31 



The clinometer consists of a graduated semicircle, the radius 

 corresponding to being parallel in the line of vision. In the 

 centre of the circle is an axis with a milled head, at one end of 

 which is a transverse spirit level, and at the other a radius 

 ending in a vernier, which passes over the graduation of the 

 circle, and is parallel to the base of the spirit level. Thus the 

 angle read off is the angle of dip of the line of vision. At the 

 other end is fixed a compass. 



93. Two clinometers, one in mahogany, and the other 

 in boxwood. 



Lent by the Geological Laboratory, Royal College of 

 1887. Science. 



The latter folds like a foot rule, and has a hanging brass 

 pendulum, and graduated semicircle within. The outside is 

 engraved with a table, by means of which the amount of fall for 

 any given dip can be calculated. 



94. Three clinometers and four compasses. Prices of 

 clinometers: 10s., 15s., 20s.; of compasses, 2s. 6d., 

 7s. 6d., 8s., and 20s. 



1880. Exhibited by T. H. and J. T. Letcher $ Co. 



One of the latter has a brass pendant. 



III. GEOLOGICAL MODELS ILLUSTRATING VOLCANIC 

 ACTION. 



95. Model to illustrate the formation of volcanic cones 

 when the ejected materials are of a fragmentary 

 character. 



Designed by C. J. Woodward, Birmingham and Midland 



1885. Institute. 



This consists of a large square table which is perforated in the 

 centre, and below is fixed a vertical tube, connected at the 

 farther end with an elastic tube leading to a pair of bellows. 

 This is worked by a handle, and sends a continuous vertical blast 

 of air up from the centre of the table. Into the side of the tube 

 near its point of emergence in the table is fixed another horizontal 

 tube, filled with sawdust which is supplied from an open box at the 

 side of the table from which the tube leads, and is continuously 

 pushed forward by means of an endless screw, which is turned by a 

 handle at the end. In this way a vertical shower of sawdust is 

 ejected from the pipe, after the manner in which fragmentary 

 material is ejected from the neck of a volcano. The manner in 

 which the material collects round the vent is thus demonstrated, 

 and by continuing the process with variously coloured sawdusts, 



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