S6 



SCIENCE-GOSSIP. 



to the success of tlie volume. To these are appended 

 a list of books and papers quoted or consulted, and a 

 list of the herbaria examined. Prefacing the flora 

 proper, is an important introduction dealing with 

 contingent subjects, such as Topograph)', Drainage, 

 Altitudes, Geology, Meteorology, Delineation of the 

 Botanical Districts, and Botanical Notes. There 

 is also a comparative table, extending over about 

 twenty pages, of the plants occurring in Kent 

 and the adjacent counties of Essex, Middlesex, 

 Surrey, and Sussex. Another iimportant fea- 

 ture is an flistorical Sunrmary of the 

 Botany and Botanists of the County, by Mr. B. 

 Daydon Jackson. The flora before us does not 

 include the Cryptogamia, but it is hoped Messrs. 

 Hanbury and Marshall may issue that section at a 

 future time. The situation of the county with regard 

 to the rest of the British Isles, and the great diversity 

 of soil and locality, render it one of the richest regions 

 in these Islands. There are recorded approximately 

 elex-en hundred and sixty species of phanerogams, 

 found growing within its boundar}'. It is especially 

 rich in orchidaceous plants, no less than thirty-three 

 of the forty-four British species being found. 



Rambles with Natzcre Students. By Mrs. 

 Brightwen, F.E.S. 323 pp., Sin. x 5|in., with 

 numerous illustrations by Theo. Carreras. (London : 

 Religious Tract Society, 1S99). 



This is one of Mrs. Brightwen's well-known, 

 pleasantly-written books for young people. Her 

 object is to induce those who have opportunity of 

 rambling through rural districts to observe and search 

 for the reasons of the many wonders of Nature 

 surrounding them. The book is divided into months, 

 and familiar objects for each are figured and accom- 

 panied by chatty explanations. The whole is beauti- 

 fully illustrated with a frontispiece and nearly one 

 hundred and fifty drawings. It is a book to be 

 recommended to the unscientific lover of Nature and 

 country lore, for whom it is intended. 



All About Birds. By W. Percival-Westeli.. 

 176 pp., 75in. X 5in. (London : Feathers Publishing 

 Co., Limited, 1899.) is. 6d. 



Considering the sweeping title of this little book, 

 we hardly wonder that the author finds it necessary to 

 commence his preface with an apology. One would 

 have thought it would not have been difficult to select 

 some other, which would have more correctly 

 described its contents. Its pages are occupied by 

 an apparent reprint of a scrap-book in which the 

 author seems to have pasted all sorts of newspaper 

 cuttings and jottings from other sources, which refer 

 to birds. Some are amusing and others probably 

 true. As an example we quote one on page 25. 

 "'Them eggs is mighty old,' remarked Uncle 

 Swayback to the waiter ; ' TU bet them's the Lays of 

 Ancient Rome, I've heard tell of.'" Again, the 

 ■author informs us that "a pelican's pouch is large 

 enough to contain seven or eight quarts of water." 

 Doubtless the author on issuing this literary eft'ort felt 

 as proud, as did " a hen when it laid a foundation 

 stone"; perhaps he may include this "fact" in his 

 next edition. 



Entomological Society of Ontario. Twenty-ninth 

 Annual Report, 1S98. 120 pp. gi X b\ in, Illus- 

 trated with 67 figs, and two portraits. (Toronto : 

 Warwick Bros. & Rutter, 1899). 



The portraits illustrating this Report are of two past 

 presidents, Messrs. W. H. Harrington, F.R.S.C, 

 and John Dearness, I.P.S.. There are many articles 

 of considerable mterest in this Report, which is very 

 fuUv illustrated, and Mr. H. H. Lyman's address. 



CONDULTED BV JAMES yUtCK. 



Coherers. — Branly has recently modified his 

 metallic disc coherer by substituting a row of balls, 

 I cm. diameter. These are found to be very sensi- 

 tive, but the sensitiveness greatly depends upon the 

 material of which the balls are made. Brass and 

 lead are useless, but by mounting ten balls of soft 

 iron, one above the other, an initial resistance ot 

 about 990 ohms is obtained. This is reduced to 60 

 by a spark of i'5 mm. passing at a distance of 10 

 metres. A slight shock sends the resistance up to 

 1 , 300 ohms, and a second spark brings it down again 

 to 80 ohms. Hard steel balls produce similar results. 

 A ball coherer, consisting of six hard steel balls, is 

 about equal in sensitiveness to a coherer of gold 

 filings. Care has to be taken, however, in regulating 

 the de-cohering tap or shock. A sensitive coherer 

 may also be constructed by , enclosing a drop of 

 mercur)' in a glass tube between two cylindrical brass 

 electrodes. 



Black Radiators. — The efficiencies of the various 

 black materials used in coating instruments for radiant 

 heat, have been investigated recently by Kurlbaum. 

 A bolometer is exposed to radiation from a standard 

 body in the shape of an orifice of a hollow cylinder of 

 brass, blackened inside and heated on the outside by 

 steam. This orifice may be covered by a diaphragm 

 on which is deposited lampblack, or platinum black, 

 kept at the same temperature. The radiation from 

 these sources may thus be directly compared. The 

 results are difl'erent. The absorbing, and therefore 

 the radiating, power of lampblack increases rapidly 

 with the thickness of deposit, while that of the 

 platinum black, although it also increases, does so 

 much more slowly. The results of the experiments 

 show that the latter is the belter for most purposes. 



Recorder of PHOTO.\fETRic Readings. — When 

 taking photometric readings the illumination of the 

 scale is generally a drawback, as the retina gets 

 fatigued and therefore temporarily less sensitive. To 

 overcome this disadvantage use has been made of the 

 following arrangement. A cylinder of wood is 

 mounted with its axis parallel to, and somewhat below, 

 the top of the photometer bar. At the end of a 

 spring, attached to the photometer carriage, a steel 

 point projects downwards nearly to the surface of the 

 cylinder. By means of a rachet wheel arrangement, 

 the cylinder can be advanced a certain angular amount. 

 The paper upon the cylinder is at the same time 

 punctured b)- means of a steel point. The observer 

 can thus take a series of readings. 



Multiple Images. — Some recent experiments of 

 Mr. Shelford Bidwell have shown that the undefined 

 im.age of a luminous object, produced upon the retina 

 of a normal eye appears to be composed of a crowd of 

 separate images of that object If say, the filament 

 of an incandescent lamp is looked at through a lens, 

 concave or convex, of about 15 cm. focal length 

 from a distance of a few feet, numerous separate 

 images of the filament are seen, some brighter than 

 others. The number of these images increases as the 

 distance of the observer from the lamp is extended, 

 or when the lens is placed farther away from the eye. 



