2 90 SCIENTIFIC APPARATUS. 



pared, and illustrated as to convey a large amount of information 

 which cannot easily be given by mere written or spoken descrip- 

 tion. At the same time, by appealing to the eye, they stimulate 

 habits of observation. And apart from their advantage in respect 

 to geological teaching, they have a high value in general educa- 

 tion. Geological models are employed with much advantage in 

 making known the main features of geological structure. They 

 may be constructed with the view of specially illustrating such 

 phenomena as faults, or the inclination of strata, or the influence 

 of the irregular superficial removal of rock upon the line of out- 

 crop of strata, or the mode of occurrence of lodes and veins, or 

 the methods of working coal and other minerals. On the other 

 hand, models of particular and instructive districts are sometimes 

 of great value in bringing directly under the eye a combination of 

 geological features which may be readily grasped and understood 

 when so presented, but which could not be adequately realised by 

 the learner on the ground itself. Diagrams, it need hardly be 

 added, form an indispensable part of the apparatus of the teacher 

 of geology. They enable him to supplement his fossil collections 

 and make his pupils realise what were the forms and the structure 

 of extinct plants and animals. By bringing the facts of physical 

 geography and geology graphically before the eye, they not only 

 make them more easily apprehended, but fix them on the memory. 

 A well-devised and clearly-executed series of diagrams can hardly 

 be over-valued as an aid in teaching, and therefore as a means of 

 fostering the development of the science in the future. 



A. GEIKIE. 



