J 872.] 



President's Address. 



25 



recognize the great importance of an accurate international system which, 

 like the Latin of the middle ages, enables men of science in all countries 

 to speak the same language ; and for this international character they 

 think the Metrical system singularly well adapted. — In connexion with 

 this subject I may state that the " Parliamentary Copy " of the National 

 Standard of Length, which is intrusted to the care of the Eoyal Society, 

 has been examined and found to be in excellent condition: a very 

 small modification has been made in its supports, to meet the suggestion 

 of a possible cause of minute injury in the contacts of the bar with its 

 bearing-rollers. — As connected with the general science of the country, 

 I ought not to omit to remind you that your Home Secretaries hold im- 

 portant posts in the Official Scientific Commission which has not yet 

 terminated its labours. 



I would next allude to the scientific subjects which within the last 

 year have been introduced at your public meetings, and of which the 

 greater part will be further published in your t Transactions ' or your 

 ' Proceedings.' And as demanding my first notice in every point of 

 view, whether as referring to the name of the writer or to the subject of 

 which he treats, I cite the paper by Sir Edward Sabine on the measures 

 of the Magnetic Elements in the northern regions of our globe ; a worthy 

 termination to an unequalled series of arranged results of observation, 

 which must be adopted as the foundation for all future theoretical inves- 

 tigations of terrestrial magnetism. In connexion with this, I mention 

 Captain Evans's collection of the values of magnetic declination on nu- 

 merous points of the British coasts, the magnetic survey of the eastern 

 districts of France by Messrs. Perry and Sidgreaves, and Mr. Chambers's 

 determination of the magnetic elements and their changes, and of the 

 lunar inequalities of magnetic declination, at Bombay. At the last 

 Anniversary of the Society attention was called by my predecessor to a 

 paper by Dr. Hornstein on the existence of a magnetical inequality 

 whose period is sensibly the same as the length of the sun's synodical 

 revolution, and which therefore seems to show that different parts of the 

 sun's surface produce different effects on the magnet. The examinations 

 of observations and the discussions of them within this Society have 

 confirmed Dr. Hornstehi's observations for the year in which he ob- 

 served ; and they have added this remarkable result, that in each year a 

 species of inequality appears to have been sufficiently recurrent with the 

 sun's revolution to show itself clearly through accidental irregularities, 

 but that the law of the inequality varies greatly from year to year. — In 

 Chemistry we have various communications, rather on details than on 

 principles. Mr. Schuster's paper on the spectrum of nitrogen points out 

 a cause of occasional errors in spectroscopic inferences. A late commu- 

 nication from Sir B. C. Brodie appears to prove that ozone is an allo- 

 tropic form of oxygen in which three volumes of oxygen are condensed 



