Magnetic Influence of Solar Light. 24*5 



periments requiring delicate apparatus and minute observa- 

 tion are attended in this country by peculiar difficulties- 

 difficulties too that increase in rapidly accelerated pro- 

 portions as we recede from large towns or stations. The 

 mechanical resources necessary for the construction of 

 scientific apparatus are peculiarly difficult to command, and 

 in many instances, it is necessary to procure their most 

 essential parts from great distances. Thus I have been 

 unable to obtain a common prism from any place nearer 

 than Calcutta, a distance of upwards of a thousand miles 

 from the spot where these experiments have been made, and 

 similarly with other parts of the apparatus I have employ- 

 ed. Still if difficulties such as these were to be allowed to 

 deter us wholly from scientific research, but very little 

 would be done in this country, since they meet us at every 

 step — they may however be pleaded as a reason, why that 

 minuteness of observation, confessedly so desirable, may 

 not at all times distinguish our experiments, and will excuse 

 the expedients to which we are occasionally obliged to have 

 recourse to work out our views. Another disadvantage of 

 localities so remote as that where the experiments to be 

 subsequently detailed, were made, is the impossibility of 

 obtaining books for the purposes of consultation. Of the 

 various researches on the subject of solar magnetism to 

 which allusion has been made, I have been able to obtain 

 only the merest abstracts of the original memoirs, and have 

 consequently been compelled to follow throughout my own 

 experiments, that course which appeared to me best. The 

 results I have obtained, I therefore give in the fullest detail, 

 so that if any sources of error exist in them, they may 

 readily be detected and allowed for. The experiments will 

 be divided into the three following sections : — 



Section I. — On the magnetic action of undecomposed light. 



Section II. — On the magnetic action of the rays of the 

 prismatic spectrum. 



2 K 



