March 14, 1S89] 



NA TURE 



467 



Russia, dealing with the amounts of rain and snow in 

 the Governments of Kherson and Bessarabia (Memoirs of the 

 Odessa Society of Naturalists, vol. xiii. Part l). Pluvio- 

 metric observations were made in 1887 at 158 stations, and 

 1 160 descriptions of thunderstorms have been sent in. It 

 appears that the average yearly amount of rain and snow in the 

 Government of Kherson is about 41 1 millimetres (434 milli- 

 metres at Odessa), a line drawn from the mouth of the Dniester 

 to Orenburg separating the regions which receive more than 

 400 millimetres of rain every year from those in the south 

 which have less than that. The Caucasus shore of the Black 

 Sea, with its heavy rains (1500 to 2000 millimetres every year), 

 makes, of course, an exception to the rule. The rains and 

 the snow are usually brought to Bessarabia by cyclones, those 

 which come from the south bringing with them the heaviest 

 rains. No fewer than 96 per cent, of the cyclones which come 

 from Hungary and the Balkan Peninsula are sure to bring with 

 them more or less heavy rains to Kherson, and the li'<e is true 

 of 51 per cent, of those which follow a course to the south of 

 Odessa altogether. The approach of cyclone-; can be easily 

 foreseen, but the changes of weather are so sudden in South 

 Russia that storm -warnings ought to be given from Odessa 

 instead of St. Petersburg. 



An earthquake was noticed at Kasina, in Croatia, on February 

 23. At Aquila, in the Abruzzi, on February 28, five shocks 

 occurred between 4 and 5 a.m. No damage was done. 



A SLIGHT shock of earthquake occurred in Eastern Pennsyl- 

 vania on March 8. It was felt at Lancaster, Harrisburg, 

 Gettysburg, and their environs, and also at Wilmington 

 (Delaware), and several places in Maryland and New Jersey. 



Another beautiful instance of the formation of geometrical 

 isomers, co.iipounds precisely similar in constitution, and differ- 

 ing only in the relative position of their atoms in space, has been 

 discovered by Prof. Wislicenus and Herr Holz. The compound 

 in question is dibromide of crotonylene, C H3— C B ■;= CBr — CH3. 

 Crotonylene itself, CH3 — C^C — CH3, is the third member of 

 the acetylene series of hydrocarbons, and combines directly with 

 bromine to form a dibromide of the above constitution, which is 

 now shown to have its atoms arranged in space in the manner 

 CH3— C— Br 



II , the two similar groups being symmetrical to an 



CH3— C— Br 



imaginary plane lying between them. On atte npting, however, 

 to prepare crotonylene dibromide from the tetrabromide by abs- 

 traction of two atoms of bromine, or from one of the tribrom- 

 butanes, CH3 — CHBr — CBr^— CH3, by splitting off a molecule 

 of hydrobromic acid, quite a different substance was obtained. 

 Analyses indicated exactly the same empirical formula as before, 

 but the boiling-point was found to be about 3° higher than that 

 of the first isomer, and its behaviour with zinc dust was markedly 



}. different. These facts can only be explained on the supposition 



I that its arrangement in space differs in being centro-symmetrical, 



! CH3~C-Br 



II , and this second isomer is therefore termed iso- 



Br-C— C H3 

 crotonylene dibromide. Both compounds combine directly with 

 a further quantity of bromine to form the same crystalline tetra- 

 bromide, CH3— CBrj— CBr.j— CII3. In order to prepare the 

 ordinary compound, the equivalent of a molecule of liquid 

 bromine is allowed to drop from the fine jet of a dropping- 

 funnel into a quantity of crotonylene contained in a flask sur- 



•\ rounded by a freezing mixture, as crotonylene boils at 18° C. 

