20 EEPOET OF THE SECEETART. 



values of tlie diurnal inequality of the declination were deduced for 

 every hour (mean local time) and also compared with similar values 

 for the same period observed at Greenwich. This inequality at these 

 two stations presents, in general, the same characteristic features, 

 namely: the principal deflection of the needle to the west shortly after 

 noon, and the opposite eastern deflection about midnight. The ex- 

 treme westerly position at Van Rensselaer Harbor is attained at noon; 

 the easterly extreme is reached at 2 a. m. A small disturbance is 

 noted at the hours of 4 and 5 p. m. While the diurnal variation 

 agrees with that observed at Lake Athabasca, Fort Simpson, Sitka, 

 Toronto, &c. , it shows no trace of that marked deviation exhibited at 

 Reikiavik, in Iceland, and Fort Confidence. The results were further 

 compared with similar ones at Whalefish islands and Port Bowen. 

 The range of the mean diurnal inequality was 1° T'. 



The mean disturbance of the declination for each hour was found 

 greater than at Lake Athabasca and Fort Simpson. The disturbing 

 force is least from 10 a. m. to 7 p. m., and greatest and equally 

 regular from 8 p. m. to 8 or 9 a. m. At noon, as at Lake Atha- 

 basca, Toronto, and Sitka, an increase in the mean disturbance is 

 noticed. The minimum disturbance takes place at 5 p. m. The 

 mean monthly disturbance was greatest in February. The recog- 

 nition and separation of the disturbed observations was effected by 

 application of a method proposed by Professor Peirce, according to 

 which, one in every eighteen of the whole number was found disturbed^ 

 that is, differing more than 1^ 38' from the mean, while at Toronto 

 the disturbance was one in every seventeen. The aurora horealis was 

 carefully noted, and in no case did the needle show any special 

 deviation during its occurrence — a remarkable circumstance, in con- 

 sideration of the fact of the great disturbances noted during the 

 appearance of this phenomenon farther south. 



The term-day observations, made once in each month, from January 

 to July, 1854, were exhibited graphically, and compared with corre- 

 sponding observations at Washington and Greenwich. The observa- 

 tions are marked by the absence of any considerable disturbance, 

 and by the small diurnal range at the time of the equinox. The 

 absolute declination was determined on three days in June, 1854, 

 and found to be 108° 12' west. The magnetic inclination was obtained 

 at ten stations, which gave for Van Rensselaer's Harbor a dip of 

 84° 45'. 8 from observations between January, 1854, and May, 1855, 



