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XIV. — An Investigation of the Seiches of Loch Earn by the 

 Scottish Lake Survey. 



Part I. : Limnographic Instruments and Methods of Observation. By Professor 

 G. Chrystal. — Part II. : Prehminary Limnographic Observations on Loch Earn. 

 By James Murray. Communicated by Professor Chrystal. 



(MS. received July 16, 1906. Read July 16, 1906. Issued separately October 17, 1906.) 



PART I. 



In this communication some account is given of the various instruments used in the 

 survey of the seiches of Loch Barn, of the methods of observing, and of the reduction 

 of the results of observation. 



Ill Part II., which immediately follows, Mr James Murray gives an account of the 

 preliminary survey, of which he had charge. Later, a summary will be submitted to 

 the Society of the results as regards the periods and nodes of the lake ; and finally, an 

 account will be rendered of the observations made in order to connect the occurrence 

 of seiches with other atmospheric phenomena. 



The Direct- Action Waggon Recorder Limnograph. 



From certain peculiarities in the limnograms obtained on Loch Ness and Loch Treig, 

 it was suspected that the Sarasin limnographs in the possession of the Lake Survey 

 might not be sufficiently sensitive to record faithfully the seiches of small amplitude 

 which Mr Wedderburn's preliminary observations had led us to expect on Loch Earn. 

 Also it was desired, if possible, to work three limnographs simultaneously — one near the 

 uninode, one near the binode, and one at one of the ends of the lake. I therefore 

 designed a new limnograph, intended so far as possible to avoid the principal defects 

 which had been noticed in the Sarasin instruments during the somewhat rough usage 

 which they had experienced in Loch Ness, but more particularly on Treig, where firm 

 installation and effective shelter was difficult to attain. The defects in question were 

 mainly three : — ( 1 ) Multiplicity of connections and gearing from which it proved 

 impossible permanently to eliminate back-lash ; (2) Friction of sliding parts ; (3) 

 Difficulty of adjusting the recording pen so as to avoid shake, blotting and tearing of 

 the paper, and clogging of the pen. 



The design adopted was a modification of the band transmission of Plantamour's 

 limnograph. 



TRANS. ROY. SOC. EDIN., VOL. XLV. PART II. (NO. 14). 51 



