206 Application of the Galvanic Circuit 



The whole of this has been sent to Great Britain, with the ex- 

 ception of 15 piculs to Mauritius, 470*68 to the continent of Eu- 

 rope and 922 to the United States. 



About 270,000 taban trees have probably been felled during 

 the 3£ years the trade has existed, and the value of each tree has 

 thus, on an average, been about a dollar. 



The price of taban in Singapore gradually rose from eight to 

 twenty-four dollars per picul, but last month it began to fall and 

 is now about thirteen dollars. 



In our next, [Jour. Indian Archipelago,] we shall give some 

 more exact details, and notice the mixtures of gutta percha, jelo- 

 tong, gegrek, litchu and other inferior guttas, the products of dif- 

 ferent trees, which are sometimes used to adulterate the taban. 

 A large lump was brought to us a few days ago consisting of 



gutta percha and gegrek, enveloped in a coating of taban about 



a third of an inch in thickness. 



Art. XIX. — Application of the Galvanic Circuit to an Astro- 

 nomical Clock and Telegraph Register in determining local 

 f differences of longitude, and in astronomical observations gen- 

 erally, in a communication by Sears C. Walker, Assistant 



U. S. C. S., addressed to Prof. A. D. Bache, LL.D., Supt. U. S. 

 Coast Survey : — forming a Report to the Treasury Depart- 

 ment, by Prof. Bache, and presented to Congress with a letter 

 by the Secretary of the Treasury.* 



I beg to call your attention to the importance of the use o( an 

 «lectro-magnetic circuit and an astronomical clock in connexion 

 with Morse's telegraph register for the operations of the coast 

 survey, and the general purposes of practical astronomy. Your 

 \houghts having been first turned to the subject of the use of 

 Morse's electro-magnetic telegraph in the longitude operations of 

 the coast survey, in December, 1844, special instructions were is- 

 sued to me in the autumn of 1845. Under these and subsequent 

 instructions, the operations of 1846, '47 and '48, entrusted to my 

 care, have, until near the close of the latter year, been conducted 

 without the use of the automatic clock register. 



The importance of the latter instrument induced you to direct 

 the necessary researches to be instituted, for the purpose of intro- 

 ducing it into use in the coast survey service. Several methods 

 have been suggested by eminent mechanicians and electro-mag- 

 netists. That of Mr. Wheatstone is briefly alluded to in the pro- 

 ceedings of the Royal Astronomical Society, for Nov. 19th, 1841. 



* Exec. Doc. No. 21, House of Representatives, 30th Congress, 2d Session 



