566 



NATURE 



[April i6, 1896 



with the models of telescopes, made especially for this purpose in 

 the mechanical department of the Grunewald-Sternwarte, will 

 form the foundation for an astronomical museum. It is requested 

 that every photograph shall be furnished with the name of the 

 observatory sending it in, also the exact particulars as to date 

 and time of exposure, method of developing, name of object, 

 and any thing of interest connected therewith. It would also 

 be desirable to state on the backs of the photographs, if, and 

 in what publication, any further particulars may be found con- 

 cerning the same subject. Though the exhibition opens on 

 May I, any pictures, which owing to the distance of the observa- 

 tory sending them, should not arrive by that date, can be 

 received at any subsequent period. As, however, a catalogue 

 is to be completed by July i, it will be to the interest of 

 exhibitors to see that their contributions arrive in Berlin on 

 July 15 at latest. Particulars as to the number and extent of 

 intended contributions should be sent as early as possible to 

 Herr F. S. Archenhold, Grunewald-Sternwarte, bei Berlin. 



The Sun's Rotation. — Two methods have hitherto been 

 chiefly employed to determine the period of the sun's rotation, 

 namely, observations of sun-spots and determinations of the dis- 

 placements of lines in the spectrum of the sun's limb. A third 

 method, depending upon the movements of faculse, has recently 

 been utilised by W. Stratonoff (^^A Nach., 3344). His results 

 are based upon an investigation of 400 photographs of the sun, 

 taken during 1891-1894, and the number of daily angular move- 

 ments available for discussion amounts to 1024, after rejecting 

 those in which identifications on successive photographs were at 

 all uncertain. All the facts which are brought together clearly 

 indicate that faculte in different heliographic latitudes move with 

 different velocities, and that the rate of movement diminishes in 

 passing from the equator towards the poles. In the zone 

 io°- 1 9° the retardation amounts to o°'37 per day as compared 

 with the equatorial angular velocity, while in the zones 20°-29° 

 and 30°- 40° it is o°'47 and i°'o respectively. The law of 

 variation of the velocity of the faculre with the latitude is much 

 more complex than in the case of spots ; from 0° to 8° the angular 

 velocity is almost constant, from 9° to 16° it decreases very 

 rapidly, between 16" and 25° it remains nearly uniform, while 

 from 25° to 34° it again diminishes quickly. Similar results are 

 obtained for both solar hemispheres. The faculse appear to move 

 more rapidly than the spots in all solar latitudes from 0° to 40°, 

 as shown by the following mean values : — 



Heliographic 

 latitude. 



Diurnal angle of rotation. 

 Facula;. Spots. 



0-9 ... i4'6i ... i4'30 



10-19 •■• I4'24 ••• 14'iS 



20-29 ••• I4'i4 ••■ i3"83 



30-40 ... 13-61 ... 13-40 



The spectroscopic measurements made by Duner indicate that 

 the photosphere rotates even more slowly than the spots, and 

 the following comparison shows the relation of the surface rotation 

 with that of the faculse : — 



Heliographic 

 latitude. 



Diurnal : 

 Stratonoff. 



Dun^r. 



o ... 14-61 ... 14*14 



15 ... 14-24 ••• 1366 



30 ... 13-87 ... 13-06 



So far as the available data permit any conclusions to be drawn, 

 it thus appears that there are three distinct laws of rotation for 

 what in all probability correspond to three different solar levels. 



THE TSETSE FLY-DISEASE.^ 

 "POR forty-six years the Tsetse fly has been notorious as 

 ■*- a terrible scourge to live-stock, and the most formidable of 

 impediments to colonisation in Equatorial and South Africa. 

 First brought into prominent notice by the explorers Gordon- 

 Cumming Oswell and Captain Vardon, it was described by 

 Westwood^ in 1850, under the name Glossina morsitans, from 

 specimens collected by the last-named traveller. The genus, an 

 ally of our common blood-sucking Stoinoxys, contains six 



1 " Preliminary Report on the Tsetse Fly-Disease, or Nagana, in Zulu- 

 land." By Surgeon-Major David Bruce, A. M.S. (Bennett and Davis, 

 Field Street, Durban.) 



