THE FRESH- WATER LOCHS OF SCOTLAND. 351 



where a sounding in 48 feet was taken about 50 feet from shore. The 

 area of the lake-floor covered by less than 50 feet of water is about 

 80 acres, or 51 per cent, of the total area. 



Temperature Observations. The following series of temperatures, 

 taken in the deepest part of the loch, show that the whole body of 

 water was practically uniform in temperature : 



Surface 48-2Fahr. 



25 feet 48-2 



50 48-0 



75 , 48-0 ,, 



90 48 



110 47'9 



The particulars regarding the lochs in the Beauly basin are collected 

 together in the table on p. 350 for convenience of reference and com- 

 parison. From this table it will be seen that in the thirteen lochs 

 under consideration, which cover an area of 5J square miles, about 850 

 soundings were taken, or an average of 146 soundings per square 

 mile of surface. The aggregate volume of water contained in the lochs 

 is estimated at 11,230 millions of cubic feet, and the area draining into 

 them is over 215 square miles, or 37 times the area of the lochs. 



GEOLOGICAL NOTES ON THE LOCHS WITHIN THE BASIN OF THE FARRAR. 

 By B. N. PEACH, LL.D., F.R.S., and J. HORNE, LL.D., F.R.S. 



The mapping of the western part of the Beauly basin by the 

 Geological Survey has only been carried southwards to the watershed 

 between Glen Strath Farrar and Glen Cannich, and hence the following 

 notes are confined to the lakes lying within the basin of the Farrar. 

 This area is entirely occupied by the metamorphic rocks of the High- 

 lands, which have been arranged in two divisions (1) an older series, 

 which has been correlated with the Lewisian or Archaean gneiss of the 

 West Highlands ; and (2) a group of crystalline schists, termed the 

 Moine series by the Geological Survey, which are regarded as altered 

 sediments, and are supposed to rest unconformably on the older 

 Lewisian gneiss. 



The members of the older series comprise hornblendic and biotite 

 gneisses and ultrabasic masses, together with crystalline limestone, 

 graphite schists and eclogites, which resemble the rocks of Lewisian age 

 in the neighbourhood of Glenelg. The Moine series includes two 

 prominent subdivisions (1) flaggy and massive quartz-biotite 

 granulites; and (2) muscovite-biotite schists, the latter probably 

 representing an argillaceous phase of sedimentation. In the basin of 



