484 EEPORT— 1893. 



then brought to light, together with the supei-ficial deposits in the sur- 

 rounding district. The results obtained by him may thus be briefly 

 summarised : — 



(a) Section : 



Feet 



1. Soil and gravel ) gQ 



2. Boulder clay \ 



3. Fine sand, stratified ........ 20 



4. Shelly clay, bottom not reached 7J- 



(h) Chemical analyses (1) of the shelly clay, (2) of the overlying- 

 Band, and (3) of the brown clay, 233 yards south-west of the ' main 

 section,' by Mr. W. Ivison Macadam, Edinburgh, were given. 



(c) A list of the organic remains (comprising several Arctic shells), 

 determined by Mr. David Robertson and Mr. T. F. Jamieson, was pub- 

 lished. 



(d) From the character of the deposit and the condition of the organic 

 remains, as described by the foregoing authorities, Mr. Fraser inferred 

 that the shelly clay was in situ, and indicated a depression of the land to 

 the extent of over 500 feet prior to the deposition of the overlying 

 boulder clay. 



In 1886 Dr. H. W. Crosskey made an examination of the shelly clay 

 and glacial deposits in the Nairn Valley ; his conclusions confirmed those 

 previously published by Mr. Fraser.' 



Recently several objections have been raised ^ against the acceptance 

 of these conclusions, so that further investigation became desirable. 



IV. — Detailed Examination of the Shelly Clay and Associated 

 Deposits by the Committee. 



The shelly clay is found at or under the base of a prominent broad- 

 topped ridge of drift on the south bank of the Cassie Burn, which there 

 flows along the foot of a bluff cliff of glacial deposits (see photo- engravings. 

 Plates II. and III.). This conspicuous ridge is traceable for upwards of 

 two miles in a north-easterly dii-ection, parallel with the river Nairn, and 

 for about 1,200 yards in a south-westerly direction. About200 yards nearer 

 the river, and nearly 100 feet lower, occurs a narrower ridge, along the top 

 of which runs the Craggie and Cawdor road for more than a mile. These 

 parallel ridges of drift are flanked on the south-east sides by marshy or 

 alluvial hollows ; indeed, at the point where the shelly clay occurs the 

 Cassie Burn flows for some distance along the hollow separating the two- 

 ridges. Both ridges have an irregular fall of about 50 feet per mile 

 towards the north-east ; the upper ridge being nearly uniform, and the 

 lower one irregular in its fall. 



A. — Excavation of 'Main Tit.'' 



The Committee began their examination of the shelly clay by 

 excavating a large pit or trench at the base of the cliff on the south bank 

 of the Cassie Burn. The site of the pit was 430 yards distant from the 

 junction of the Cassie Burn with AUt Buadh. At the outset the length 

 of the trench was 25 feet and the breadth 15 feet at the surface, but a& 



' Trans. Inverness Field Club, vol. iii. 



■• Trims. Geol. Soc. Glasguw, vol. ix. ; Brit. Assoc. Bej'., 1892, p. 714. 



I 



