260 REPORT—1858. 0 
General Summary, 
Imports. 
Z : Difference of Per 
No. of Register Tons Weight of ; 
Date. each: peso: ‘res ernel. tr Ma beer og 
Tonnage. 
1852 38,051 7,887,447 6,169,599 | —1,717,848 —21 
1853 | 42,876 8,943,106 7:525,063 — 1,418,043 —15 
1854 | 41,591 9,161,366 7,290,996 — 1,870,370 —20 
1855 | 40,980 8,951,239 6,254,259 | —2,696,980 | —30 
8 ee eS 
Exports. 
‘ . Difference of Per 
No. of Register Tons Weight of « 
Date. Vessels. Tonnage. Cargo carried. oo ee ect 
Tonnage. 
1852 | 39,361 8,242,702 6,418,245 — 1,824,457 —22 
1853 | 44,779 | 9:447:104 | 7,316,457 | —2,130,647 | —22 
1854 | 43.494 | 9,507,721 7,639,473 | —1,868,248 | —19 
1855 | 42,597 9,538,231 8,370,363 — 1,167,868 —12 
June, 1858, HENRY WRIGHT. 
Notice of the Instruments employed in the Magnetic Survey of Ireland, 
with some of the Results. By the Rev. H. Luoyp, D.D., M.R.LA. 
Tue Irish portion of the magnetic survey of the British Islands was com- 
menced in the beginning of August last, and is now nearly terminated, 
nothing remaining for its completion but the determination of some of the 
instrumental constants. The observations in the northern half of Ireland 
were made by Profs. Galbraith and Haughton, and those of the southern 
half by Dr. Lloyd and G. Johnstone Stoney, Esq. The instruments employed 
were similar in the two divisions of the island, and consisted of a theodolite 
magnetometer, and of a dip circle furnished with an apparatus for the deter- 
mination of the earth’s magnetic force in absolute measure. The compara- 
bility of these instruments was established by observations taken at Dublin 
at the commencement of the survey. The elimination of the magnetic changes 
will be effected by means of simultaneous observations made at the mag- 
netical observatory of Dublin. The theodolite magnetometer for the mea- 
surement of the magnetic declination differs somewhat from instruments of a 
similar nature hitherto in use,—the ditference consisting in observing the sun 
(or other celestial object) by reflexion, and transferring the transit adjust- 
ments to the axis of the mirror employed for that purpose. By this arrange- 
ment, the observing telescope is always horizontal, and in readiness for the 
magnetic part of the observation. The instrument is furnished also with the 
means of determining the horizontal component of the magnetic force in 
absolute measure ; but this was not employed, the determination of the total 
intensity by means of the dip circle leaving nothing to be desired. The ap- 
paratus required for this latter determination consists of two additional needles, 
