14 



NATURE 



[March 3, 1910 



pallon. There are several other recipes, but nothing 

 enablinjjf one to decide which is the best. 'J'he mode of 

 action is even more obscure ; indeed, the whole subject 

 was in a state of confusion until Mr. Pickering took it 

 in hand and began to evolve something like order. 



The reaction between copper sulphate and lime is 

 shown to vield four basic sulphates : — (a) 4CuO,SO, ; 

 (fe)5CuO,S03; (c) ioCuO,SO, ; {A) ioCuO,SO,,CaO ; 

 and two other compounds {e) CuO,2CaO (existence 

 doubtful); (/) CuO,3CaO. The conditions of the 

 formation of each of these basic sulphates were inves- 

 tigated and a series of the corresponding Bordeaux 

 mixtures prepared. 



The properties of the sulphates were studied, 

 and in particular their decomposition under the influ- 

 ence of water and carbonic acid in presence of calcium 

 sulphate or of organic matter, these being the condi- 

 tions obtaining on the leaf surface. The next problem 

 was to ascertain the function of Bordeaux mixture 

 and so to settle which was the most useful of the 

 possible basic sulphates. These salts are, of course, 

 insoluble and have to be converted into a soluble sub- 

 stance before they can exert a fungicidal action. Nc 

 evidence could be obtained that the plant leaf or the 

 spore excreted anything that would dissolve an in- 

 soluble substance, but it was shown that the carbonic 

 acid of the air decomposed these basic sulphates in 

 accordance with the following reactions : — 



(a) ioCuO,2-5S03 + 375CO.,-375(CuO)2.C02 + 2-5CuS04. 



{b) ioCuO,2S03 + 4C02^4(Cu())2,C02+2CuS04. 



(t ) loCuO.SOa + 4 •SCaO = 4-5(CuO)2,C02 + CuSOj. 



(a) ioCuO,S03,3CaO + 7-5CU2=4-5(CuO)2,C02 + 



3CaC03 + CuS04. 



The copper sulphate thus liberated constitutes the 

 active part of the mixture. It acts in two ways. It 

 directly poisons the fungus cell developing from the 

 spore. Some of it gets into the leaf, displacing a 

 certain amount of iron and entering into a remark- 

 able combination not yet investigated, which seems so 

 long as it persists to afiford the leaf immunity against 

 fungal attacks. Further studies of this remarkable 

 body will be awaited with interest; it will be remem- 

 bered that Church isolated a pigment turacin contain- 

 ing copper from certain genera of the family Muso- 

 phagidae, but no such pigment is known in the 

 vegetable kingdom up to the present. But to return : 

 the object of the fungicide is to furnish a steady 

 supply of copper sulphate, and therefore the compound 

 (a) is the most efficient of the series. In the case of 

 (d), the ordinary Bordeaux mixture, a secondary re- 

 action sets in between the calcium carbonate and the 

 copper sulphate which further reduces its efficiency, 

 (a) is, however, physically less suitable than (c). The 

 whole leaf surface of the tree has to be covered with 

 the mixture, and consequently the more bulky the mix- 

 ture the better ; since (c) occupies more than four times 

 the volume of (a) it makes the most economical 

 fungicide in practice. From the fruit-grower's 

 point of view this compound has the further 

 advantage that it can be made on the com- 

 mercial scale and sent out as a paste ready 

 for use. The paste has been extensively tried 

 in orchards, with results that have completely con- 

 firmed the laboratory experiments. Several interesting 

 side-issues were followed up. Some of the compounds 

 in the ordinary Bordeaux mixture and in the so-called 

 soda Bordeaux, obtained by mixing copper sulphate 

 and sodium carbonate, contain copper in the electro- 

 negative condition, i.e. in the acid radical, and were 

 called cupricarbonates ; they appear to have no fungi- 

 cidal action, they combine with cellulose, and slowly 

 decompose to form cuprous oxide. 



