x ;j ORIGIN AND OPERATIONS 



error be as 1" divided by tho square root of GO = 0".13; and, lastly, that the attainment of such 

 u solution, if accordant in individual results, would, at all events, place the parallax beyond 

 cavil, it did appear to nip an object worthy a great effort to achieve for our country and its 

 navy. I am convinced such a result can be attained in a single inferior conjunction ; and that I 

 can accomplish it, if a suitable instrument be given me, and as close an observer have charge of 

 tho northern circle, I am willing to hazard whatever of reputation as an observer may have 

 been awarded to me. 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 

 series appears to be the desire of all who have communicated with me on the subject. 



"Entertaining these opinions, the letter of July 25 was written to Dr. Gerling, and in a 

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

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

 ments. This was sufficient incitement to leave no effort untried to secure the honor of the 

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

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

 promised, I shall leave 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 were 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 1769, and will candidly confess that this, together with the unfa- 

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

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

 afford encouragement. But, as I have never suffered minor obstacles to deter me from the pros- 

 ecution 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 1769, a part of which observations are, demonstrably, forgeries, a part supposed to 

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

 California, 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 durchgang von 1769, and by Dr. 

 Gerling in his letter of April 17, I 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 Altona ; and though those made at 

 the first named northern observatory, combined with the Cape measures, gave a parallax agree- 

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

 exceeding 9". These two modes, and the only ones tried, do not rest on a sufficient number of 

 observations. The advanced state of astronomy demands their confirmation, and the removal 

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



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

 we can ever arrive at a knowledge of the parallax ; 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 be 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 the patronage of the government. Now, as we 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 of this character, (vide the Exploring Expedition, 1835), 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, 

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



