October, 1903.] 



KNOWLEDGE. 



233 



a species of tsetse-fly is a carrier of the disease. Parasites 

 of the genus Trypanosoma — the active cause of nagana, 

 or tsetse disease — have been found in abundance, first iu 

 the cerebro-spinal fluid, and then in the blood tT victims 

 of the sleeping sickness. As it was obvious that the 

 parasites could not be conveyed from man to man, an 

 insect carrier was assumed, and suspicion fell on the tsetse. 

 Subsequently tsetse were discovered iu abundance in 

 Uganda, although previously not supposed to exist there. 

 As the sleeping sickness is likewise new to the country, the 

 suspicion arises that tsetse may have been introduced 

 through the Congo and Aruwimi route from the west coast, 

 where sleeping sickness has long been endemic. 



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ORNITHOLOGICAL 



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Conducted by Harry F. Witherby, f.z.s., m.b.o.u. 



Vitaliti/ in Incuhated Eggs.— The disa'trous weather this summer 

 has conclusively shown the astounding vitality of eggs when much 

 incubated, i.e., eggs within a day or two of hatcliing but not chipped. 

 I suppose Juno 19th is the great Partridge hatching day, and that 

 date appeared this year to have been the climax of bad wcatlier. So 

 bad was it that hundreds, nay, probably thousands of Partridges, were 

 fairly driven off their nests, though, sad to relate, a few extra devoted 

 mothers remained at the nest and died. A great many of these 

 deserted eggs were gathered and placed under hens, and, I believe, 

 did badly ; but very many keepers left them alone, and wisely, for 

 the weather improved, and I know of many cases where the birds 

 returned to their nests and successfully hatched off. One particular 

 nest on this estate was deserted on the morning of June 19th. It was 

 carefully watclied, and the eleven eggs were stone cold for 4S hours. 

 Then the bird returned, and on the 25th hatched off nine eggs. — 

 Jos. F. Orben, Tavorham Hall, Norwich, 1-lth September, 1903. 



Bird Migration. — Mr. W. Eagle Clarke, so well-known for his 

 valuable work in connection with the study of the migrations of birds, 

 intends this autumn to spimd a considerable time on the Kentish 

 Knock Lightship This lightship is stationed some twenty-one miles 

 off the mouth of the Thames, and Mr. Clarke hopes to mike 

 observations there on the east to west autumnal movements of birds 

 across the southern part of the North Sea. It is much to be hoped 

 that Mr. Clarke's plucky venture will meet with great success, and 

 that his zeal and perseverance will be rewarded by opportimities of 

 making valuable observations. 



Oreen Sandpiper in Co. Mayo, Ireland (Irish Naturalist, Sep- 

 tember, 1903, p. 218).— Mr. Godfrey Knox records that he shot a 

 (Ireen Sandpiper on the Yellow River, Foxford, Co. Mayo, on June 

 .'iOth last. The Green Sandpiper is a rare autumn and winter visitor 

 to Ireland, and has not previously been recorded as occurring there 

 in sununer. 



British Gret/ Ooose (Zoologist, July, 1903, pp. 268-273).— Mr. 

 H. W. Robinson hero expresses his opinion tliat there is but one 

 species each of the Pink-footed, Bean, and White-fronted Geese. 

 He thinks " that the variations in plumage are merely due to age, and 

 perhaps sex may also have something to do with it, althougli I rather 

 doubt this latter statement." In the Zoologist for August (p. 315) 

 Mr. J. A. Harvie-Brown confirms Mr. Robinson's conclusions. 



On the Identifwation of some of the Birds mentioned bg AriMotle. 

 By T. E. Lones, M.A., Lt.D., ii.sc. (Zoologist, July, 1903, pp. 

