6 



EEMAEKS ON METEOROLOGY AND BAROMETRIC RESULTS. 



between Cape Mendocino and the mouth of Columbia river, within the accumulative influence 

 of the return trade winds of the Pacific. 



The mean of seven observations with air temperature of 58°, taken by Lieut. Michler at 

 New Town, San Diego harbor, to which the same corrections for the various elements of error 

 as used in the above work, were applied, gave for the height of mean tide 30.018. From the 

 above results we have tJ^e following table, uncorrected for gravity, and contrasted with a portion 

 of Schouw's table f r the North Atlantic ocean. 



FROM FORT YUMA TO FORT FILLMORE. 



To obtain the corrections for the temperature of the mercury above 100°, the formula given 

 in the Smithsonian tables, prepared by Professor G-uyot, was used. The correction for constant 

 error was obtained by mutual comparisons of barometers 392 and Y90, (Green's cis.,) and with 

 the Smithsonian standard at G-reen's instrument depot, New York city. Frequent observa- 

 tions were taken to determine the horary correction between Fort Yuma and Fort Fillmore. 

 The corrections are given in Table No. 3, and constructed in Plate \, figure 4. A peculiarity 

 was observed in this phenomenon, which will be adverted to in the sequel. 



To determine the measure for abnormal oscillations of the barometer, a sufficient number of 

 observations along the line of survey or in the contiguous regions could not be obtained with 

 which to compare. The observations at San Diego, however, were compared with those of 

 Lieut. Michler, at Fort Yuma, during the months of December, 1854, January, and part of 

 February, and, with those of our own, in June, 1855, and gave very satisfactory results, and from 

 this comparison a scale of corrections was obtained for that place. By reference to the diagrams 

 it will be seen that the fluctuation of the atmosphere occurred very nearly simultaneously at 

 those places, and, consequently, an accurate measure for the abnormal error was probably 

 obtained. For the months of December, January, and part of February, the average amount 

 of correction was found to be «w'?i?<s0.180, and for the middle of the monthof JunepZwsO 100. To the 

 observations of Lieut. Michler the former correction was applied, and gave for the height of his 

 astronomical station No. 1, opposite Fort Yuma, 35 feet above the surface of the river 310.8 

 feet, and for the level of the water 275.8 feet above mean tide at San Diego. At Camp 60, 

 (Gila river,) about 7 miles above the junction of the Colorado and Gila rivers and about 20 feet 

 above the water, 52 observations were taken, to which were applied the latter correction for 

 abnormal error, and gave for the height of the Gila at that point 296.6 feet above mean tide at 

 San Diego. Four observations at Ankrim's ferry, about one and a half miles below Lieut. 



