DESCRIPTION OF THE RECONNAISSANCE. 



The comniencoiiu'iil liMvinj;- been in tlio early pjvrt of June and the termination in the hitter 

 part of November, nearly six months were oeenpied in prcb'minary and actual lield labor, which 

 proved a propitious season, considerinj;' the varied ehanses of temperature in sonic of the more 

 northerly sections near to, an«l north of, the latitude of White Pine. In this vicinity the winters 

 are very severe, especially in localities having' a high altitude, while the summers are delifjhtful, 

 e.\cei>t at some few ])laces at which fogs and winds ])revail. 



The melting of the snows in spring furnishes water in abundance for the wants of vegetation, 

 and the bunch-grass, so common among the hills, is in its best condition. Our return-trip brought 

 us again to this region prior to the harsh snows and severe temperatures of the coming winter ; 

 while the time at which tlie immediate desert of the ("ohnado was reached (in October) was too 

 late for the glaring and continuous heat of the midsummer days. 



The greater actual acciuacy of prominent points of the survey is in the area north of White 

 I'ine, since the four positions at which longitude by tclegra|)h was obtained form the ground- 

 work, while the lines that act as bases, going toward the Colorado, are nearly north and south, 

 giving fewer chances for a great error in longitude, where alone errors of any cousiderable mag- 

 nitude arise. 



The use of the little Held tlieodolite, constructed especially for reconnaissance-work, has proven 

 to be such a great improvement that very little chairge between the positions, as obtained from 

 the results of the astronomical work and the meanders, was necessary to be made. The porta- 

 bility of the instrument ami the accuracy of its readings recommeml it at once as an almost indis. 

 pensable article for exploring parties, and to their use the accuracy of the i)re.sent reconnaissance 

 has been greatly due. 



The daily march varied Irom ten to thirty miles; the survey parties, in extreme cases, have 

 been managed independently of the main party, falling back upon it for supplies. 



The traveled roads or trails, carefully meandered and measured by odometers, form the base- 

 line for the triangulated points, the stations never exceeding two or two and a half miles apart, 

 and such distances only occurring in valleys where the road was nearly straigiit. 



The magnetic bearings were corrected by tiiuling the variation of the needle at every camp. 



The heights of the |iromineut peaks ha\e generally been determined l)y using angles of eleva- 

 tion taken from |)oints on the base-line, the elevations of which have been determined from baro- 

 metric work. This has been tnodified at points where peaks could be ascended, and here barometric 

 readings have been used, and advantage of such occasions has been taken to triangulate to distant 

 peaks that, at times, could be distinctly deliued against the horizon at a distance of one humlrcd 

 ami tifty miles. Stone monuments have been erected at these stations as reference-jioints for the 

 futnie. 



The necessities of the march and the desire to travers(! as large an area as possil)lc have 

 caused in some cases a deliciency of topograi)hical detail, while, on the other hand, the general 

 features as regards positions of prominent points, and practical information, are of a sufficiently 

 accurate nature to answer all present wants. 



PERSONNEL. 



First Lieut. George M. Wheeler, Corps of Engineers, in charge ; First Lieut. D. W. Lock- 

 wood, Corps of Engineers, executive oflicer ami astronomical assistant; 1'. W. llamel, principal 