 211-253.) — In tills article the author discusses and gives his conclusions 

 as to the identification of various bii-ds mentioned by Aristotle, the 



identification of wh-ch has caused much controversy. Mr. Lones 

 remarks that the genera and species of about ninety of Aristotle's 

 birds are fairly well known, and of the remainder— about eighty in 

 number — the genera only of about forty have been determined with 

 more or less success. 



All contributions to the column, either in the way of notes 

 or photographs, nhoul' be forwarded to Harry F. Witherby, 

 at the Office o/ Knowledge, 326, High Holborri, London, 



l^otiers of Booits. 



"Theoky of Ouservatioxs. " 15y T. X. Thielo, Director of the 

 Copenhagen Observatory. (London : Charles & Edwin Layton. 

 190.3.) — Every applied science, which is well developed, may be 

 divided into two parts, a theoretical (speculative or mathe- 

 matical) part and an empirical or observational one. Both are 

 absolutely necessary, and the growth of a science depends very 

 much on their influencing one another and advancing simul- 

 taneously. No lasting divergence or subordination of one to 

 the other can be allowed. The theoretical side deals with 

 accurate determinations and develops the form, connections 

 and consequences of the hypotheses. These hypotheses must 

 be changed as soon as they are seen to be at variance with 

 observations. The empirical side of the science procures and 

 arranges the observations, compares them with the theoretical 

 ]iropositions, and is entitled by means of them to reject, if 

 necessary, the hypotheses of the theory. But it is in itself 

 grounded on hypotheses. The form of the observations, and 

 the choice of the circumstances that are considered essential, 

 must be guided by theory. The present work deals with the 

 empirical side and investigates, not observations themselves, nor 

 the way in which they should be made, but the common rules 

 according to which they are submitted to computation. But 

 the first chapter on the " Law of Causality " will well repay 

 study by those who deal chiefly with the theoretical side. In it 

 there is especially matter for thought for the ultra-speculative, 

 for the metaphysicians who attempt to reason back to origins 

 and out to limits. Such attempts are simply blocked by such a 

 statement as the following : — " In order that an observation 

 may be free from every other assumption or hypothesis than the 

 Law of Causality, it must include a perfect description of all 

 the circumstances in the world, at least at the instant preceding 

 that at which the phenomenon is observed." Nor can the 

 assertion that " The Law of Causality cannot be proved, but 

 must be believed, in the same way as we believe the funda- 

 mental assumptions of religion, with which it is closely and 

 intimately associated,'' be e.^actly palatable to those — and there 

 are many such pseudo-scientists — -who make it their boast that 

 they cannot accept as true any proposition which is not demon- 

 strated or demonstrable to the intellect. 



" Design of Dynamos." By S. P. Thompson. (Spon.) 

 Price l'2s. net. — This excellent work, on the design of continuous 

 current generators, is well worthy of a place beside the other 

 well-known works of the same author on the electrical engineer's 

 bookshelf. The work is one which may bo regarded as supple- 

 mentary to the author's treatise on " D3namo-electric 

 Machinery," in fact it bears every appearance of an extension of 

 this work, and we shall be surprised if it is not shortly to be 

 found incorporated in a new edition of the latter. In his 

 opening chapter, on " Dynamo Design as an Art," the author 

 very properly points out, in the very first sentences, that dynamo 

 design, while depending upon certain fundamental .scientific 

 principles which can bo definitely laid down and taught with 

 precision, is essentially an art, and as such only to be acquired 

 by the aid of practice and experience. Profes.sor Thompson 

 expounds these scientific principles in his usual lucid style, and 

 in addition ho gives the dynamo designer the principal data 

 which he will reciuire, and a very good outline of the general 

 rules which have been gradually evolved from the accumulated 

 experience of many successful designers of these machines. 

 After this most necessary preliminary note of warning to the 

 reader, the author proceeds to the consideration of magnetic 

 data and calculations, and gives various useful tables, referring 

 in some cases to specific types, for the description of which 

 reference must bo made to his work on dynamo electric 

 machinery. We tliink that the author might with advantage 



