4(!2 



APPENDIX. 



I. On the Instruments requisite to a Geologist. 



THE construction of geological maps cannot be too 

 strongly recommended, though they should never see 

 the light ; since thus only is practical accuracy at- 

 tained. While such a map also saves pages of unin- 

 telligible description, tljere is much information that 

 can be conveyed in no other manner; as no confidence 

 can be placed in mere description, where more than 

 one rock is concerned. Thus also does it become a 

 test of the observer's fidelity ; while, if that which has 

 been accurately examined is easily detailed, so must 

 we distrust written reports of matters demanding 

 much attention and labour, if that which is compara- 

 tively easy has been neglected. 



But as such a map is sometimes the geologist's ob- 

 ject, he must commence by the careful choice of a 

 topographic one ; since., if defective or erroneous, it 

 becomes the source of much labour and much doubt- 

 ing. They alone who know the facility afforded by a 

 good map, and the vexations of a bad one, will appre- 

 tiate the importance of this object. It cannot well be 

 too large ; from the narrow extent of many rocks in 

 nature ; while it may often be necessary to enlarge 

 certain portions for this purpose. A multiplicity of 

 details is also indispensable. Roads, rivers, hills, 

 houses, and villages, form the reticulum for the geo- 

 logist's observations ; while, according to the number 

 and accuracy of these, will be the facility and the 



