336 REPORT — 1851. 



The principal means which I have employed in its composition have been 

 references to my former Reports of a like kind ; examinations of the various 

 instruments, &c. spoken of; descriptions, &c. from my own portfolios ; the 

 Electro-meteorological Journal ; the tabulations and tracings of the magnetic 

 curves, &c., and the Kew Diary. 



The materials which I have used for supplying some omissions in our 

 Diary have been three manuscripts concerning tlie Meteorological Journal, 

 the Barometrograph, and the Hygrometers, drawn up by Mr. Welsh (our 

 observer). In making use of the Diary and all other documents, endeavours 

 have constantly been made to record shortly only such facts as may be, or 

 may become useful, and to do this in the words themselves of those docu- 

 ments wlienever a due regard to brevity permitted. 



The subjects are arranged under four heads : — 1st, tliose which relate to 

 the Building, Instruments, &c. ; 2ndly, those referable to the Observations ; 

 Srdly, experimental (and analogous) subjects ; and lastly, those which do 

 not properly belong to any of the former. 



I. THE BUILDING, INSTRUMENTS, &c. 



The edifice* has undergone no change of importance this year. The an- 

 nexation of three new corbels to the wall of the great mural quadrant, for 

 the support of a new Vertical-force Magnetograph, is probably a temporary 

 expedient. The custody of a large quantity of apparatus, consigned to our 

 care by the Royal Society, and of which a portion is highly valued, from the 

 circumstances of its having been- invented, or made, or even possessed by 

 such men as Boyle, Huygens, Newton, Cook, Cavendish, Coulomb, Le Roy, 

 Sabine, Kater, &c., renders a little reparation (of damage by dry rot) and 

 painting very desirable (a long time has elapsed since any interior painting 

 has been done) ; and it has frequently been thought advisable that the wall 

 of the great quadrant, which instrument has long since been dismantled, and 

 will never be again employed, should be converted into piers, pedestals, &c. 

 for the support of experimental instruments requiring scrupulous regard to 

 immutability of position and exemption from extraneous vibration f. 



In speaking of the Instruments, I refer principally to those which have 

 been more or less used in this year. 



Electrical Apparatus. 



The Principal Conductor, &c. on, and in, the Dome, and all the electrical 

 apparatus which has been employed for the observations of atmospheric 

 electricity, are in working order. The Rod, Lantern, &c., the Volta- 

 Electrometers, Henley -Electrometer, Discharger and Distinguisher, retain 

 the forms described at p. 123 {et seq.) of the Report for 1844', The Ob- 

 server's Clock and its scale remain as described at p. 178 of the Report for 

 1850. 



The Galvanometer of M. Goujon gives strong indications when connected 

 with the conductor, in times of violent rain, &c., but is not to be depended 

 upon as to measures. 



* Described at p. 120, Report for 1844. 



•f- Two of the magnetographs, although solidly, are inconveniently placed. The photo- 

 barometrograph requires a much better foundation than boards and joists can afford (as will 

 be seen) ; and for the due prosecution of projected observations of standard and other ba- 

 rometers, pendulums, &c., extremely solid bases cannot (obviously) be dispensed with. 



