762 



NATURE 



[February 10, 192 1 



working the change-over switch the navigating 

 officer is able to detect, from the strength of the 

 signals in the coils, which side of the cable his 

 ship is on, as the signals will manifestly be loudest 

 in the coil nearest to the cable. 



The greatest length of leader cable in use is 

 forty miles. For a longer distance than this it 

 would be necessary to pay special attention to 

 decreasing the continuity resistance of the cable 

 and the capacity between the core and earth in 

 order to reduce the current attentuation. This 

 would probably lead to a very expensive cable 

 being required. So far experiments have not been 



carried out in a greater depth than 30 fathoms, 

 but there is evidence that as the depth of water 

 increases, the strength of signals to one side (say 

 300 yards) from the cable does not decrease so 

 rapidly as is the case directly over the cable, but 

 the motion of a ship does not materially affect the 

 reception of cable signals by her. It is also 

 possible for a ship to receive visual signals, 

 instead of audible ones, from a leader cable. In 

 that case electric lamps are lighted by the current 

 frpm the cable. But the visual system has not 

 besfen developed to such a practically useful stage 

 as the svstem described above. 



Lake Victoria and the Sleeping Sickness. 



ONE need not yet have reached extreme old 

 age to remember something of the extra- 

 ordinary interest excited by the discovery of the 

 great Victoria Lake and the unveiling of the 



Fig. I. — Fly beach on Daniba Isic ; a favr.urite breeding ground is. under tlie buslics .-it the gap on 

 f the right. From " A Naturalist on Lake Victoria." 



sources of the Nile by Speke and Grant. A wide 

 field for the imagination was opened up by the 

 news of a vast expanse of water, second only to 

 Lake Superior among fresh-water lakes, in the 

 interior of the African continent. Dr. Carpenter's 

 narrative enables us to substitute reality for 

 romance, and to make the acquaintance of a 

 country of great beauty and charm, marred, un- 

 fortunately, by the terrible plague of sleeping 

 sickness. 



The main object of the author in his visit to 

 the great lake was the investigation of the bio- 

 nomics of Glossina palpalis, the tse-tse fly which 

 carries the trypanosome of sleeping sickness. This 



^ " A Naturai'st on LaVe Victoria : with an Account r,f Sleeping Sickness 

 and the Tse-Tse Fly." By Dr t). D. H. Carpenter. Pp. xxiv-|-333+ 

 2 plates. (London : '1'. Fisher Unwin, Ltd , ig2o.) Price 28^. net. 



NO. 2676, VOL. 106] 



important work, which was carried on under the 

 auspices of the Tropical Diseases Committee of 

 the Royal Society, involved a residence of about 

 four years on one or other of the numerous islands 

 which stud the northern part of 

 the lake, preceded by a stay of 

 some months at Jinja, on the 

 mainland. The outbreak of war 

 in .August, 1914, caused an un- 

 fortunate interruption in Dr. 

 Carpenter's labours; for the ex- 

 igencies of active service kept him 

 employed in various parts of 

 (ierman and Portuguese East 

 .Africa until November. 1918, 

 when he was released from duty 

 and returned to L'ganda. 



In spite of this and other inter- 

 missions, the author has been able 

 to put upon record, as Prof. 

 Poulton remarks in his preface, a 

 really wonderful bodv of observa- 

 tions. The earlier chapters of his 

 work contain a useful risxime of 

 our present knowledge of the 

 natural history of G. palpalis in 

 its relation to other factors which 

 contribute to the spread of the 

 disease, such as the presence of 

 game. It is needless to say 

 greater part of this now inti- 

 mate knowledge we are indebted to the 

 admirably devised and painstaking observa- 

 tions and experiments of Dr. Carpenter him- 

 self, as may be seen at greater length in the 

 official reports of the Sleeping Sickness Com- 

 mission. It is satisfactory to know that the 

 author, as a result of his careful study of the 

 habits of the pest, sees some hope, if not of exter- 

 minating the fly in certain regions, yet of dim- 

 inishing its numbers to a point at which it may 

 cease to be dangerous. This, it appears, can be ._ 

 done by constructing artificial shelters which are ] 

 highly attractive to the fly, and systematically ■ 

 destroying the pup* that are formed therein. An ' 

 alternative plan, viz. the extermination of the 

 Situtunga antelope (Tragelaphus Spekei). the 



that for the 



