OF THE EXPEDITION. XX111 



discussed by Professors Benjamin Peirce, Joseph Levering, William C. and Gr. P. Bond, and 

 Lieut. Chas. H. Davis, U. S. N. a committee appointed by the president of the Academy of 

 Arts and Sciences; and, finally, the two committees met at Philadelphia in joint conference. 

 There being differences of opinion respecting those portions embraced within the [ ], it was 

 mutually agreed to omit them. The remaining portions being fully approved, were recom- 

 mended for the adoption of the honorable Secretary of the Navy; the committee also submitting 

 to him that three assistants should be allowed, instead of only one, as I had proposed. 



Approved by the department, and the necessary authority granted me to proceed in the 

 premises, Messrs. Pistor & Martins were at once requested to construct a meridian circle, my 

 only stipulations being, that the divided limb should be full thirty-six inches in diameter and 

 read by four micrometers to spaces at least as minute as 1", and that the telescope should have 

 a clear aperture of fifty-one lines. It was suggested, among many other points, that the tube 

 of the telescope should be quite as conical as that of the transit instrument at the Washington 

 observatory ; that there should be two systems of micrometer wires at its eye-end susceptible 

 of illumination on a dark field, as well as in the ordinary mode of being made visible by light- 

 ing the field through the transverse axis ; that the level should be made with a reserve chamber ; 

 and that the counterpoises should be so arranged that it would not be necessary to remove them 

 for reversal of the instrument ; but the weight of metal in the circles, the number of radii, length 

 of transverse axis, diameter of pivots, and all other details not specified, were left entirely to 

 their discretion and judgment. Indeed, except as to the two given dimensions, I desired them 

 to regard all the remainder of the instructions as indications of my wishes, which were not to be 

 considered as positive directions when they conflicted with any better known mode of construc- 

 tion. Subsequently, Mr. Schumacher kindly consented to counsel the artists for me, and they 

 referred to him whenever they sought authority, instead of waiting until letters could cross the 

 ocean, and a reply reach Central Europe. 



The order was received on the 26th October, during the temporary absence of Mr. Martins, 

 and on the 31st July fr-ilowing a letter was written to me by our accomplished secretary of lega- 

 tion, Theo. S. Fay, Esq., saying : "I have one moment, before we close our despatches, to ac- 

 knowledge your kind favor of the 16th ultimo, and to communicate the excellent news that your 

 beautiful instrument is entirely completed, and stands in a perfection unrivalled. I have just 

 been to see it; and though my opinion of the manner in which Pistor & Martins have executed 

 their task would not be worth much in a scientific point of view, it will go better when backed 

 by that of Encke, who has fallen in love with it, after a careful examination. I must say, if you 

 discover a new sphere in the heavens, the least you can do is to call it 'Pistor & Martins! "for 

 their punctuality has equalled their skill." I will leave the distinguished Berlin astronomer 

 to express his own opinion of the instrument in another place, (Introduction to Vol. 4), but 

 feel it due to these skilled and faithful artists to add here, that the circle ordered differed so 

 greatly in construction and cost from the one they had sent me an estimate for, it was necessary 

 to write for additional authority subsequent to the letter of September 26, and this authority 

 did not reach them until January. Yet, so determined were they to fulfil their pledge, and 

 not disappoint me, that workmen were employed to relieve each other, and, as promised, the 

 instrument progressed to completion within the nine months day and night ! Would that all 

 were alike punctual ! 



It will have been perceived that the contemplated form to place a prism at the centre of the 

 transverse axis, so as to throw the pencil of rays from the object-glass through one of the pivots 

 was departed from in the order for the circle. This was out of deference to the opinions of 

 American astronomers, who thought it would be a great risk to be wholly dependent on an 

 instrument of untried construction, in a country where it would be difficult, if not impossible, 

 to remedy defects. Eminent artists in Europe thought it would possess extraordinary advan- 

 tages, and the astronomers who wrote to me considered it certainly much more efficient for a single 

 observer than the ordinary one so much so, that, were they ordering for themselves, they 



