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Show 344 REPORT OF THE CHIEF OF ENGINEERS. could be accurately determined, and found to be as follows: At Stone's Ferry, 17 feet, high-water mark of 1871; south end of Cotton wood 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 Ehrenberg, 8 feet; Fort Yuraa, 10.19 feet, high-water mark of 1862; Fort Yunia, 9.16 feet, high-water mark of 1873; Fort Yunia, 6.07 feet, high-water mark of 1875. When the observations were taken at Camp Mohave the river had nearly reached its .lowest 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 s«;ut 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 Yunia our barometers were compared with that of the signal-oflice, and a series of hourly readings were taken, which was also doiie at other camps where we remained two or three days. Cistern-barometer readings were also taken on monn tain-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 teniporary 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 aren whose climate was nearly the same, while at places west of the Cajon and San (iorgonia 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 every case the coincidence was as close as could be expected. The computed altitude of Camp Mohave, 7;V».d 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\ were separately computed. The wauderiug from the mean was next obtained and the observations thrown out which showed au abnormal variation, and a new mean obtained. This altitude was then used to com- Cute the altitudes of camps already referred to Los Angeles, giving results differing ut little from those previously deduced. GEOLOGY, MIXKKALO<;V, 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 numerous 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, aud the absorption of water. He also obtained hundreds of new words from different Iudiau tribes, and conducted tho experiments on evaluation. It would be desirable to have his rc]H»rt accompany mine. On the second trip collections of the llora and fauna of the country traversed were made, specimens of soil from various localities collected, aud Iwttles of water brought iu from all thermal aud mineral springs within our reach. CLIMATIC 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 to tho 1st of October panting humanity linds no relief from the heat. As soon as the siiu appears above the horizon its heat is felt, and this continues to increase until a maximum is reached about '.i o'clock in the afternoon, after which the temperature falls slowly, and oftentimes very slowly, until sunrise. During the hottest part of the day |