548 



NATURE 



[Oct. 4, 1888 



Dr. Walker said he saw an obelisk on top of a hill struck. 

 The top was knocked off, and the fluid came from the steps of 

 the monument at fourteen different points, ploughing up the 

 ground, and breaking rock at 100 feet distance. 



Mr. Wood thought the black flash shown in one of the 

 photographs was due to the reflection of one of the other 

 flashes. 



Lord Rayleigh said Stokes attributed that to the combination 

 of gases in the path of the flash causing an opaque stratum. . 



Prof. Lodge said he could not understand why a conductor 

 should have such a good earth. Why did not three points do 

 at the bottom as well as at the top ? If properly constructed 

 conductors never failed, how was it that the hotel at Brussels 

 was burnt, for that was considered protected in the most 

 orthodox way? He would not say that conductors were of no 

 use ; they were of great use, but not absolutely certain. In his 

 experiment he was bound to adopt the plan he did, because the 

 experiments could not be done in any other way. It was only 

 the outer surface of the conductor which conducted, and 

 there was no particular good in the centre of a rod. A 

 tube would do as well, and would be all the better if opened out 

 into a flat bar, and yet better than that would be a strand of 

 wires. Iron buildings, to be safe, must have perfect connections, 

 for the smallest gap might give off a spark. That was the 

 danger in houses supplied with gas ; if the fluid travelled along 

 the pipes and came to a gap, a spark and a fire might result. 



Mr. Preece said the points between Prof. Lodge and himself 

 were reduced to a very small compass indeed. He himself had 

 always been a great advocate of iron on account of its cheapness. 

 The use of copper caused needless expense in the erection of 

 lightning-conductors. He believed every private house could be 

 protected in accordance with the recommendations of the Con- 

 ference for £1, if people would buy a coil of stranded iron wire 

 a quarter of an inch in diameter, with the finial points, and have 

 that put up. 



The President summed up the discussion, and said the 

 principal thing for them to pay attention to was that prevention 

 was better than cure. There could be very little doubt that the 

 presence of a considerable number of conductors afforded a great 

 deal of protection to the area in which it existed, as was shown 

 in the instance of Paris. It was desirable, if possible, that the 

 whole country should be overed with conductors to prevent the 

 discharge of flashes. There was no doubt that, though there 

 might be room for improvement in the conductors, they had on 

 the whole been right. 



THE INTERNATIONAL GEOLOGICAL 

 CONGRESS. 1 



II. 



T N order to understand the present status of the Con- 

 ■*■ gress, and to forecast its probable future, we must 

 briefly note the work done at the two preceding meetings, 

 and compare that with the general results of the meeting 

 just closed. At Bologna the greater part of the time was 

 occupied with discussions upon the exact meanings to be 

 attached to various geological terms, and upon the general 

 principles which should guide us in geological classifica- 

 tion. Certain rules were then laid down, which probably 

 few authors have consistently followed, and which it is 

 unlikely will be universally adopted. At Berlin the dis- 

 cussions turned more upon precise questions of classifica- 

 tion, especially those relating to the sedimentary rocks ; 

 upon the lines by which various groups of strata should 

 be marked off ; and, in some cases, upon the names by 

 which these groups should be known. This change of 

 procedure was necessitated by the progress made with 

 the international geological map of Europe; the material 

 for such discussion on classification having been provided 

 in the shape of Reports from various national Committees, 

 of which that from England, presented by Prof. Hughes, 

 was by far the most complete. 



At the London meeting the classification of the Cambrian 

 and Silurian strata was fully discussed ; and two other 

 questions, only lightly touched upon before, were here 



1 Continued from p. 526. 



considered in some detail— the nature and origin of the 

 crystalline schists, and the upper limit of the Tertiary 

 system. 



In Bologna numerous votes were taken, in Berlin several, 

 but in London none The English geologists were in a 

 majority sufficiently large to carry any point upon which 

 they were fairly well agreed, but no attempt was made to 

 test this ; and Prof, de Lapparent, in presenting a Report 

 from the Committee appointed by the Council to con- 

 sider the question of voting, paid a generous tribute to the 

 English members for their self-restraint. There can be 

 no doubt that the adoption of this Report marks an 

 important epoch in the history of the Congress, and 

 that resolutions hereafter voted will carry more weight 

 than those which at present stand on its records. It 

 recommended that members of the country in which the 

 Congress meets should vote separately from the foreign 

 geologists : if the votes of the two groups agree, the ques- 

 tion will betaken as settled ; if they disagree, the further 

 consideration of the question will be postponed. The 

 resolution further recommended that votes should not be 

 taken on questions which are purely theoretical — such 

 questions to be simply discussed, and various views ob- 

 tained ; and that decisions of the Congress should only 

 refer to the more practical questions. 



Two Commissions of the Congress have existed since 

 the Bologna meeting — that on the Map of Europe, and 

 that on Nomenclature and Classification. The work ot 

 the former is plainly marked out, and much has yet 

 to be done. The other Commission has, however, 

 in many respects served its purpose : it has obtained 

 Reports from the various national Committers, most 

 of which have been ably summarized by Prof. Dewalque. 

 The future work of the Congress will partly lie in 

 discussing these Reports, and in deciding such questions 

 in general classification as may apply to wide dis- 

 tricts, leaving minor points to be worked out by each 

 country for itself. A Commission was therefore appointed 

 with altered and somewhat wider powers ; its functions 

 will more fully shape themselves at the Congress in 

 Philadelphia. As the future progress of the Geological 

 Congress lies so much in the hands of this Commission, 

 it may be desirable to record here the names of its mem- 

 bers, which are to some extent the same as those already 

 given (p. 519) for the Council of the London meeting, 

 but there are some additions and changes: — Germany, 

 Zittel ; Australia, Liversidge ; Austria, Neumayr ; Belgium, 

 Dewalque ; Bulgaria, Zlatoski ; Canada, R. Bell ; Den- 

 mark, Johnstrup ; Spain, Vilanova ; United States, Hall ; 

 France, de Lapparent ; Great Britain, Hughes ; Hungary, 

 Szabd ; India, Blanford ; Italy, Capellini ; Mexico, Cas- 

 tillo ; Norway, Kjerulf; Netherlands, Calker ; Portugal, 

 Delgado ; Argentine Republic, Brackenbusch ; Roumania r 

 Stefanescu ; Russia, Inostranzeff ; Sweden, Torell ; Swit- 

 zerland, Renevier. Prof. Capellini was elected President 

 of the Commission ; and Prof. Dewalque, Secretary. 



The Report upon the Map of Europe was presented to 

 the Congress by Dr. W. Haucbecorne. This stated the pro- 

 gress which is being made. Four or five sheets of Central 

 Europe will be ready for publication during the next two 

 years, and it has been decided to publish the sheets as 

 completed, each with its own title and index, instead of 

 waiting for the completion of the whole of Europe, as 

 was at first intended. A proof sheet (C iv.), containing 

 a large part of Northern Germany, was exhibited ; on 

 this there are twenty-four different tints for the sediment- 

 ary formations, three for the Archaean, and nine for the 

 eruptive rocks. The map is on the scale of 1 : 1,500,000, 

 and will consist of forty-nine sheets. One colour is taken 

 for each great group — Cretaceous, green ; Jurassic, blue - r 

 &c. The subdivisions are shown by various modifica- 

 tions of these colours. As a rule, the lower subdivisions 

 are shown by the darker tints, so that the map may be 

 read with more facility than is usually the case with geo- 