The report will be found one of the most interesting 

 that has issued from Woburn. E. J. R. 



NO. 2105, VOL. 



5] 



UNDERGROUND TOPOGRAPHY IN IRELAND. 



THE e.xploration of caves has become an athletic 

 pursuit for certain enthusiastic specialists, per- 

 haps as a complement to mountain-climbing. The 

 results, however, have distinct scientific value, when 

 careful plans of the caves are made, and underground 

 waterways are traced. Attention has been directed in 

 these pages to the economic bearing of " spelaeology " 

 in the Juras, and the work of the geographer is ob- 

 viously incomplete, if his streams terminate, as so 

 often happens, in swallow-holes in a limestone area, 

 while others appear freshly on the surface, but may 

 prove to be old friends returning to the upper world. 

 Cave-research is arduous and often dangerous, and 

 the wonder is that such accurate observations are pro- 

 vided for us by men who have to work under cramped 

 conditions, and sometimes liberally immersed in water. 



The Royal Irish Academy (Proceedings, vol. xxvii., 

 section B, 1909) has recentlv issued two geographical 

 memoirs on Irish caves. The first (pp. 183-192, price 

 6d.) is by Mr. Harold Brodrick, on "The Marble 

 Arch Caves, County Fermanagh : Main Stream 

 Series." The principal cave was explored and de- 

 scribed by M. Martel some twelve years ago, with the 

 assistance of the Irish naturalist, Dr. H. Lyster 

 Jameson. Mr. Brodrick, with Dr. C. A. Hill, Mr. 

 R. Lloyd Praeger, of Dublin, and other workers, was 

 able to devote a longer time to the exploration of the 

 district. The training and experience gained by most 

 of the party in Yorkshire enabled them to add many 

 new points to the topography of the area. As Mr. 

 Brodrick remarks, the Marble Arch cave w'ill '" prob- 

 ably never become a show-cave, as the climb from the 

 foot of the Great Boulder Chamber to the end of the 

 Pool Chamber Passage is not one to be rashly under- 

 taken." The by-paths of the recent exploration led 

 the adventurers into several difficult places, not to 

 speak of waters, where few will care to follow them. 

 A large-scale map is provided, on which, however, the 

 names used in the text are not always to be found. 



The second paper (pp. 235-68, with four plates, 

 price 15. bd.), on "The Mitchelstown Caves, County 

 Tipperary," has a wider general interest. The 

 authors are Messrs. C. A. Hill, H. Brodrick, and A. 

 Rule; but Mr. R. Lloyd Praeger took part in the 

 exploration. The New Cave, between Mitchelstown 

 and Cahir, is probably the best-known cave in Ire- 

 land ; but the plan now given of it seems to be far 

 more accurate than that published by M. Martel, and 

 includes several passages and chambers previously un- 

 recorded. The work may not have been so exciting ns 

 that among the unfathomed waterways of Fermanagh, 

 but one and a half miles of cave and passage have 

 been mapped out. A curious point is that the names 

 "Demon Cave" and "Victoria Cave" were found 

 chalked up in some of the unrecorded portions, and 

 these have been adopted in the plan. The names in 

 this plan, by the bye, require one or two corrections 

 to bring them into agreement with the text. The 

 account of the New Cave might have been rendered 

 even more complete by a reference to Prof. Car- 

 penter's paper on its fauna in the Irish Naturalist 

 for 1895. 



Still more interesting is the description of the 

 smaller Old Cave, which had apparently not been 

 visited by tourists since 1833. The plan now given, 

 covering 479 yards of cave and passage, is the first 

 that has been made. 



The clay of the cave-floors, which, as all visitors 

 know, renders them unpleasantly slippery, is described 

 on p. 267 as derived by inwashing from the Old Red 

 Sandstone; but the quartz crystals noted in it, which 

 are so common in the Carboniferous Limestone, and 

 its general character as a terra rossa, make it 



