In searching for material built from cellulose which might, by the application of X-ray analytical methods, throw further light on the nature of the cellulose lattice and its orientation in biological structures, Sponsler (1930) examined the green alga, Valonia ventricosa , which grows in the form of a single-celled hollow sphere often as much as 2 cm. in diameter. From the X-ray Photographs which he obtained, he was able to show, not only that the cell-wall is composed of crystallites of cellulose which for such a substance must be considered as relatively well-developed, but also that these crytallities are so laid down in the wall that there is a preferential orientation of the crystal lattice with respect to the surface. The plane of "spacing" 6·10 Å. U. lies roughly parallel to the wall, while the plane, of "spacing" 5·33 Å. U. lies roughly perpendicular to the wall. On the other hand, Sponsler (1931) concluded that there is no further selective orientation of the cellulose crystallites, but that, "in attempting to determine, in Valonia , the position of the remaining axis, the (cellulose) chain axis, the diffraction lines which indicated the presence of the chains showed that a random distribution of the chains occurred around a radial reference line of the wall." By the courtesy of the same worker, the actual specimens on which these observations were made were soon afterwards submitted to an optical examination in polarised light by R. D. Preston (1931) of the Botany Department of the University of Leeds. His results appeared to offer a striking confirmation of those of Sponsler, for he found that the wall was divided approximately into areas forming a mosaic, each area having its own interference colour, different from that of its surroundings. The average size of the areas was about 1·5 × 10 -4 sq. cm., and the extinction directions in general varied considerably in passing from one area to another. Preston assumed, in accordance with what appears to be a well-established, but as the sequal shows erroneous, custom, that the extinction directions in any area were parallel and perpendicular to the directions of the cellulose chains in that area, and therefore concluded, since many interference patches would be irradiated simultaneously by an X-ray beam such as Sponsler used, that the effect of random orientation described by the latter was in perfect agreement with his own findings. The fact, however, that Sponsler had used for his investigations, not single pieces of cell-wall, but blocks made up of a large number of such pieces, suggested that there might be a fallacy in this argument, even though the blocks in question were so build up that meridians running from the hold-fast of the spherical cell were as far as possible parallel. In spite of the fact that the optical examination suggested the contrary, it was still possible that the X-ray diffraction effects had been produced by the accumulation, in the large mass of material used, of relatively slow variations of orientation distributed over the whole surface of the cell-wall. It seemed, therefore, that a more promising line of attack would be to take X-ray photographs of single pieces of wall and, if possible, limit the X-ray beam each time to a single interference patch which had been previously defined with the aid of the polarising microscope.
In view of the increasing importance of meteorological investigation, it has been thought advisable to place on record t h e following observations on the electric charge carried by rain of various types.The nor!< was done at Otago University, New Zealand, in t h e winter and early spring of ~3 2 2 , mosL of the observations being talien between the months ot' May and September. The season was unfortunately an exceptionally dry o n e ; but, in spite of this, certain interesting results were obtained which may help to throw sonie light on a problem which can be solved only by much witlespread observation. APP.\R.\TUSl'he apparatus used was similar to that described by Professor IIcClelland.' I'hc rain is caught in a shallow conical vessel A , 81.5 crn. in diameter, and zo.; cm. i n dcpth. made of 20-gauge zinc (see Fig. I ) . To i t is attached a suspension H , which carries the tipping bucket G . This is of thc ordinary kind, and is arranged to tip when 30 cc. of rain have entered it. C is n wooden bos measuring 106.7 cm. each way with a door on one side; it is provided with a zinc top, D, fitting o \ e r the box, nith a circular opening 78. j cm. in diameter, from which the zinc slopes downwards to throw off the rain.I3 is a strong gal\-anised-iron cylinder 9 1 . 4 zm. in diameter and 9 1 . 4 cm. hisli. The whole of the csternal part is permanently earthed 'io protect the receiver from the earth's electrostatic field. The receiver is conncctcd by high-tension magneto wire, insulated where it passes through the wooden bos and the roof, t o the electrometer in the room beneath. .-In electrometer reading u p to ~j o volts was used. The potential on the needle was 86 volts. It was found that with positive on the needle voltages over + 100 were not registered with accuracy though negative ones up to I.;O volts were. Also conversely with negative on the needle the instrument was unstable for negati\ e potentials over 100 volts. To overcome this the potential on the needle could be sivitched m e r to suit the occasion.The water discharged a t eacn tip of the buc1;ct is caught i n E and tToows out through a pipe upon a vessel, \-, which is pressed down, malting contact on a metal strip beneath and ringing a bell close to the observer. The vessel is perforated, allowing the water to e s c a y ; a spring then restores it to its first position and :!ie contact is broken. l'he electrometer is connected tG earth a t each rin;; of the bell, contact being made through the water which falls upon .a wide-meshed gauze just beneath the bucket. This gauze is earthed, therefore iince the stream of water i s continuous at this point thc receiver is earthed also. Proc, ti. Irish ;lcmf., 35, Sect. I\, .\pril, 1920, pp. 13-59.
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