Latitude and Longitude of Yale College Observatory. 309 



dip in 1834 was at Cambridge 73° 33', being an increase since 

 1783 of 3° 52', or about four and a half minutes per year. It 

 may be considered as established, that the dip has increased in 

 this country since the earliest observations, but whether it is still 

 increasing at the present time seems more uncertain. The ob- 

 servations made at Albany and New York may excite a suspicion 

 that such is not the fact. It is hoped that so important a question 

 will not long remain doubtful. From this table of observations 

 I have laid down the lines of equal dip for every five degrees 

 upon the chart as well as I was able. These lines being deduced 

 from a small number of observations, can only be considered as 

 very rough approximations to the truth, and lay no claim to great 

 precision. The observation at Pittsburgh seems utterly irrecon- 

 cilable with the others. I can only explain the difference by 

 supposing it to be a wretched observation, or else that there was 

 a very remarkable local attraction, or finally, that there is some 

 typographical error. If we read 73° for 78° the observation will 

 agree tolerably well with the others. Few observers in the Uni- 

 ted States have instruments suitable for determining the dip ; yet 

 it is to be hoped that such as are thus furnished will make a 

 faithful use of them, so that we may soon be able to prepare a 

 much more accurate magnetic chart of the United States than 

 the one which is now presented to the public. 



Art. IV. — On the Latitude and Longitude of Yale College Ob- 

 servatory ; by Elias LooMis, Professor of Mathematics and 

 Natural Philosophy in Western Reserve College, Ohio. 



In the summer of 1835, being then at New Haven, I under- 

 took a series of observations for determining the latitude and 

 longitude of the College Observatory. The observations were 

 made under many disadvantages, with instruments poorly calcu- 

 lated for the purpose; yet as it is believed that the results are 

 more to be relied upon than those which have hitherto been 

 adopted, they are here summarily presented to the public. I know 

 of no attempt worth mentioning, which had ever been made to 

 determine the latitude or longitude of the College before the year 

 1811. President Day, at that time made a few observations for 



