544 GEOLOGY OF THE 15 LACK JllLLS. 



Believing that after our arrival in the country to be surveyed, wagons 

 would have to be dispensed with, and that we should have to take to the 

 saddle, I did not think it advisable to take more than two large chronom- 

 eters ; and my experience in the field during the past summer showed that 

 I was correct ; for had I taken more, some of them would have had to be 

 turned into other hands and would have been of no use to me, and most 

 likely would have been ruined. As it was, the two chronometers received 

 from the Messrs. Negus did not pass out of my hands from the time of 

 leaving Cheyenne, in May, until our return there in October. 



From Stackpole & Brother the department authorized the purchase of 

 one transit theodolite, one astronomical and one lunar sextant, and two 

 artificial horizons. These instruments were all new and of the very best 

 workmanship, as are all instruments which come from the hands of these 

 celebrated makers. For the rough country in which we had to work, the 

 theodolite was not well suited from its great weight, but a lighter one could 

 not be procured. 



2. Longitudes. 



Upon my arrival at Cheyenne I learned something definite about the 

 character of the Black Hills country, and it at once became evident that 

 the only thing to be done, so far as longitudes were concerned, was to 

 measure " meridian distances" from point to point, obtaining the chronom- 

 eter errors and rates as often as our delays would permit, until we should 

 arrive at some prominent point in the Hills, where our theodolite could be 

 brought into use. From the nature of the country we were to visit, it was 

 simply out of the question to start from Cheyenne or Fort Laramie with 

 the errors and rates, and then trusting to chance of obtaining them again 

 on our return, and deducing therefrom the longitudes. This would have 

 been the proper method to have pursued had we been going to a country 

 easy of access and travel, but not in a rugged country like that which we 

 visited ; and my only course was to follow the more complicated method 

 of " meridian distances." 



It was my intention to have combined my chronometric longitudes 

 with those deduced from occultiitious, or in case of accident to the chro- 



