192 



NA TURE 



[Jan. i, 1885 



while sometimes such English words as " insect," 

 "spider," "scorpion" will be in one form of type, and 

 sometimes in another. These are trifles, but still they 

 are worth attending to, and they do not detract from the 

 general merit of this translation, which we would freely 

 place in the hand of any student. 



Bosnien, Land u/id Leute. By Adolf Strausz. 2 voir. 



(Vienna, 18S2-4.) 

 After the occupation of Bosnia and Herzegovina by 

 Austria in 1878, the want of an authoritative and com- 

 prehensive treatise on those hitherto neglected provinces 

 of European Turkey soon became manifest. This want 

 is fully supplied by the present work, on which the author 

 has been engaged for the last four years, and for the 

 composition of which he has qualified himself by re- 

 peated visits to the region he has undertaken to describe. 

 The first volume, issued two years ago, is mainly his- 

 torical and ethnographic, and embodies a complete history 

 of the country, from the arrival of the Slavs in the fifth 

 century, down to the Austrian occupation in 1878. 

 Special sections are devoted to the various ethnical 

 elements, Mohammedan and Christian Bosnians, Jews, 

 Albanians, Zinzars, and Gypsies. These are all ade- 

 quately treated, except the Zinzars (Macedo-Roumanians 

 or Kutzo-Vlacks), the account of whom is confusing and 

 even contradictory. The author seems unaware that 

 their true relations to the surrounding populations, and 

 especially to the Roumanians, now settled in Moldavia 

 and Wallachia, north of the Danube, have been placed in 

 a clear light by the recent investigations, especially of 

 Roesler and P. Hunfalvy. The volume concludes with 

 a series of social sketches, in which the habits and 

 customs, legends, traditions, religions, national aspirations 

 of the people are ably dealt with. The second volume, 

 whose publication was delayed by various causes till the 

 present year, is perhaps the more important of the two. 

 It contains a complete description of the provinces, their 

 geographical features, climate, fauna, flora, natural and 

 industrial resources, administration, present condition and 

 future prospects. On all these points the author speaks 

 with great authority, and brings together a vast amount 

 of information at first hand. Although bitterly opposed 

 to the Austrian occupation, he believes that the in- 

 habitants will eventually acquiesce in a step which political 

 considerations had in any case rendered inevitable. The 

 area of the country is given at about 52,000 square kilo- 

 metres, an estimate based on recent but still incomplete 

 surveys. The population, given by the Salname of 1877 

 at 2,047,000, was reduced by the census of 1879 to 

 1,158,000, of whom 448,000 were Mohammedans, 496,000 

 Orthodox Greeks, 209,000 Roman Catholics of the Latin 

 rite, and 3400 Jews. The work unfortunately appears 

 without either map or index, for which two meagre tables 

 of contents are poor compensation. 



LETTERS TO THE EDITOR 

 [ The Editor does not hold himself responsible for opinions expressed 

 by kis correspondents. Neither can he undertake to return t 

 or to correspond with the writers of rejected manuscripts. 

 No notice is taken oj anonymous communications . 

 [ The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 t iat it is impossihli otherwise to insure the appearance even 

 oj communications ontaining interesting and novel facts.] 



The Solar Corona and After-Glow 



THE inclosed extract fro a a letter from the Rev. A. W. 



Heyde, resident at Kailang in Lahoul, a hill state in the North- 

 Wesl Himalaya (X. Iat. 32 34' 10", E. long. 77° 4' 10"), 10,000 

 feet above sea-level, gives an interesting notice of the solar 

 corona and after-glow, and affords some reason for the inference 



hat the conditions producing these appearances have been per- 

 'istent, although they may not have been observed in the cloudier 



and more hazy atmosphere over the plains of India. Mr. 

