38 



Mr. J. Lilley on the Action of 



[March 8, 



errors to be found in meteorological registers. Eacb error creates con- 

 siderable confusion ; it throws doubt on the observations accurately made 

 at neighbouring places ; and that doubt cannot be removed except by the 

 continuity of the records at those places. This continuity is unattainable 

 unless the weather happens to be uniform over a wide district, or unless 

 observations are made at many more places than would be needed, if reli- 

 ance could be placed upon the accuracy of the observers. Another advan- 

 tage of self-recording instruments is that their records are independent of 

 particular scales. Their notation is in lines and curves that can be mea- 

 sured with equal facility according to any desired scale. The thermometer 

 lines could be measured at pleasure according to Fahrenheit's scale, as 

 used in England ; to the Centigrade, as in France ; or to Reaumur's, as in 

 Germany. The barometer lines could be measured with equal ease in 

 Enghsh inches, in millimetres, or in Paris feet. For the various reasons 

 we have mentioned, self-recording instruments are of eminent local and 

 international utility. The establishment of a series of them in England 

 would confer a wide benefit. They would give precision and fulness to 

 the charts of our own weather ; they would set an example that foreign 

 governments would soon follow ; and they would afford material in a very 

 acceptable form to meteorologists at home and abroad for the discussion of 

 the weather of Europe at large." 



II. On the Action of Compasses in Iron Ships.^^ By Mr. John 

 Lilley. Communicated by Sir W. Snow Harris, F.R.S. Re- 

 ceived February 9, 1866. 



Although many ably-written papers upon this subject have at various 

 times appeared, none of them seem to be of that simple practical character 

 as to supersede the necessity of any further investigation of the subject, or 

 deter the author from submitting to the Royal Society the results of many 

 years' practical experience in the construction of the mariner's compass, and 

 its adjustment in iron ships. These results are given with a view to ad- 

 vance our knowledge of this important and great practical scientific ques- 

 tion, and to add still more to the security of life and property. In the 

 present day, when iron shipbuilding is so widely extending, it is presumed 

 that the most humble offering tending to place the directive action of the 

 compass beyond the reach of disturbing magnetic forces may not be unac- 

 ceptable. 



It is unnecessary here to enter into a mathematical investigation of the 

 properties or magnetic condition of iron ships, this part of the subject 

 having been already fully treated and developed by many learned men. 

 The author rather proposes to confine himself to the consideration of the 

 probable causes of the disasters so frequently attendant on the navigation 

 of iron and other ships, through defective compass guidance ; such disasters, 

 according to the author's experience, may be traced, in a large majority of 

 cases, to one or other of the following causes : — 



