114 nvponn=1862, 
instruments were nearly ready for trial and verification, he proposed to devote 
his approaching holidays to profit by the opportunity of gaining practical 
instruction and experience in their use; proposing at the same time to study 
Professor Thomson’s electrometer—the only apparatus, he says, which holds 
out the hope of satisfying the present exigences of science, which require 
continuous registration—and to obtain the other meteorological instruments 
and compare them with the Kew standards. 
The first part of the report is dated July 25, 1861; the second part 
November 16, 1861, and gives an account of his second visit to the Kew 
Observatory. It is prefaced by acknowledgements of the kindness and help 
he received from Messrs. Stewart and Chambers at the Observatory, from 
General Sabine, Mr. Gassiot, and the whole of the “ directing Committee,” 
from the British Association, and from the Royal Society. 
He arrived in London on the 24th of August, and finding General Sabine 
absent in Wales, proceeded at once to the artists, Adie, Barrow, and Gibson, 
who informed him that his instruments were at Kew, whither he lost no time 
in repairing, and where the Director arranged that the work should begin at 
once. Prof. de Souza took up his abode at Richmond, and went daily to the 
Observatory, remaining there from 9.30 a.m. to 5.30 p.m. He speaks of the 
great kindness, instruction, and constant assistance which he received from 
the Director and the whole personal staff of the Observatory, in their different 
degrees and functions, in the practical study of the instruments. This study 
consists, he says, in setting them up in the trial house precisely as they are 
to be set up at Coimbra, in determining their constants, in repeatedly 
observing the magnetic elements with them and comparing the results with 
those of the Observatory, and in reducing these observations. In the course 
of the observations some little faults, which would otherwise have escaped 
notice, were discovered in the instruments; to correct these the artists were 
repeatedly called to Kew, or the Director conferred with them in London. 
The collection of magnetic instruments consists, firstly, of the magneto- 
graphs which register continuously the horizontal force, the vertical force, 
and the declination ; and, secondly, of the portable instruments, viz. Barrow’s 
circle for the absolute determination of the inclination, with the apparatus 
for determining the total foree by Dr. Lloyd’s method; and the unifilar, by 
Gibson, with its apparatus for the absolute determinations of the declination, 
and of the horizontal force by the method of vibrations and deflections. 
The magnetographs are accompanied by three telescopes, for the direct 
observation of the magnetic elements when requisite, and by all things 
necessary for beginning work as soon as they are established—utensils 
for photographic manipulation, a year’s supply of chemical ingredients, 
waxed paper, spare bell-glasses, chimneys and mirrors, coloured glasses for 
the photographic house, &c. The portable instruments, which are indispen- 
sable in an observatory, being also proper for the observations of a magnetic 
‘survey, are conveniently packed in portable boxes, and accompanied by a 
tripod stand. 
The existence of the Astronomical Observatory at Coimbra makes it possible 
to dispense with a transit-instrument and clocks, but a good chronometer is 
essential ; and by the kind aid of the Hydrographer, Admiral Washington, to 
whom General Sabine wrote on the subject, Prof. de Souza received permission 
to purchase one of those examined at Greenwich, and guaranteed by the 
Astronomer Royal, at the price which would be paid for the same by the 
British Admiralty. 
«Besides the barometer required for the ordinary direct observations,” 
