ORIGIN AND OPERATIONS 



>r be Ml" divided by the square root of fil) = 0".13 : ami. lastly, that the attainment of such 

 A solution, if accordant in imiiviiliml r< .suits. would, lit all events, place tin- parallax beyond 

 cavil.it did appear to me an o 1 effort t. ehi0V8 for onr ooubrj and its 



navy. I am convinced such a result ran lx> attained in a single interior conjunction ; and that I 

 can accomplish it. if a suitable instrument be -riven me. and as close an observer have charge of 

 the northern circle, I am willing to ha/ard whatever of reputation as an observer may have 

 been award' If the period of simultaneous observations is to be extended to another 



conjunction, the probable error will, of course, fall within 0".l, and such continuation of the 

 erica appears to IH> t!. -fall who have communicated with me on the subject. 



.tcrtaining these opinions, the letter of July 'J~> was written to Dr. Gerling, and in a 

 short jHTiod the correctness of my judgment was confirmed by Messrs. Bache, Walker, and 

 Loomia, all gentlemen thoroughly versed in the theory as well as in the manipulation of instru- 

 ments. Thi was sutlicient incitement to leave no effort untried to secure the honor of the 

 observations for American science. Dr. Gerling's letter of September positively decided mo ; 

 and should he procure recommendations of the Expedition from German astronomers, as therein 

 promised. I shall Ivave nothing undone to the fulfilment of my portion of the engagement. 



" Between the date of my letter and the receipt of that last alluded to, the subjects of parallax 

 and climate of Chile wire made matters of especial examination. It was not until then that I 

 became acquainted with the close agreement of the results of Encke and Ferrer upon a discus- 

 sion of all the observations of 17fi9, and will candidly confess that this, together with the unfa- 

 vorable accounts gathered of ('hiloc, if not quite so dampening to my zeal as is the (reputed) 

 climate of the Mat ion selected to the skins of Chilotes, was yet very far from a character to 

 alfor-1 encouragement. But, as I hav u tiered minor obstacles to deter me from the pros- 



in of a worthy task, and the following good reasons exist why the work should go onward, 

 I am prepared to make every promise good to its fullest extent. 



"First. The solar parallax rests on the isolated deductions from the transit of Venus, as 

 observed in 17C9, a part of which observations arc, demonstrably, forgeries, a part supposed to 

 bave been 'coaxed,' (as generally termed 'cooked,') and another part, viz: at Santa Ana, in 

 it'ornia, made or manufactured by one scarcely rational. Those of Mars at opposition in the 

 last century, which are referred to by Encke in his Venus durcJiyang von 1769, and by Dr. 

 ling in his letter of April 17, 1 have not been able to find here, and, apparently, there is 

 but one other occasion when this method has been made use of. Prof. Henderson made a com- 

 parison of the Cape of Good Hope observations of Mars, at opposition with nearly simultaneous 

 ones at Cambridge, (England.) Greenwich, Edinburg, and Altoiia; and though those made at 

 the first named northern observatory, combined with the ('ape measures, gave a parallax agree- 

 ing very well with the received amount, the comparison with the others afforded a result 

 ig '.". These two modes, and the only ones tried, do not rest on a sufficient number of 

 obo- dvanced state of astronomy demands their confirmation, and the removal 



of whatever of doubt may hang over the solution of tin- problem. 



"Second. The method proposed by Dr. Gerling is the only one remaining untried by which 

 we can ever arrive at a know . :ilax; and as this element may be positively ascer- 



tained during two inferior conjunctions within the limits "of 0".09, its investigation, in the 

 manner matured by him, is not only desirable, but its accomplishment will Ix- alike honorable 

 to the nation that directs and the astronomer who accomplishes it. 



"Third. Considering the second reason incontrovertible, the magnitude of the object involved 

 renders it well worthy tin- patronage of the government. Now, as wo can hope to enlist our 

 countrymen in scientific enterprises only by their so frequent recurrence as compels belief in 

 their national utility, and as many years have elapsed since voluntary part has been taken in 

 any work t thin character. i ,-;,/. the Kxploring Expedition, ls:!.1i. unless we wish all interest in 

 like pursuits to be lost, it is time rulers were again called on to act, and the present occasion, 

 ip. emphatically addresses itself to us there being high honors attainable at little cost. 



