiih and their i'nii<cnies. By Dr. W. Freaji, B.Sc, 

 LL.l). (George Bell and Sous, London.) This book 

 will form a welcome addition to the library of the scientific 

 farmer. It gives a brief account of the constitution of 

 soils in different parts of the British Isles, tracing them 

 back to their parent rocks, and describing, without too 

 much technicality, their more important physical and 

 chemical properties. A soil composed entirely of one 

 constituent rock frequently lacks the essential elements 

 of fertility. Thus a pure clay, a pure limestone, or a pure 

 sand is incapable of growing crops, whereas a soil con- 

 sisting of a suitable mixture of these ingredients is likely 

 to be very fertile. 



All gravel and sand is not the best land : 

 A rolteny meuld is land worth gould. 



The reason that alluvial soils are generally so fertile is 

 the mixed character they possess, owing to their having 

 been derived from the disintegration of various kinds of 

 rocks. Not uncommonly the admixture of a rock that 

 supplies the deficiencies of another takes place naturally 

 along the line of outcrop of two geological formations of 

 very different character. Dr. Fream's book is full of 

 .suggestions likely to stimulate the farmer to close observa- 

 tion of the processes of decay of rocks, of the action of 

 water, drainage, frost, and wind, and of the work of the 

 little micro-organisms which appear to act as the carriers 

 of nitrogen between the enormous reservoir of the element 

 contained in the atmosphere and the roots of plants. 



Mouiifintph (if the liiitish Cieadcr. (Parts 8 and 4.) 

 By G. Bowdler Buckton, F.R.S. (Macmillan and Co.) 

 In these two parts the genera and species from J>icrano- 

 trv/iis to Kudciiiithtix are described and illustrated, and 

 most of the largest and best known of our species thus 

 come imdor review. The dryness of descriptive details is 

 relieved in Part 4 by some exceedingly interesting matter 

 of a more general character, and questions such as those 

 relating to the sound -producing apparatus of the chirping 

 ('iriidif, and the condition of the organs of special sense in 

 the froghoppers generally, are ably discussed. The 

 attractive but little worked subject of life histories comes 

 in for a brief notice, though very little light can be thrown 

 upon it. There are great difliculties in the way of the 

 artificial rearing of insects such as these, which subsist 

 entirely on the juices of living plants ; and even when the 

 observer is- successful in keeping the insects alive in con- 

 finement for any length of time, the secrecy of some of 

 their operations, combined with the smallness of their size, 

 renders the task of watching them doubly difficult. Mr. 



Buckton records some interesting observations made on 

 the beautiful green Tettifionin riridis, Linn., one of the 

 handsomest of our species, a colony of which he kept for 

 some weeks under glass shades within which rushes wei-e 

 growing ; but even under such favourable conditions, he 

 failed to discover the mode of o\'iposition. A curious 

 figure is given of a mass of " cuckoo spit," which had 

 hardened into a reticulated ball containing the dead insect 

 within it. 



An lllustnited ll<iiidhii,,k „J Uritish J tnij/oiidies. By the 

 Editor of the " Naturalist's Gazette." (Naturalists' 

 Publishiag Co., Birmingham.) There are scarcely any 

 insects so misunderstood, popularly, as Dragonflies, and 

 to all who woitld like to laiow the truth about them, we 

 would recommend a perusal of this capital little manual, 

 in which the author has put together all that a beginner 

 needs as an introduction to the study of the group. There 

 are descriptions of all the British species, forty -five in 

 number, as well as an accurate account of their structiu-e, 

 habits, and life history, and instructions as to collecting, 

 preserving and rearing them. A number of excellent 

 illustrations, exliibiting most of our commonest species 

 and their transformations, adorn the pages, and will be 

 found a most useful aid to the student in his indentifica- 

 tions. We congratulate the author on having produced a 

 thoroughly useful and reliable little handbook, which will, 

 we trust, speedily find its way into the hands of many 

 entomologists. 



THE ANNULAR NEBULA IN LYRA. 



I'lV A. C. Raxvard. 



WE owe the photograph of the King Nebula in 

 Lyra, shown in the plate, to the courtesy of 

 M. Trepied, the Director of the Observatory 

 at Algiers. It is an enlargement from a 

 photograph taken by him with an exposure 

 of six hours in the principal focus of one of the 13-inch 

 achromatics which have been prepared by the Brothers 

 Henry for the international work of the photographic 

 siu-vey of the heavens. It was taken in August last, and 

 was one of the first-fruits of the instrument after it was 

 mounted at the Algiers Observatory. The photograph 

 w-as made with two exposures on successive nights, the 

 sensitive plate having been covered up and removed in the 

 meantime, and replaced when the instrument had been 

 brought into position by means of the finder with which 

 the driving is controlled. It has since been enlarged (J4 

 diameters, and the granulation of the original plate shows 

 very obviously ; the minute specks composing the nebulous 

 ring must not, therefore, be mistaken for stars. 



To the right hand of M. Trepied's photograph is a 

 photographic reproduction of Mr. Lassell's celebrated 

 drawing of the Nebula, made with his four-foot equatorial 

 in 1860. Mr. Lassell's drawing is turned with the North 

 point uppermost on the page, and the west or following 

 side towards the right hand, and the photograph is turned 

 to correspond in orientation with Mr.' Lassell's drawing. 

 The scale of our reproduction of Mr. Lassell's drawing is 

 l"=0-Oir) of an inch. It will be noticed that M. Trepied's 

 photograph shows the central star as nebulous, and the 

 rest of the field inside the annular nebula comparatively 

 dark and not filled up witli nebulosity as in Mr. Lassell's 

 drawing. The central star also appears nearly symmetri- 

 cally situated with respect to the elliptic ring of nebu- 

 losity, whereas in Mr. Lassell's drawing it is decidedly to 

 the north-east of the centre. In describmg it, Mr. Lassell 

 says : " The star a little below the centre of the dark 

 space in the Nebula is faint, and from its faintuess, in 



