244 



NA TURE 



[July 12, 1894 



the many references to insectivorous insects ; for it is 

 quite as important that a cultivator should know what 

 insects to protect and encourage, as to recognise those 

 which it is to his advantage to suppress. Several of the 

 coloured plates afiord illustrations of the insect foes of 

 insect pests, and not merely of the familiar hymenop- 

 terous parasites, but of such friends to the cultivator as 

 the species of Syrphus which devours the cabbage aphis, 

 and of the Australian ladybird, a species of Novius, 

 which orange-growers both in Australia and in California 

 have found so effective an ally in keeping their groves 

 free of the dreaded cottony-cushion scale, Icerya Ptir- 

 chasi, Maskell. 



In noticing the first part of this work we appealed to 

 the author to add to its international value by append- 

 ing in every case the authority for the systematic name. 

 We are glad that Mr. French has been able to adopt 

 this suggestion. The agricultural entomologists of the 

 United States are great offenders in this respect ; indeed, 

 they sometimes give no systematic names to the in- 

 jurious insects which are made the subjects of their 

 bulletins, whilst they not infrequently coin trivial names 

 which are certainly not elegant, though they may be ex- 

 pressive. Hence it becomes difficult to know with any 

 degree of certainty what is the precise species referred 

 to ; confusion consequently arises, and the bulletin has 

 only a local value. In connection with the trivial names 

 themselves, there is room for improvement. For in- 

 stance, in the volume before us, descriptions are given of 

 the "green peach aphis" and the "black peach aphis"; 

 but as it is the aphis and not the peach to which the 

 colour refers, the names "peach green aphis" and 

 " peach black aphis " would be more descriptive. This 

 is no mere quibble, for in the volume itself the principle 

 is conceded in the name of the " cherry green beetle." 

 In the year 1892, when Plutclla crttcifcraruiii, Zell. — an 

 insect described in this volume as the cabbage moth — 

 wrought tremendous destruction amongst the cruciferous 

 crops of England and Scotland, the newspapers teemed 

 with descriptions of the ravages of the '' diamond-back 

 turnip moth." This naturally led to inquiries, perhaps 

 ludicrous, as to the nature of diamond-back turnips ; but 

 our Board of Agriculture set a good example by describing 

 the pest in an official leaflet as the "turnip diamond- 

 back moth," and thus reverting to the name by which 

 John Curtis made the insect familiar half a century ago. 

 We welcome this second instalment of a valuable 

 publication, and trust Mr. French may be encouraged to 

 bring to a successful conclusion a work of the highest 

 economic importance to agriculturists and horticulturists. 



OUR BOOK SHELF. 



''•■• 'iiti);! of the Ediiihurjfh Mathemutical Society. 

 Session 1883. (London: Williams and Nor- 

 ..... 1894.) 



From time to time we have noted the annual volumes of 

 this Society from vol. ii. to vol. xi., which appeared last 

 year. The volume before us fills up a lacuna and now 

 makes the series complete. In the early days of the 

 Society the publication of I'rotccdiiii^s was not con- 

 templated, and when an access of members rendered 

 publication possible, the cost of printing absorbed the I 



NO. 1289, VOL. 50] 



major part of the funds, and each session's subscriptions 

 have only sutiiced for the current session's volume. 

 Some few years since a special appeal was made and 

 funds sufficient to warrant publication obtained. The 

 result is the admirable piece of geometrical work before 

 us. For, in fact, the volume is almost entirely one man's 

 work. The first president was Dr. J. S. Mackav, whose 

 edition of Euclid for the Messrs. Chambers in 1SS4 gave 

 ample evidence that there was an elegant and specially 

 learned geometer in our midst. The article on " Euclid " 

 in the Encyctop. Britannica confirmed this discovery. It 

 has been long known that Dr. Mackay had large stores 

 of notes, and we are glad to find that he has found an 

 outlet for much of this interesting matter. At the second 

 meeting of the Society the president read a paper on the 

 triangle and its six scribed circles. A portion of this 

 paper was given in abstract in vol. ii., and was con- 

 siderably enlarged in vol. xi., under the heading 

 " History of the Nine-point Circle." In the long interval, 

 with the permission of the Council, Dr. Mackay has 

 amassed a collection of notes, divided into twenty 

 sections, filling more than 1600 quarto pages of manu- 

 script. A selection has been made which most nearly 

 corresponds with what was actually communicated to the 

 Society in 1883. The nine-point circle is accounted for 

 above. The sections embraced in the present instalment 

 treat of the centroid, the circumcentre, the incentrc, the 

 excentres, the orthocentre, Euler's line, relations among 

 the radii, and area. They occupy pp. 6-12S, and are 

 accompanied by sixty-eight lithographed figures. Each 

 property is traced back, as far as can be ascertained, to 

 the first discoverer, the author having had the assistance 

 of French, German, and Belgian mathematicians in ad- 

 dition to the aid of personal friends in Great Britain. 

 The result is a rich repertory of almost, if not quite, all 

 that is known on the special points indicated above. 



We sincerely hope that Dr. Mackay may be recouped 

 for the vast amount of work he has gone through, and 

 the expense to which he has been put, by an appreciative 

 and purchasing audience. This will encourage him to 

 put his remaining notes into the hands of some pub- 

 lisher, or possibly he may adopt the present mode of 

 publication. 



The only other paper is a collection of notes on 

 Pliicker's first equation connecting the singularities of 

 curves, by Dr. C. ("■. Knott. These are printed in the 

 form in which they were handed over to the committee 

 eleven years ago. 



The Starry Skies. By Agnes Giberne. (London : 

 Seeley and Co., 1S94.) 



This small book will be found a very useful addition to 

 the series in which it is published. It is written in a 

 clear and intelligible style, and should just suit those 

 young readers who wish to obtain some of the more 

 elementary ideas about the world on which we dwell, the 

 moon, and the planetary and stellar systems in general. 

 Great tact seems to have been shown throughout in the 

 choice of suitable examples for giving the reader a good 

 mental grip of distances, sizes, shapes, &c., of the 

 heavenly bodies, without over-burdening his or her mind 

 with too much detail. The clear print and the not too 

 liberal use of dark type render the book very pleasant 

 reading, while the cjuestions and answers at the conclu- 

 sion of each chapter will be serviceable. The illustra- 

 tions throughout are very good indeed ; the majority 

 of them being excellent reproductions from the more 

 or less important recent photographs. Among them 

 we recognise Roberts' .Andromeda nebula, the Pleiades, 

 a fine Orion picture, cluster in Hercules, and several 

 others nearly equal in quality. As a book for the young, 

 we can heartily recommend these pages on the starry 

 skies. \V- I- 1^ 



