32 



NATURE 



[November 14, 1895 



also of the sheaf form, which I have seen in storms directly 

 overhead, the flash being like two brushes discharging in op- 

 posite directions, recalling the classical representations of the 

 lightning in the hand of Jupiter. Robert Bridges. 



Vattendon, Newbury, November 8. 



An Early Reference to Hydractinia ? 



In Swammerdam's letter to Thevenot on the anatomy of the 

 Hermit Crab, there seems to be a reference to Hydractinia. The 

 passage ("Biblia Naturae," Leyden, 1737, i. 197) runs thus :— 

 " Maximas tamen omnes [conchas] Fiici marini qucedam species, 

 jmtictis vel apicibtis minutis assurgetts, obtegebat eousque ; ut 

 tota nonnullarum figura obscurata & deformata esset ; neque 

 spiralium, quibus gaudent, convolutionum ulla posset conspici." 



I venture to suggest that the words in italics fairly (though, of 

 course, not literally) correspond to the " chitinous crust covered 

 with numerous grooved and serrated spines" of Hincks (" Brit. 

 Hydroid Zoophytes," i. 23, 24). The obliteration by Hydrac- 

 tinia of the whorls of shells tenanted by the Hermit Crab is 

 well-known. Specimens showing such obliteration may be seen 

 in the Natural History Museum, South Kensington. 



Harringay, N. Henry Scherren. 



Rooks and Walnuts. 



Mr. Reid's remarks on rooks carrying off acorns, suggests 

 my mentioning that they are great depredators of my walnuts. 

 They come early in the morning, attack the walnuts on the 

 trees, and carry them off to an adjoining field, where they punch 

 a hole in the shell and extract the contents. 



They build on several groups of elms in Ealing, and on one 

 row of trees close to Christ Church they come regularly at 

 Christmas to see what repairs are required ; but one tree, which 

 has an electric wire running through it, they now entirely avoid. 



George Henslow. 



A Substitute for Sulphuretted Hydrogen. 



Has " Rusticus " (see vol. lii. p. 597) heard of liquefied HjS ? 

 I have tried it, and find it works admirably. Unlike ammonium 

 thio-acetate, it can be obtained from any of the usual chemical 

 •dealers; a bottle containing a poupd, = 11 cubic feet, can be 

 had for a few shillings. It is always on hand when required, 

 and entirely dispenses with the old HjS apparatus and its 

 abominations. A very great desideratum is the purity of the 

 liquefied gas. Chemicus. 



A GERMAN IMPERIAL INSTITUTE. 



IN his presidential address to the British Association 

 at Ipswich, reported in Nature on September 12, 

 Sir Douglas Galton referred to the efforts made by the 

 <]ierman Government and Municipalities to advance 

 scientific knowledge and promote research. In his state- 

 ment that the " Royal Technical High School" at Char- 

 lottenburg " casts into shade the facilities for education 

 in the various Polytechnics which we are now establish- 

 ing in London," he scarcely appreciates the radical dis- 

 tinction between the German and London institutions, 

 which accidentally bear the same name, but which are 

 wholly different in purpose and organisation. But his 

 remarks on the Reichsanstalt of Berlin are so suggestive 

 and so full of interest, that I was eager to have the oppor- 

 tunity of visiting the Institute, and was glad within the 

 last week or so to be able, during a brief stay in Berlin, 

 to make myself better acquainted with its work. 



The Institute, as its name implies, is an " Imperial In- 

 stitute," as distinguished from the Polytechnicum, which 

 is under the Government of the Prussian State. The Poly- 

 technicum, or Technical High School, has been already 

 ■described in Nature, and is one of a number of technical 

 universities situated in the several States which compose 

 the German Empire. The Berlin Institute at Charlot- 

 tenburg is by far the largest and the most completely 

 •equipped in Europe, and is already pronounced too small 

 for the ever-increasing number of students, now exceeding 



NO. 1359, VOL. 53] 



3000. In close proximity to this building in the Marsch 

 Strasse, a turning in the leading avenue through the 

 Thiergarten, the Physical-Technical Imperial Institute is 

 now being erected. When complete it will consist of 

 three detached buildings, in addition to separate resi- 

 dences for the Director and for some members of his staff. 

 Two of these buildings are already finished, but the third 

 is not yet erected, and pending its completion the work 

 of this section of the Institute is carried on in a portion 

 of the basement of the Royal Polytechnic. 



The work of the Institute consists of two separate, but 

 in some respects associated, sections. Section I. is de- 

 voted to pure scientific research, and Section II. to the 

 testing and standardising of different kinds of measuring 

 instruments. The Research Department is already 

 housed in the main building of the new Institute, which 

 has been planned especially for the purpose ; whilst much 

 of the testing work of the other department is still carried 

 on in the Polytechnic building. The united Institute is 

 under the general direction of Dr. Kohlrausch, and is 

 maintained at an annual cost to the Government of about 

 / 1 5,000. 



The Research Department of this interesting Institute 

 is housed in a three-storeyed building, consisting of a 

 basement, a main floor, and an upper storey. The con- 

 struction is in many respects peculiar. The walls, in- 

 stead of resting on separate concrete foundations, are 

 built into a concrete flooring two metres deep, which 

 covers the entire area of the building, so that the walls, 

 basement, and flooring are closely bound together. The 

 effect of this is that the building, if it vibrates at all, must 

 vibrate as a whole, and no one part is separated from 

 another. There is consequently no need for the isolated 

 pillars which are found in some of our English labora- 

 tories. But even this arrangement does not appear to be 

 perfect, and although the building is well set back from 

 the road, in which there is some traffic, vibratory move- 

 ments are not entirely avoided. The principal floor of 

 the building consists of a central room, used mainly for 

 experiments requiring constant temperature, surrounded 

 by a corridor which leads into a number of other labora- 

 tories for experiments in electricity, magnetism, light, and 

 heat. There are various interesting arrangements for 

 maintaining the constant temperature of the central 

 room, including the admission of light from the 

 top through a series of separated glass roofs. The 

 experimental work of the first section, or " Abtheilung," 

 is under the direction of three heads of depart- 

 ments, Drs. Thiesen, Jaeger and Lummer, who occupy 

 themselves respectively with investigations in heat, 

 electricity, and light. They are aided by a number 

 of permanent assistants, and by other workers who are 

 admitted into the Institute for the prosecution of some 

 special investigation. The members of the staff are 

 engaged entirely in research, and have no teaching 

 duties. The researches of the staff during the past year 

 comprise numerous investigations connected with the 

 determination of the expansion of bodies under heat ; 

 experiments with different kinds of thermometers, and 

 pyrometers ; electric and magnetic investigations ; and 

 photographic and photometric experiments. Short 

 notices of these researches, giving the results as 

 ascertained, are annually published. 



Section I. is occupied exclusively with the testing of 

 different measuring instruments. The makers of thermo- 

 meters, manometers, and pressure gauges of all sorts, send 

 their instruments to the Institute to be tested. Galvanic 

 elements, accumulators, arc lights, ammeters, electric con- 

 densors, resistance coils, &c., are being tested in different 

 parts of the building. No measurements connected with 

 weight or mass are undertaken, and the testing of the 

 strength of materials for builders and engineers is carried 

 on in other buildings in noway connected with the Insti- 

 tute. The number of thermometers alone sent to the 



