»5S 



NA TURE 



[December 13, 1894 



segmenting egg between slide and cover-slip leads to the forma- 

 tion of a flat plate of blastomeres, and Dr. Graf's observations 

 coincide completely with those of Driesch up to the 32-ceIl 

 stage. .\t this point the author determined to remove the 

 pressure exerted by the cover-slip, and to notice the effect pro- 

 duced on the egg by this reversion to normal conditions. To 

 his astonishment he found that, after removing the pressure (by 

 gradually adding a surplus of water between slide and cover- 

 slip) the various blastomeres began to fuse together again. In 

 this way a plate of 15 cells was produced, each cell containing 

 two and, in a few cases, three nuclei. Shortly afterwards the 

 separate nuclei in each cell reunited. The last transformation 

 observed by the author was the conversion of the plate into a 

 I2cell stage, consisting of eight micromeres and eight micro- 

 meres. The results of the experiment are full of interest, and 

 well worthy of renewed trial. The author is certain that 

 the fusion of the blastomeres took place quite regularly : the 

 two or three daughter-cells of one mother-cell reunited to form 

 the single uni-nucleated equivalent of the mother cell again. 



Certai.n obscure phenomena connected with the mingling of 

 two masses of liquid are dealt with by Herr E. Kaiser in the 

 current n^xahnol Wiedemann' s Annalcn. Two soap-bubbles 

 or two jets of water when brought into immediate juxtaposition 

 will not always mingle at once, and sometimes they will not do 

 sj at all. Impurities in the water or soap solution will 

 encourage fusion, and so will a difference of potential. Whether 

 the influence of the latter may be explained on the supposition 

 of sparks breaking down the intervening layer of air, is a ques- 

 tion which has been answered in the affirmative. But Herr 

 Kaiser's experiments tend to show that in reality the difference 

 of potential simply increases the pressure on the intervening 

 air, and forces it out at the sides, thus diminishing the distance I 

 between the two surfaces down to the radius of molecular | 

 action. He suspended a circular film of Terquem's sugar-soap 

 solution in a wire ring by a delicate spring balance, and brought 

 a bubble to bear against it from below. The film and bubble 

 were placed in electric connection through their supports, and 

 differences of potential due to I, 2, 3 and more Daniells were 

 subsequently introduced. With the films investigated, the 

 time necessary for fusion was about 3 '2 seconds with no differ- 

 ence of potential, i 4 seconds with one Daniell, and o'4 with 

 two. With more Daniells fusion took place instantly, and the 

 films burst in moit cases. The pressure was I "016 gr. The 

 displacement of air from between the films was studied by the 

 aid of the Newton's rings formed between them. The rings 

 widened out, rapidly at first, then more slowly, and the ming- 

 ling was heralded by the appearance of the grey-blue of the 

 first order. A difference of potential simply accelerated this 

 process. 



It has been said by someone, that a whole set of meteoro- 

 logical predictions may be disturbed by a cowboy carelessly 

 throwing down a burning match upon a prairie. The match 

 starts a prairie fire which ciuseschanges extending throughoutthe 

 atmosphere, and so an accident may upset the most carefully pre- 

 pired forecast. This is, of course, a far-fetched case, but it is 

 worth while knowing what effects great forest fires have upon 

 the atmosphere. To this end Prof. Cleveland Abbe, in the 

 Monthly Weather Revir.u, determines some of the meteorological 

 results of the extensive forest fires in the United Stales during 

 July and August of this year. It appears that, with regard to 

 their influence upon atmospheric moisture, the experience of 

 the past summer is suffi.-ient to show tliai forest fires are not 

 necessarily followed by rain, and are not a practical method of 

 inducing rain in dry scasoni. Comparing the normal maximum 

 effect of solar heat with the compulation of the effect of burning 

 fo.est. Prof. .\bbc finds that, in the locality where it occurs, a 



NO. 131 I, VOL. 51] 



forest fire can heat its atmosphere more than the hottest sun of 

 June, in the ratio of 10,000 to 750. Fortunately, however, the 

 general influence of the forest fire upon the whole atmosphere 

 is much smaller than that of the sun, because the fire is of 

 small extent, while the sun affects the whole earth. The 

 actual area covered by the forest fires of August in Minnesota, 

 Wisconsin, and Michigan did not exceed five thousand square 

 miles, whereas the area covered by the smoke, and, therefore, 

 hot air, from thcie fires before the heat was all lost by radiation, 

 was not less than one million square miles. A comparison of 

 the solar effect over this large area and the more intense forest 

 fire effect over the small area, shows that the foimer is fifteen 

 times that of the latter. Prof. .\bbe"s calculations thus afford 

 no foundation for the belief that forest fires have important 

 meteorological sequel*. The story of the connection between 

 careless cowboys and atmospheric circulation is, therefore, no 

 longer worth telling. 



The current number of V Elettricista contains a description 

 of a new method for measuring small resistances, due to Dr. 

 Pasqualini. This method, which requires no special app.aratus 

 that cannot be easily set up in the laboratory, consists in having 

 a coil, composed of a few turns of wire, wound double, so that 

 there are two similar circuits. This double coil is fixed to the 

 case of an ordinary galvanometer, so as to act on the needle. 

 The main current sent through the resistance to be measured 

 passes through one of the circuits of this auxiliary coil. .\ shunt 

 circuit to the resistance is formed by the second circuit of the coil, 

 the galvanometer, and a resistance-box. The connections are so 

 arranged that the main current and the shunt current in the 

 galvanometer coils tend to turn the needle in opposite direc- 

 tions. The resistance of the shunt circuit is varied till the 

 galvanometer deflection is zero. Suppose K is the galvano- 

 meter constant, while Kj is the constant which expresses the 

 effect of either of the circuits in the auxiliary coils on the needle, 

 and if I and / are the total main current and the fraction which 

 passes through the shunt circuit respectively. Then K i = K, I 

 - Kj », or if K is the resistance of the shunt circuit, the re- 

 sistance to be measured = ,— f'^- The value of the constant 

 Jv 



' can be obtained by performing the experiment on a known 

 K 



resistance. With an auxiliary coil consisting of two similar circuits 



containing four turns each, and a Wiedemann galvanometer of 8 



ohms resistance, the author finds he can measure a resistance of 



■0002 ohms within ^ I, using a standard ohm to detennine 

 1000 



the constant ' . 

 K 



In a paper communicated to the Physical Review, Mr. S. II. 

 lirackelt gives an account of some experiments he has made on 

 the magnetic properties of iridium. The samples used contained 

 9S per cent iridium, with some platinum, and a trace of phos- 

 phorus, but no iron. A bar of the metal 1 3 3 m.m. long, 

 32 m.m. wide, and 09 m.m. thick, when brought into the field 

 of an electromagnet, set itself at right angles to the lines of force, 

 and became permanently magnetised in a transverse direction, 

 and when suspended, freely set itself E. and W. The perme. 

 ability of a larger bar was tested, and was found to be unity ; 

 and although the specimen was sharply struck while in the mag- 

 netising coil, no induced magnetisation was produced. 



A NiiW illustrated descriptive price list of electric ami 

 magnetic apparatus, for use in colleges and scientific institu- 

 tions, has been issued by Messrs. Kmg, Mendham, and Co., 

 Bristol. 



We have received a Jahibuch containing the results of 

 meteorological obiervations made at the observatory of the 