2 Proc. Zool. Soc. Land., 1850, pp. 258-270. 



NO. I 38 1, VOL. 53] 



described African species, for all of which Tsetse appears now 

 to serve as a common name. 



The peculiarities of the fly and "fly-disease" have been made 

 familiar by most other African travellers, Livingstone, Andersson, 

 Chapman, Selous, &c. The Tsetse (Fig. i) is a dipterous 

 insect, of no striking appearance, grey, with darker stripes on 

 the thorax, and a pale or yellowish abdomen furnished with two 

 dark spots on the anterior portion of each segment ; it is rath er 

 larger than the house-fly, but is narrower when at rest, the wings 

 overlapping. The mouth-parts form a powerful, piercing and suc- 

 torial beak. Local in distribution, the fly occurs in numerous 

 detached regions of Africa south of the Equator, its headquarters 

 appearing to be along the Zambesi and its tributary the Chobe. 

 " Fly-country " is hot, moist and low alluvial ground, along river- 

 banks, covered with forest or scrub vegetation, and uninhabited 

 save by wild animals. Within its sharply-defined limits, which 

 may extend along one bank only of a river, the Tsetse swarms ; 

 it is extremely active, and eagerly attacks man or animals for the 

 purpose of sucking blood. On man no effect is produced beyond 

 temporary irritation, of which the extent has been ver>' variously 

 described, probably in accordance with the idiosyncrasy of the 

 victims. Wild animals do not suffer ; but domestic animals, 

 which have entered fly-districts, are seized in the course of a few 

 days with fever and wasting, and almost invariably die. Horses 

 and dogs rapidly succumb, while goats, donkeys and un weaned 

 calves are said by some travellers to be resistant ; this, however, 

 is not generally true of the two former kinds. Slight non-fatal 

 attacks confer no immunity, but some native breeds of dogs 

 enjoy partial protection, although a certain number of pups 



Fig. I. — A, Tsetse fly {Glossina sp.), Transvaal ; b, larva ; and c, pupariunit 

 of a Tsetse (after Bruce). 



in each litter perish. Books of African travel are full of 

 records of horses, teams of oxen, or herds of native cattle 

 having been destroyed by entering fly-districts, and on one 

 occasion a Masai army, proceeding to the attack of a neighbour- 

 ing tribe, was effectually routed by having incautiously crossed 

 fly-country. 



For some years the accounts of fly-disease were not seriously 

 questioned, until in 1870 a Mr. St. Vincent Erskine ^ endeavoured 

 to show that it was due solely to change of grass or climate, and 

 severely criticised Livingstone's account, forgetting that the 

 proper course lay in attempting to reconcile the apparent dis- 

 cordance between his own and other observations. Since then 

 Hartmann, Marno, Falkenstein and other travellers who found 

 either the fly present and disease absent (as on the Loango 

 coast), or the reverse, have further discredited the earlier state- 

 ments, and so eminent a dipterologist as Van der Wulp,^ in 

 summarising the evidence, has concluded that the Tsetse is not 

 injurious, or that its ill-effects are exaggerated. Nevertheless 

 travellers, especially in the Zambesi district, whilst adding 

 nothing to our knowledge, have constantly reaffirmed the 

 connection between the fly and the disease. 



One or two naturalists have indeed hit the truth, and among 

 them Schoch, who in an ably-reasoned little paper ^ concluded 

 that the facts pointed, not to the action of a specific fly-virus, 

 as was originally supposed, but to the transmissipn of a bacterial 



1 Paper read before the Nat. Hist. Assoc, of Natal, Teported in The 

 Entomologist, v. p. 217. 

 - Tijdschr. Ent., 1884, pp. 143-150. 

 3 Mitth. Schiveiz. ent- Ges., 1884, pp. 685-686. 



