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Show 124 could be accurately determined, and found to he as follows: At Stone's Ferry, 17feet, high- water mark of 1871; south end of Cottonwood Island, 14 feet; Camp Mohave, 8 feet, high- water mark of 1872; proposed railroad crossing, north of the Needles, 20 feet; Needles, 18 feet; Camp 40,15 feet; opposite Ehrmberg, 8 feet; Fort Yuma, 10.19 feet, high- water mark of 1862; Fort Yuma, 9.16 feet, high- water mark ol 1873; Fort Yuma, 6.07 feet, high- water m*. rk of 1* 75. When the observations were taken at Camp Mohave the river had nearly reached its owest stage, although it usually continues to fall slowly until after Christmas. METEOROLOGY. As previously mentioned, one enlisted man, Private Charles Lengert, Company G, Twelfth Infantry, was sent by stage to Camp Mohave to take barometric and psychro-metric observations during the summer. This duty he executed faithfully and well, for which he deserves a great deal of credit. Observations were taken in camp at regular hours, and comparisons of instruments and observers were frequently had. At Fort Yuma our barometers were compared with that of the signal- office, and a series of hourly readings were taken, which was also done at other camps where we remained two or three days. Cistern- barometer readings were also taken on mountain- peaks and on the principal divides. In this way a great number of observations were obtained from which to calculate the altitudes of the different camps. The observations taken on the first trip were reduced and altitudes computed in the temporary office at Los Angeles during the winter months. Those taken on the last trip have not yet been computed. The method of computation used differs from that used in the office at Washington for this reason: It was found that the horary curves at Los Angeles and Camp Mohave differ considerably; that of the latter place being much sharper and having a wider range. This was to be expected, since the climate differs so greatly from that at the former place. For this reason the proper correction was applied to the readings before computations were made. The horary correction for Camp Mohave was used for all places included within the desert area whose climate was nearly the same, while at places west of the Cajon and San Gorgonia Passes the horary correction for Los Angeles was used. The daily means of synchronous observations were computed separately, after which the results were examined, and those which were unmistakably bad were thrown out. The mean of the remaining ones were then taken as the true altitudes. To check the results the altitudes of several camps were computed with both Los Angeles and Camp Mohave as reference- station, and in eveiy case the coincidence was as close as could be expected. The computed altitude of Camp Mohave, 755.8 feet, I was disposed to consider too great, as it exceeded by 100 feet all previously determined or estimated altitudes. Hence,* every precaution was taken to determine this accurately. The daily means of the synchronous readings for over 70 days j were separately computed. The wandering from the mean was next obtained and the observations thrown out which showed an abnormal variation, and a new mean obtained. This altitude was then used to compute the altitudes of camps already referred to Los Angeles, giving results differing but little from those previously deduced. GEOLOGY, MINERALOGY, AND NATURAL HISTORY. Dr. Oscar Loew, chemist and geologist, had charge of these branches during the first trip, and was indefatigable in the prosecution of his duties. He took copious notes and sketches of the geological formations, collected numerons mineralogical specimens, visited all the mines in the vicinity of our route, and obtained many specimens of plants, insects, and reptiles. Mineral water was taken at several points, and specimens of soils and saline deposits were obtained for analysis. He also made some original investigations on the influence of extreme heat on the rapidity of the pulse, inhalation and exhalation, and the absorption of witter. He also obtained hundreds of new words from different Indian tribes, and conducted the experiments on evaporation. It would be desirable to have his report accompany mine. On the second trip collections of the flora and fauna of the country traversed were made, specimens of soil from various localities collected, and bottles of water brought in from all thermal and mineral springs within our reach. CLIMATE. The climate in the Colorado Valley during the hot months is not one which a sane person would select in which to spend the summer. From the middle of June totbe 1st of October panting humanity finds no relief from the heat. As soon as the sun appears above the horizon its heat is felt, and this continues to increase until a maximum is reached about '•& o'clock in the afternoon, after which the temperature falls slowly, and oftentimes very slowly, until bunrise. During the hottest part of the day |