LIST OF APPARATUS RELATING TO HEAT, LIGHT, ELECTRICITY, 

 MAGNETISM, AND SOUND, AVAILABLE FOR SCIENTIFIC RE- 

 SEARCHES INVOLVING ACCURATE MEASUREMENTS.* 



Professors Wolcott Gibes, Edwaed C. Pickering, and John 

 Teowbeedge, of Harvard University, have lately corresponded with 

 the leading institutions of learning, and obtained consent for the use 

 of the below-mentioned instruments for purposes of research by prop- 

 erly-qualified persons. 



UiTiTED States Coast and Geodetic Suevey Office, WASHma- 



TON, D. C. 



The use of this apixiratus may be had at the office, under appropriate 

 reguhitions. Applications must be made to Capt. C. P. Patteeson, 

 Superintendent United States Coast Survey. 



1. €omj)arators of length : 



a. Saxton's pyrometer, or mirror comparator, for end measures. 

 h. Eepsold's contact-lever comparator, for end measures. 



c. Saxton's tracing and comparing machine, for line measures. 



d. Hilgard's comparator, for line and end measures for any length 

 between three and forty inches. 



€. Eutherfurd's micrometer, with two screws at right angles, and circle 

 of i)osition for mea.suring stellar and solar photographs. 



2. Standards of length : 



a. Standard iron meter of originol committee for establishing metric 

 system (end measure). 



h. Standard British yard (line measure). 

 Standard British yard (end measure). 



Eighty-four-inch scale, di\ided to tenths of inches, made by Troughton 

 and comi)ared throughout by Hassler. 



c. Decimetie divided into centimetres and millimetres, compared with 

 the original standard metre. 



d. Copy of toise, accurately compared. 



3. Apj)aratm for ^ceUjliing. — Balances of precision for maximum charges 

 of 100, 10, and 1 kilogrammes, and 100 and 1 grammes. 



4. Standard tceights. — Standard troy and avoirdupois pounds; kilo- 

 gramme in i)latinum and in brass accurately compared. 



* From the Scientific American Supplement for August, 1879, 



429 



