CORRESPONDING SOCIETIES. 745 



counts any good advice that may be given to students as to precision in the use 

 of terms. It is perhaps too late to change, but it would have been better if the 

 chemists had adopted technical terms for the two groups of elements, instead of 

 applying the term metal to a material so unlike the ordinary idea of a metal as 

 is sodium. 



Geology has been a particularly flagrant sinner in the misuse of popular 

 terms. Its nomenclature has not only unconsciously absorbed and modified 

 many English words, but committees of experts have deliberately committed 

 such wholesale piracy that our language has been left bankrupt in some depart- 

 ments. Thus terms are needed in stratigraphy for the various subdivisions of 

 the sedimentary rocks and for the lengths of time occupied in their deposition. 

 The International Geological Congress proposed the following series of terms, 

 beginning with the larger divisions : — 



Formation. Equivalent Time. 

 Group Era 



System Period 



Series Epoch 



Stage Age 



Although this scheme of nomenclature would be very useful, it has not been 

 generally adopted ; and I think the reason is that, by assigning definite meanings 

 to all the indefinite terms available, there is nothing left for use in an indefinite 

 sense. Thus a number of beds which together may be either larger or smaller 

 than a subdivision of a system, cannot be called a series without risk of mis- 

 understanding. All the above eight terms are required for use in geology with 

 their current English meanings. The scheme proposed by the International Geo- 

 logical Congress involves using these words sometimes in a technical and some- 

 times in a non-technical sense. In literature the difficulty may be overcome by 

 printing the words with capital letters when they are used as the names of definite 

 divisions ; but that is impossible in speech. The principle recommended by the 

 International Geological Congress was excellent, but the scheme proposed has 

 proved impracticable owing to its application of old words to new things. 



Buckman adopted a sounder policy when he introduced the term Hemera foi 

 the time equivalent to a zone. 



Geologists have adopted some common words with meanings which render 

 geological phraseology unintelligible or even ludicrous to the man who has not 

 been warned that they require special interpretation. Thus the need in ele- 

 mentary teaching for emphasising the difference between mineral species 

 and mineral aggregates has led to the frequent use of the term mineral as 

 an abbreviation for mineral species. Some authors have been led by this 

 practice to deny that mineral aggregates are minerals, and therefore assert 

 that coal, most iron-ores, oil-shale, mineral oil, &c, are not minerals. Accord- 

 ing to that view the mineral industry has little concern with minerals; and the 

 mineral resources of the British Isles, which are generally regarded as extensive, 

 are reduced according to this nomenclature to practically nothing. 



Another triumph of dauntless logic is the use of the word rock. It is no 

 doubt convenient when speaking of the crust of the earth to have one term to 

 cover all its materials; and rock is used in this way just as the dust in the 

 atmosphere and the salts in the sea may be included with the air and the water. 

 Hence has arisen the geological convention of calling any large constituent of the 

 earth's crust a rock, quite regardless of the cohesion of its particles. G. H. 

 Kinahan, for example, in his ' Handy Book of Rock Names ' (1873) says, 

 ' Thus loose sand, clay, peat, and even vegetable mould, geologically speaking. 

 are rocks ' (p. 1) ; and on page 131 he includes ice among rocks. 



Now this use of the term ignores the very essence of the popular idea of a 

 rock. The term appears to be derived from the same word as crag, and the 

 essential quality of a rock is firmness. The parable of the man who built his 

 house upon a rock would need to be retranslated, and Shakespeare's ' He's the 

 rock, the oak not to be wind-shaken,' 10 loses its meaning if rock may be loose, 



10 Goriolanus, V., 2, 117. Cf. also Zangwill — 'Feeling solid-based upon 

 eternal rock.' 