 The reaction is very violent, each drop producing loud hissing ; 

 the product is washed with soda, dried over calcium chloride, 

 and distilled. After two fractionations, the dibromide is obtained 



. boiling constantly between 146'' and 147°. On the addition of an- 



crystals of the tetrabromide. The iso-compound is best obtained 

 by dropping in a similar manner one molecular equivalent of 

 bromine into cooled monobrombutylene ; distillation of the 

 resulting product yields tribrom-butane. This is diluted with 

 alcohol, and a molecular equivalent of sodium ethylate added : a 

 most violent reaction again occurs with elimination of a mole- 

 cule of hydrobromic acid. On addition of water, the iso-com- 

 pound is precipitate:l as an oil, which, on drying and subsequent 

 distillation, is found to boil constantly between 149" and 150^ 

 Addition of another molecule of bromine resulted in the pro- 

 duction of octahedral crystals of the tetrabronide identical with 

 those given by the ordinary compound. On reduction of each 

 of the compounds in alcoholic solution with zinc dust, the plane* 

 symmetrical ordinary compound is much more rapidly attacked 

 than the centro-symmetrical iso-dibromide ; when the reaction 

 in each case was allowed to proceed under the same conditions 

 for one hour, 99"6 per cent, of the ordinary compound was con- 

 verted back to crotonylene, while only 60 6 per cent, of the 

 iso- had been attacked. 



The Bureau des Longitudes has just issued an extract from the 

 Connaissance des Temps (1890), for the use of schools of hydro- 

 graphy and aspirants to the grade of captain, either for coasting, 

 or ocean service, a recent resolution of the Minister of Marine 

 having rendered such an extract very desirable. It contains the 

 tables of the rising and setting of the sun and moon, and the 

 place of the sun and sidereal time at mean noon for each day of 

 the year. The moon's position is given only for every twelve hours 

 throughout the year, instead of for every hour as in the complete 

 edition, and the tables of lunar distances have been reduced to 

 one star for each day. The positions of only thirty of the 

 principal stars are given, as against 300 in the complete edition. 

 The tables of refraction, and corrections for parallax, are repro- 

 duced in full, as are also the tables for conversion of mean- 

 time to sidereal lime. The positions of the planets, Jupiter's 

 satellites, &c., have been entirely omitted. Useful extracts from 

 the data relating to tides already published in the Anttuaire 

 des Marees ere given, with instructions for their use. The 

 "establishment of the port" for every important port in the 

 world is given, as well as the unit from which the height of the 

 tide can be calculated. Our own authorities would do well to 

 follow the example of the Bureau des Longitudes, and publish a 

 similar extract from the Nautical Almanac. 



The Director of the Marine Biological Association reports- 

 that the breeding season of a large number of marine animals^ 

 has begun, and that embryologists may find ample opportunities- 

 for study at the sea-side. Of Teleostean fishes, the spawning 

 season of the herring has passed some time since, that of the 

 plaice and flounder is just over, whilst the whiting, whiting 

 pout, and merry sole {Arnoglossus megastoma) are now ripe. 

 Nudibranch Mollusks are now visiting the shores to deposit their 

 eggs, and large specimens of Z><?m tuber:ulata and Eolis fapillosa 

 may commonly be taken on the rocks at Plymouth. The 

 uncommon Capuliis hungaricus has been found with ova 

 attached. Among the Crustacea the common shrimp, the 

 prawn, and Pandaius annulicornis are hatching out, and the 

 surface net begins to show numerous zoea; of Porcellana longi- 

 cornis. The Nauplii of Balanus and of Copepods are also- 

 abundant at this season of the year. The trochosphere larvze 

 of Chaetopods ( Tercbella and Phyllodoce) are beginning to make 

 their appearance, and ova and larvae of Echinoderms are very 

 abundant, particularly the ova of Ophiura, and Bipinnaria and 

 Pluteus larvae of Asterids and Echinids. The gonophores of 

 the Ilydrozoa are for the most part well developed, and filled 

 with ripe ova during the coming month. 



At a meeting of the Royal Botanic Society on Saturday, a 

 branch of coffee thickly set with ripe fruit from a plant growing 

 in the Society's conservatory was shown. Dr, Prior mentioned 



