OF THE UNITED STATES. 24,7 



4. Four double repoalin'>; reflecting; circles, often inches 

 diameter, with stands and artiticial mercury horizons, and 

 spirit levels lor measuring small angles of elevation, made 

 by the same. 



5. Two reflecting circles exactly like the former, without 

 stanilsor levels, hy the same. 



6. Two artificial Iiorizons of mercury, with a glass cover. 



7. Two artilicial horizons, of dark plane glasses, of eight 

 inches diameter, with ground spirit levels. 



8. Two common surveying theodolites, of nine inches 

 diameter. 



y. Two compasses, with needles one foot long, with cen- 

 tre work and spirit levels, made by Thomas Jones. 



10. Two alhidadcs for plane tables, with transit telescopes, 

 made by Thomas Jones. 



11. Two plane tal)lc's, suited to these instruments. 



12. Two sets of apparatus lbi- measuring base lines by a 

 peculiar arrangement : each set consisting of the following 

 parts, viz. four bars of iron, intended to be made the length 

 of two metres ; various screw works and a numl)er of roll- 

 ers for the motion of these bars, and of tlic boxes intended to 

 receive them ; a sector with a spirit level ; a directing teles- 

 cope ; four thermometers ; and three stands, with motion 

 works, and microscopes with two different loci. Made by 

 Mr. Trougliton. 



13. One standard Rnslish brass scale, of eighty-two inches 

 in length, divided on silver into tenths of inches, with a mi- 

 croscope, and an arrangement for the comparison and con- 

 struction of other scales. Made by Mr. Trougliton. 



14. One iron toise, standarded by Lenoir in Paris, and 

 compared with the toise of Peru at the observatory, by- 

 Messrs. Arra2;o and Houvard. 



l.T. One brass metre, standarded by Lenoir, and compared 

 with the iron metre at the observatory of Paris, by the same 

 gentlemen. 



ift. A certificate of these two comparisons, signed and 

 sealed by these gentlemen. 



