10 REPORT — 1842. 



These, and his observations of the magnetic terms with their graphical pro- 

 jections, continue to be regularly published by him in the Bulletins of the 

 Royal Academy of Brussels. 



Dr. Lloyd, Dr. Laraont, and Messrs. Lovering and Bond have respectively 

 furnished descriptions of the magnetic observatories under their direction at 

 Dublin, Munich, and at Harvard University, Cambridge, N. S. In the last- 

 mentioned of these works (published in the Memoirs of the American Acade- 

 my of Boston,) are also printed the term observations made in 1840 and the 

 commencement of 1841 at that Institution, projected, and in the case of the 

 term of Oct. 21, 1840, compared with the corresponding observations at 

 Toronto (as regards the declination), and exhibiting (conformably to what has 

 been found to obtain in stations not more distant from each other in Europe) 

 a close and minute agreement in the march of the deviations, which on that 

 occasion was very irregular. 



Dr. Lamont's observations are characterized by the use of very small 

 needles. Some anomalies appear to have been produced in their readings by 

 circulating currents of air arising from inequality of temperature in their 

 glass inclosures ; but these he has succeeded in great measure in destroying. 

 Indeed there seems no good reason why such needles should not be sus- 

 pended in vacuo. Assuredly if very small needles could be used in place of 

 large ones, (for those observations, that is to say, which do not depend on 

 observed times of vibration, for to such they are quite inappropriate,) not only 

 would the costliness of apparatus be much diminished, and its portability in- 

 creased, but the temperature corrections would become more certain, by rea- 

 son of the rapid distribution of heat through the whole extent of the needle, 

 (neither would there probably be found much difficulty in keeping such 

 needles constantly up to a definite state as to magnetic saturation) not to re- 

 fer again to what has been already said of their applicability to a closer ana- 

 lysis of the shocks producing irregular disturbances. 



Dr. Lloyd's paper may be advantageously referred to for a full account of 

 the construction, adjustments and mathematical theory of all the magnetic in- 

 struments employed, and in this respect must be considered as a very useful 

 and valuable contribution to the cause in hand. 



Col. Sabine has reduced and discussed during the past year the observa- 

 tions of Capt. Belcher on the west coast of America and at Otaheite in the 

 second series of his " Contributions to Terrestrial Magnetism" published in the 

 Phil. Trans., 1841, and in his third series of such contributions has passed 

 under examination the sea observations of intensity made onboard the Erebus 

 and Terror in the voyage from England to Kerguelen's Land. 



Professor Loomis's observations of intensity and dip in several stations in 

 the United States, made in the years 1838, 1839, 1840, have also appeared in 

 the year elapsed. 



The subject of the mutual action of permanent magnets, with a view to 

 their best relative position in an observatory, has been resumed by Dr. Lloyd 

 in a supplement to his former paper on that subject published by the Royal 

 Irish Academy. Choosing among the incompatible conditions which a total 

 destruction of the mutual actions of three magnets would require those of 

 most importance to satisfy, he has been enabled to propose several arrange- 

 ments adapted to specific purposes, which accomplish their object with great 

 simplicity and convenience. 



A considerable extent of correspondence has taken place on the important 

 subjects of the best formula to be used and method to be adopted for deter- 

 mining the absolute intensity of a magnet by deflection observations, Mr. 



