Vízügyi Közlemények, 1947 (29. évfolyam)

1-4. szám - VI. Szakirodalom

(32) bed load material. During the experiments a number of arrangements were made the object of investigation; the solution, as shown in fig. 4jd and in -photograph 1 was finally satisfactory. A rubber sheet was fastened to the bottom of the entrance opening of the trap box, — fig. 5 — made of iron sheet, with springs, thus assuring a good position at the bottom. On the exit opening is a trap which automatically closes when the rope is taunt; thus the passing of water through the trap is possible only if it rests on the bottom. By opening the trap door an electrical current is brought into action, and therefore the time of the bed load measurement can be fixed by a signaling lamp. The bed load material may be emptied through the door on the side of the trap box quickly and without difficulty (photograph 3). Weight of the box is 90 kg. The device was checked at all stages. A fine sieve was mounted to the exit opening in order that the washed out material may be discerned (photograph 4). Two measurements were performed in this way at flood stages on the whole cross section of the Danube. At these occasions the Danube at the gage at Bratislava was only 83 and 118 cm lower than the highest stage so far recorded. The measuring device was a full success. It has been established that all load remained in the trap, even the finest sand; pains must be taken only that no more material is in it than indicated in fig. 7, since the .surplus is swept away by the water. Therefore it is advisable to leave the apparatus on the bottom for a longer duration at low stages only; at high stages the duration of observation may be 1 to 1 and y

2 minutes. On account of the pulsation of the water movement (fig. 8) the measuring conceals many an error, and therefore at least two measurements ought to be taken at the top and low oscilating points. For this reason the velocity of the water should be steadly registered during the measurement. From the sieve analysis curve of the material taken from the trap and the bottom when compared with each other it may be seen (fig- 9) that the trap collects the bed load material entirely, and therefore it may also be employed on rivers on which no traps with sieves could be used on account of the fineness of the material. The trap still remains to be calibrated in a laboratory which is a delicate and difficult problem. Since, however, the efficiency of the apparatus in all probability is very high it may be employed very well without comparing measurements. PROFESSIONAL LITERATURE. Dr. techn. L. Kreybig, Doz. : NATURAL FEATURES AND THEIR ASSERTIONS IN VEGETABLE PLANTINGS. Published by the Hungarian Agricultural Educational Association, Budapest, 1946, pp. 384. With colored regional agricultural map of Hungary, Scale: 1 : 750,000 (In Hungarian). D. C. 631.4 : 626.80 The chief motive of the author's book is, that in organizing and steering of plant cultivation the fundamental requirements are the knowledge of the natural features effective according to locality and extent of area and the demand of the plants. For this reason the author reviews in his book all natural features and rules which must be taken into consideration in Hungarian plant cultivation and rationalisation. The natural features regard to the climatic conditions of Hungary were treated from an agrarian-meteorological point of view by the National Meteorological Institute. On the regional soil units maps attached to the book these are shown by isothermas and isohyotals in accordance with the data of Dr. D. Berényi and Dr. A. Réthly. On the other hand the soil features and soil characteristics concerning plant cultivation are indicated in the maps published by the soil research section of the Geological Institute surveyed under the supervision and in accordance with the intentions of Dr. Kreybig with soil and Cartographic data on hand. These maps published by the Geological Institute on the scale of 1 : 25,000 are for the purpose of soil review and are supplemented by detailed pamphlets showing the che-