November 13, 1919] 



NATURE 



277 



mentier, for irrigating orchards and market-gardens 

 in Syria, Palestine, and other countries subject to long 

 summer droughts. The observations of M. Parnien- 

 tier refer especially to the citrus gardens around Jaffa. 



In arid climates economy in irrigation-water is 

 obviously of the utmost importance. According to the 

 method proposed by M. Parmentier, the water is 

 applied direct to the roots of each tree bv means of 

 earthenware, cement, or iron pipes fixed vertically in 

 the soil. The great losses by evaporation that always 

 occur in open canals and in surface irrigation are 

 thus avoided. M. Parmentier remarks that with 

 vertical-pipe irrigation the water used in a citrus 

 orchard was only 84 litres per hectare, as compared 

 with 600 litres necessary for surface Irrigation, applied 

 every five to twelve days. At Jaffa there are 880 

 trees to i hectare (aj acres) of citrus orchard, and 

 1 100 plants in the banana gardens. These figures are 

 very high, and imply a great consumption of water. 



The method proposed by M. Pai mentier is not new. 

 Watering orchards by means of special drain-tubes 

 sunk vertically in the soil is an old practice at Mes- 

 sina, in Sicily, where it is chiefly applied to voung 

 plantations. This method of irrigation was lirst 

 described long ago by Prof. Giuseppe Inzenga, the 

 well-known .Sicilian agronomist and botanist. In the 

 AnnaXi di Agricultura Siciliana; and again bv F. 

 -Alfonso-Spagna in his "Trattato d'Irrigazione " 

 (Palermo, 1S77, p. 502). In my book of agricultural 

 chemistry (" Chimica ."Vgraria, Campestre e Silvana," 

 Napoli, 1902) this special method of drainage-irrigation 

 is again described. The catuso used by the Messina 

 gardeners is a conical earthenware pipe, about i metre 

 long, open at both ends. The diameter of the upper 

 opening is 15 cm. and that of the lower 10 cm., the 

 pipe thus holding about 12 litres of water. M. Par- 

 mentier proposes pipes holding 20 litres for use in 

 orchard irrigation. At Messina the upper end of the 

 catuso projects slightlv above the soil, the opening 

 being covered with a brick or tile. 



In the summer of 1889, at Portici, near Naples, I 

 experimented on two lemon-trees of the same age 

 and size, watering one in the usual manner and the 

 other by means of a drain-pipe sunk verticallv in 

 the earth. During that hot summer, in the sandy, 

 volcanic soil at the foot of Vesuvius, the difference 

 between the effects of the two methods of watering 

 was very apparent. The lemon-tree provided with the 

 vertical drainage-pipe prospered on a ration of water 

 about 50 per cent, less than that necessary for the 

 control tree w-atered from the surface. 



The sunk end of the drainage-pipe is made to rest 

 on loose stones or potsherds, which form air-chambers. 

 Thus clogging of the pipe is prevented, and the water 

 that is poured down gets well absorbed and distributed 

 just where the roots are more vigorously developing 

 and renovating their absorbing organs. 



The subsoil air-chamber is as important as the 

 water-pipe. During drought the deep aeration of the 

 soil, when moisture is sufficient, provokes the growth 

 of the roots and the renewing of the root-hairs. In- 

 creasing their power of absorption and at the same 

 time favouring deep-soil nitrification. The roots are 

 induced to develop chiefly around the reservoir of 

 moist, warm air, where respiration and growth find 

 favourable conditions, the network of young and 

 active rootlets thickening around the spot where the 

 watering is concentrated and nitrates are being 

 actively formed. The loss by evaporation and per- 

 colation is minimised. Moreover, the close air under 

 the foliage of the trees, as M. Parmentier remarks, is 

 maintained in a less damp condition than is usual 

 in the deeply shaded citrus orchards, where the 



NO. 261 I, VOL. 104] 



development of parasites and pests is much favoured 

 by the moist shade 



M. Parmentier observed that vegetables watered by 

 underground irrigation are more tender and of higher 

 market value than vegetables watered by submersion, 

 or by any other method by which the foliage, stalks, 

 and upper parts of the roots are wetted. Indeed, it 

 may be added that the wetting of the foliage increases 

 transpiration, and consequently the waste of water. 



By means of vertical-pipe irrigation dilute liquid 

 manure can be applied far more effectually and 

 economically than by the usual method of night-soil 

 manuring In the case of vegetables and fruit-trees 

 subsoil liquid manuring is also advisable from a sani- 

 tary point of view. 



In arid climates, and wherever the economy both 

 of water and of liquid nitrogenous manure is of special 

 consequence, the Messina and Parmentier method 

 of underground watering by vertical drainafje is much 

 to be recommended. Italo Gigltoi.t. 



Laboratory of .Agricultural Chemistry, 

 Universitv of Pisa, Italy. 



New Sources of Aluminium. 



I WAS much interested in the account given in 

 N.\TURE of October 23 of the new methods of extrac- 

 tion of aluminium from clays of the kaolin class 

 (formed from the denudation of volcanic rocks) by 

 means of nitric acid and electric furnaces in Norway. 

 When this source of production is generally adopted, 

 as no doubt it will be owing to the diminishing supplies 

 of cryolite and bauxite, it seems probable that the 

 vast quantities of "decomposed porphyry" discovered 

 bv the late Prof. Jacob during his geological explora- 

 tions in the Rockv Mountains (some of which have 

 been mistaken for chalk by prospectors) will then form 

 an inexhaustible source of supply for that valuable 

 metal. J. E. Bacon. 



The Barracks, Fulford, York. 



Radiation Temperature: Dew. 



The letter in Nature of October 23 on radiation 

 temperature from Mr. Spencer Pickering reminds 

 me that the theory oi the equilibrium temperature is 

 given by Clerk Maxwell in his little-known article on 

 Diffusion (" Ency. Brit.," ninth edition, p. 218). Max- 

 well shows that in still-air temperature 6„ a thermo- 

 meter will gain heat per sec. 4rCK(fl„-9,), where'C Is 

 the electrical capacity of the bulb, K the conductivity 

 constant for air; and that it will give up heat per 

 sec. .\R{9t-6), where A is the area of the bulb, R the 

 radiation constant, and 6 the temperature towards 

 which radiation occurs. If the bulb be spherical C = r, 

 its radius. Consequently, 



4;7rK(e.-0,) = 4;7r=R(e,-e), 

 or 



That is, the conductivity effect depends on the radius 

 of the bulb. Mr. Pickering has observed this in the 

 case of small bulbs. He goes on to apply this 

 result to small objects, such as the pistils and 

 stamens of flowers. I would like to point out another 

 effect to which his observations apply, namely, that 

 true dew (arising from radiation) is not found on 

 spiders' webs. If webs are examined when dew is on 

 the ground they are found to be dry. When drops of 

 water are found they arise from the collecting action 

 of the webs on mist or fog, i.e. by the collection of 

 drops already formed. I have confirmed this on many 

 occasions. I conclude that whenever drops are found 

 on webs it is the result of fog or mist. 



Sidney Skinner. 

 .South- Western Polytechnic Institute, Chelsea. 