 Heyde's letter is dated November 3 : — 



" The corona round the sun has been visible since my last 

 letter to you in July, whenever the sky was clear. It was nol 

 always equally distinct, but never entirely absent. It is beauti- 

 fully distinct to-day. The same has been the case with the 

 after-glow, which no doubt results from [the same conditions as] 

 the corona." 



The following extract from the same letter is also of interest : — 



" I think I have mentioned already, in former letters to 

 you, that since about twelve or fifteen years the latter half of 

 August and the whole of September and October have become 

 very unsettled as regards the weather, rain or snow occurring 

 now often during these months, which, as a rule formerly, were 

 a time of fine, clear weather. These untimely precipitations inter- 

 fere very unpleasantly with the haymaking and harvesting in the 

 valley now nearly every year, of which many complaints are 

 heard. ... A similar experience is made in Ladak and other 

 parts of the Western Himalayas. Officers who took part in the 

 triangulation of Ladak during the four or five seasons between 

 1S60 and 1870 say they never could have done their work if at 

 that time the sky over Ladak had always been so cloudy, and 

 the high ranges so frequently enveloped in clouds, as is now the 

 case." 



In corroboration of this last remark I may mention that the 

 hopes that had been entertained of obtaining a valuable series 

 of actinometric observations at Leh, for which purpose two 

 trained observers were deputed to that station rather more than 

 a twelvemonth ago, have been so far grievously disappointed. 

 The atmosphere of Leh was believed, on the reiterated assurance 

 of former residents, to be remarkable for its clearness and free- 

 dom from cloud and haze. From the actinometric registers 

 received during the past year, and the notes which accompany 

 them, this appears to be very far from the case. 



Henry F. Blanfokd 



Meteorological Office, India, 4, Middleton Row, Calcutta, 

 November 21, 1SS4 



Flying-Fish do not Fly 



Fi,YING-fish are incapable of flying for the simple reason 

 that the muscles of their pectoral fins are not large enough to 

 bear the weight of their body aloft in the air. The pectoral 

 muscles of birds depressing their wings weigh, on an average, 

 \ of the total weight of the body, the pectoral muscles of 

 bats -j-'tj, the muscles of the pectoral fins of flying-fish only jjV. 

 The impulse to which flying-fish owe their long shooting passage 

 through the air is delivered, while they are still in the water, 

 by the powerful masses of muscle on both sides of their body, 

 which are of much greater breadth than in the case of the herring 

 or any other fish of their own size. 



The "flickering of the fins." which Dr. John Rae (Xature, 

 December 4, p. 102), like many others before him, takes for a 

 rapid muscular movement of the pectoral fins, is only a vibration 

 of their elastic membrane, and is to be referred to the same laws 

 as those which govern the flapping of a tight-set sail when a 

 ship under a stiff breeze is driving close to the wind. The 

 flapping or vibration at once springs up whenever the sail gets 

 parallel to the wind. 



The more rapidly a flying-fish darts out of the water, the 

 greater is the momentum with which the air presses on its out- 

 spread pectoral fins. Should, now, the atmospheric pressure 

 induce these fins into a horizontal position parallel to the wind, 

 their vibration is a necessary result. Let the outspread pectoral 

 fins of a dead flying-fish be held horizontally before the open- 

 ing of a pair of bellows, and the fins will be seen to vibrate as 

 soon as the current of air passes under them. For full proofs of 

 the accuracy of these propositions I beg to refer to my paper, 

 " The Movements of Flying-Fish through the Air" (Leipzig, 

 1S78). 



Zoological Institut, Kiel, Dec. 15, 1884 K. Mobius 



Iridescent Clouds 

 In addition to the particulars given in Nature for December 

 iS, 1S84 (p. 148) of the brilliantly-coloured clouds, the fol- 

 lowing observations made here may be interesting. They 

 were visible every day from the 6th to the 13th instant, except 

 it be on the 9th, and at all times of the day, but only strikingly 

 noticeable near sunrise and sunset. The colours did not appear 



