514 



NATURE 



[March 28, 1895 



■pressure of 36 lbs. on the square foot, which is equivalent to an 

 hoorly velocity of eighty-five miles. Thunder and lightning 

 occnrred at several places in the rear of the disturbance. 



The project of a great free public library in New York 

 City has just taken shape, and been adopted by the several per- 

 sons and boards of trustees interested. It contemplates the 

 union of the Astor, Lenox, and Til den funds, aggregating 

 8,000,000 dollars. The site of the library is not yet determined, 

 owing to some restrictions on the use of the block facing Central 

 Park, on which the Lenox Library now stands. This site is 

 preferred if available. Boston, with its 5,000,000 dollars free 

 library, just completed, has already taken the lead. Brooklyn 

 has in the library of the Pratt Institute the nucleus of an 

 admirable free library, for which a new building is nearly 

 ready. 



We are glad to learn of the continued growth and develop- 

 ment of the Brooklyn Institute, due in great measure to the 

 stimulus imparted by the Brooklyn meeting of the American 

 Association for the Advancement of Science List summer. 

 Since that time the membership of the Institute has increased 

 many hundreds, bringing it up to very near four thousand, and 

 making it one of the largest scientiAc associations in the world. 

 Plans for a new building and museum, to cost several million 

 dollars, have been for some time ready, and only await funds. 

 Probably work will begin during the present season. The site is 

 secured, and it is hoped that aid from the city will be obtained as 

 soon as the condition of finances justify it. Meanwhile the Insti- 

 tute, in its geographical section, is foremost in promoting far- 

 'eaching plans of exploration toward both poles. Besides the 

 arctic expedition mentioned in NATitRE last week (p. 48S), a 

 well-digested plan for antarctic exploration has been presented 

 by Dr. Fred. A. Cook, who is already familiar with travel in 

 the north. He proposes to start next. September, equipped fora 

 slay of three years, but with the intention of returning in two 

 years unless accidentally detained. It seems probable that the 

 expense of the expedition will be provided for, and that it will 

 be the best equipped that has ever ventured into that region. 



I.s the February and March numbers of the Geological 

 Magazine, Miss Agnes Crane gives an account of the results 

 of recent research on the geological distribution of the Brachio- 

 poda, and their bearing on the evolution of the group. The 

 si mple I'at'.riua of the Cambrian is regarded as the actual root- 

 stock of the group, and the descent of the chief lines is traced 

 from it, with some breaks here and there i from'imperfection of 

 knowledge. According to Beecher, almost all Brachiopoda 

 pass through a "patcrine" stage of development. I.itti^uhi, 

 which (in the proper generic sense) does not occur below the 

 Ordovician, passes in its development through a stage 

 in which it resembles its predecessor ObeUlla of the Cam- 

 brian, and the latter is said to have a transient "paterine" 

 stage. Terebrattiliiia is also stated to pass through a " lingu- 

 loid " stage, yet its branch is not regarded as derived from 

 Lingiila, but independently from Pateriiia. Numerous other 

 genera are dealt with, and the paper is illustrated by two plates, 

 one giving the genc.ilogic.il tree of the Brachiopoda, and the 

 other some examples of the relation of forms. 



There is an interesting note in the Rultelin of the Royal 

 Gardens, Kew, on the use of green glass in phnt-houscs. The 

 use of glass of a green tint has hien for half a century a 

 charac'.eristic peculiarity of the plant-houses at Kcw, having been 

 adopted in 1845-46 on the recommendation of Mr. Robert 

 Hunt, F. K.S., on the ground that while admitting light and 

 chemical power in the same proportions a? white glass, it 

 would obstruct the passage of those rays which produce scorch- 

 ng. Recent investigations h.ive, homvcr, shown that the 

 NO. 1326, VOL. 51] 



green glass used at Kew intercepts about one-half of the eft'ective 

 influence of ordinary sunlight on the processes of plant-life. Of 

 late years the increasing haziness of the sky, due to the smoke 

 produced by the rapid extension of Londonto the south-west, has 

 produced the same effect at Kew as the use of green gl.iss; and it 

 has become obvious that in the future the plant-houses must be 

 so constructed as to exclude as little of the available sunlight as 

 possible. Since 1SS6 the use of green glass has, therefore, been 

 discontinued in all the houses except the fern-houses and the 

 palm-house ; and, it having been proved by experiment that 

 even filmy.ferns thrive better under white than under green 

 light, if direct exposure to the sun is excluded, the use of green 

 glass will now be altogether abandoned at Kew. 



The action of light in producing an electric discharge through 

 a vacuum tube has been further investigated by Messrs. Elster 

 and Geilel, who communicated some very suggestive results to 

 the Berlin .Academy at a recent sitting. They used a " photo- 

 electric cell," consisting cf an exhausted glass globe with an 

 anode of platinum wire and a kathode of an alloy of sodium 

 and potassium in equivalent proportions, which is liquid at 

 ordinary temperatures. This alloy was illuminated by a beam 

 of white light from a piece of zircon rendered incandescent by 

 an oxy-coal gas blow-pipe flame. This was condensed and 

 made parallel, and then sent through a Nicol prism so as to 

 polarise it in a certain plane. It was then found that a current 

 passed through the cell on connecting its terminals with a bat- 

 tery giving some 400 volts. The strength of this current 

 depended very much upon the angle of incidence and upon the 

 plane of polarisation. It was greatest when the plane of 

 polarisation was perpendicular to the plane of incidence, i.t. 

 when the electric displacements constituting light took place in 

 the plane of incidence, and when the angle of incidence was 1 

 about tSo", i.e. the polarising angle of the alloy itself. The 

 phenomena have probably some connection with the fact dis- 

 covered by Quincke, that light polarised normally to the plaoe I 

 of incidence penetrates furihest into metallic sheets. I 



Ol- late years' the transmission of electricity through gases 

 has been attracting a considerable amount of attention, and 

 numerous papers have appeared dealing with this subject, one 

 of the last being by G. Vincentini and M. Cinelli. Their 

 paper, which appears in the Nui.no Cimenio (5) vol. xxxvi., deals 

 with the transmission of electricity through the g.is surrounding 

 a wire heated to redness by an electric current. The authors 

 first describe experiments they have made on a long platinum 

 wire surrounded either by air or carbon dioxide. The wire was 

 protected from draughts by a series of screens, and a movable 

 platinum electrode, connectcil to a quadrant electrometer, gave , 

 the potential of the air at different distances above and below 

 the heated wire. It was found that the potential assumed by the j 

 electrode connected to the electrometer was higher than the mean , 

 potential of the he.ited wire. When the current passed through 

 the wire was sulliciently intense to heat it to incandescence, the 

 potential of the insulated electrode when placed above the wire 

 did not vary with the distance from the hot wire to any sensible] 

 extent.'only the maximum electrification was attained at difl'erenl ' 

 times after starling the current, and the greater the distancej 

 from the liotjwirc the greater the lime which elapsed before the I 

 steady state was reached. When, however, the insulated elec-l 

 trodc is below the incandescent wire, the difference of potentilH 

 decreases very rajiidly with the distance, so that at 15 m.m. iti 

 almost vanishes. In order to cair)' on observations on otbert; 

 gases besides air and carbon dioxide, the authors have devised a^ 

 modified form of aiipaiatus in which Ihe incandescent wire \t^ 

 placed inside a globe w hich is silvered on the inside. This globe/ 

 has fourlubuli, Iwo of which serve for thcinlroduclionof Iheelec-j 

 Irodes for the hot wire ; while of the remaining two,|one adiDltlJ 

 the insulated electrode, and the other a wire which is connected to 



