THE FRESH- WATER LOCHS OF SCOTLAND. 423 



Embroideries on the curves were common, and were attributed to a 

 long swell on the loch, to the wash of steamers, and frequently to the 

 opening of lock-gates on the canal at Fort Augustus. 



With the view of gaining information on the effect of small variations 

 in atmospheric pressure, a Dines's sensitive barograph was obtained.* 

 Records from an ordinary Richard barograph had indicated sudden 

 barometric changes as a frequent cause of seiches, and the records of 

 the sensitive barograph supported this view to a certain extent, although 

 on some occasions the loch seemed unresponsive to changes in atmos- 

 pheric pressure. On other occasions* however, the limnograph record 

 seemed to be an accurate reproduction of the record obtained by means 

 of the sensitive barograph. 



Loch Ness from its size proved to be rather unwieldy from the 

 point of view of seiches, so that when, in the summer of 1905, the 

 investigation of seiches was undertaken by Prof. Chrystal, he made 

 his headquarters on Loch Earn, and gathered much information as 

 to the cause of seiches from his observations.! 



NOTES ON THE DEPOSITS OF LOCH NESS. 



By G. W. LEE, D.SC., and L. W. COLLET, D.SC., with Analyses of 

 Selected Samples by A. WILSON, F.I.C. 



About sixty samples of the deposits covering the floor of Loch Ness 

 were collected by the members of the Lake Survey staff from various 

 parts of the loch, and were examined according to the methods used in 

 the Challenger Office for the study of marine deposits. 



They may be classed as follows : 



(1) Dark grey mud, from the deep basin opposite Urquhart bay ; 



(2) Ferrugineous mud, from the part of the Invermoriston deep basin 

 opposite Horseshoe craig ; 



(3) Peaty mud, from the south-west end of the Invermoriston deep 

 basin ; 



(4) Yellow-grey day, from off Inverfarigaig and off Cherry island; 

 and 



(5) Brown sand, from shallow water off Urquhart bay. 



* The purchase of this instrument was facilitated by a grant from the Moray Bequest 

 to the University of Edinburgh. 



f For further details the reader is referred to the following papers : " On the Hydro- 

 dynamical Theory of Seiches, with a Bibliographical Sketch,", by Prof. Chrystal, Trans. 

 Roy. Soc. Edin., vol 41, p. 599 (1005); Calculation of the Periods and Nodes of Lochs 

 Earn and Treig, from the Bathymetric Data of the Scottish Lake Survey," by Prof. 

 Chrystal and E. M. Wedderburn, Trans. Roy. Soc. Edin., vol. 41, p. 823 (1905); "An In- 

 vestigation of the Seiches of Loch Earn by the Scottish Lake Survey/'; Part I. " Limno- 

 graphic Instruments and Methods of Observation," by Prof. G. Chrystal ; Part II. " Pre- 

 liminary Limnographic Observations on Loch Earn," by James Murray, Trans. Roy. Soc. 

 Edin., vol. 45, p. 361 (1906). 



