Vízügyi Közlemények, 1936 (18. évfolyam)
Kivonatok, mellékletek - Kivonat a 4. számhoz
23 puzzolana, and Table III those with mortars similarly prepared. On the basis of the results so far obtained, it cannot be stated whether replacing a portion of the cement with trass or puzzolana increases the strength of the concrete chemically, or only improves the grading of the aggregates, thus making it possible to diminish the quantity of the cement. Natural cements as complementary materials increase the density of the concrete, but their employment for the purpose of reducing the quantity of cement has to be thoroughly considered in each instance. 5. The method of working the concrete with vibrators results in a higher density and reduces the water-cement ratio considerably, thus securing great strength with a relatively small proportion of cement. It is advisable to employ this method when constructing concrete works of great dimensions. In addition the writer gives a description of the vibrators (figs. 14 and 15). IV. STATISTICAL DATA ON THE TRAFFIC OF THE HUNGARIAN WATERWAYS IN 1935. By Dr. J. VÁRSZEGHY. (Pages 558—571). The traffic on the waterways in Hungary is definitely influenced by the amount of crops and by the water conditions of rivers. In the second half of this year navigation was impeded by a long period of low water stage following the extreme drought of the summer months. Ice conditions were not particularly disturbing. The crop of cereals was better than in 1934, but as supplies of the former year became exhausted, only small quantities were exported. It was necessary to import large amounts of corn. Data of the traffic on waterways are treated in five groups : 1. Traffic of river harbours. Table I contains data of 184 harbours on the Danube, 8 on the Tisza, 28 on the Balaton Lake, and 2 on the Sió Canal. (Goods traffic in the harbours, a) Danube harbours, b ) Tisza, с ) Balaton, d ) Sió harbours. Inscriptions of columns : 1. names of harbours ; 2. total quantity of goods registered and delivered, in quintals ; 3. the same for outland traffic ; 4. total traffic in 1935; 5. total traffic in 1934). The total traffic of the harbours amounted to 26 million quintals, which shows an increase of about 10 per cent compared with the previous year. In the inland traffic an increase of 16.6 per cent, and in the outland traffic a decline of 1.5 per cent can be stated. The traffic of the Danube harbours increased by 17%, while on the Tisza we find a decrease of 34%, owing to the scanty harvest. The traffic on the Bal aton Lake improved by 5%. Table II gives information as to the kinds of goods. The traffic of st°ne, gravel and other building materials predominates (item 8) by a total portio n of 33 per cent. The part of coal (item 9) decreased in the outland traffic, but incre ased by 21% in the inland traffic ; thus after all the total traffic, amounting to 25%, shows a slight increase. The 9 per cent traffic of cereals (item J) shows a decrease
