72 AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 



results of different trials with different observers for personal. equation, and the 

 comparison of the ratio of the observing chronometers with the changes of tem- 

 perature. 



From the observed changes of rate of all the chronometers compared with the 

 chano-es of temperature, corrections were obtained by the method of least squares, 

 and applied to the rate of each instrument so as to reduce them to a mean tem- 

 perature rate. 



The rates of the chronometers when stationary and travelling were deduced, 

 the first by observations between the times of arrival and departure from the two 

 stations, the second by considering the trips to and from Savannah and to and 

 from Fernandina, and assuming equal travelling rates out and back. To these 

 rates a correction was applied by the method of least squares, which, as was ex- 

 pected, turned out to be quite small. In determining this correction the hypothesis 

 of equality of rates was dispensed with. 



The two sets of chronometers each containing five instruments differing by 



nearly three-fourths of a second in the result for longitude, and consistently in the 



different trips, it was determined to transport them together so that they might be 



exposed to the same circumstances. This was done without any change of the 



results. 

 In deducing the final longitude weights were allowed according to the inverse 



ratios of the squares of the chronometer errors and also according to the duration 

 of the trips. 



The discussion gives 1 min. 29.76 for the difference of longitude of the stations 

 "at Savannah and at Fernandina, with a probable error of 0.06. 



ON THE WINDS OF THE WESTEEN COAST OF THE UNITED STATE'S, FROM OBSERVATIONS 

 IN CONNECTION WITH THE COAST SURVEY. BT A. D. BACHE, SUPERINTENDENT. 



{^Abstract for the Canadian Journal} communicated hy the Author.) 



The observations were made in connection with those of the tides in 1855 under 

 supervision of Lieut., now Professor Trowbridge. 



They are reduced by the methods stated in the paper on the winds of Cat Island 

 in the Gulf of Mexico, and read before the Association in 1851. 



The diagrams representing the winds for each month, for the half year and year, 

 are plotted upon the compass rose, and show the quantities of vind. Others 

 representing the hourly observations made each week are upon the ordinary rect- 

 angular system. They show better than any verbal descriptions, the whole of the 

 phenomena of the winds at San Diego, San Francisco, and Astoria, during the 

 year 1855. 



The following simple generalizations are deduced : 



1. The great prevalence of westerly winds representing a flow of air at the 

 surface from the ocean in upon the land. 



2. The general absence of easterly winds showing the absence of a return cur- 

 rent at the surface. The proportion of westerly to easterly winds is as 8 to 1. 



3. The increase of westerly winds in the summer, and their decrease in the 

 winter. 



4. When easterly winds blow at all, it is as a rule during the winter. 



5. The N., 1^. E. and E, winds blow more frequently in the morning than in tlte 

 evening hours. 



