4/0 



some. The broken cluster closes again completely as the grapes left grow so 

 much the larger. If the injured vine is to be pruned, this should be begun, 

 at the earliest, a week after the hail storm in order to see how far the plants 

 have recovered. In pruning, as much growth of the current year as possible 

 should be left. It is especially important not to force prematurely lower 

 eyes which promise fruit. By using precaution' at least twice as many eyes 

 are left on the vine above the real fruiting eyes as are needed in the follow- 

 ing year. 



The method of spreading nets of galvanized iron wire over the vines, 

 said to be customary in Piedmont, should be recommended for further test- 

 ing, as a means of protecting the vines from injury-. 



Recently many experiments have been tried with "cannonading against 

 hail." Nolibois^ developed the theory of this method. The water vapors 

 arising from the soil are condensed into clouds, the moist dense layers lying 

 lowest. When these lower layers are greatly condensed by the radiation of 

 the soil, the layers directly above them are cooled greatly, occasionally below 

 zero. Any shock is now sufificient to bring the overcooled mist to freezing 

 and precipitation. If the process is continued, there is a constant weakening 

 of the cold action in the upper cloud layers, resulting finally in rain. 



According to this theory, declivities would be more exposed to hail than 

 lowlands ; lime or sandy soil more than moist alluvial soil ; bare soil more 

 than forests; land more than lakes or the ocean. If superimposed cloud 

 layers could mingle one with another so that the temperature is more equal- 

 ized, and over-cooling hindered, the formation of hail might be prevented. 

 Attempts are now being made to produce such movement of the layers of 

 the air adjacent to the clouds, by the explosion of cannon. 



Another theory based on the production of whirlwinds resulting from 

 the mingling of cold air from the mountain with the hot, rising stream of 

 the valley*, likewise recommends cannonading against hail. In Italy numer- 

 ous shooting stations have already been formed, yet the reports are very 

 contradictory. More favorable reports on the cannonading of the air have 

 been sent from France^ 



1 Ungarische Weinzeitung 1896, No. 34. 



2 Rho, G., Le reti metalliche a dife.sa dellc viti dalla grasnuola. Bollet. d. 

 Soc. dei Viticoltori. Roma 1892; cit. Zeitschr. f. Pflanzenkrankh. 1894, p. 168. 



a Nolibois, P., Th^orie de la formation de la grele; cit. Hollrungs Jahresber. 

 f. Pflanzenkrankh. 1904, p. 73. 



•* Bordiga, O., Grandine e sari. Atti del R. Istituto d'incorraggiamento, Napoli, 

 Vol. II, 5 Sen 



6 Praktische Blatter f. Pflanzenschutz, herausg. von Hiltner, 1905, No. 11, 



