368 
NATURE 
These were bars of iron, and line standards, the lines 
being marked on gold pins at mid-depth of the bar, 
notches being cut in it for that purpose. They had been 
compared with the imperial standard in 1834, and a 
statement of their comparison was published in 1847 
in the account of the measurement of the base at Lough 
Foyle. 
Towards the close of the century, some important 
scientific operations for the improvement of the standards 
were undertaken by Sir George Shuckburgh. In 1796, a 
new standard measure subdivided in fine lines, and 
since known as “ Shuckburgh’s scale,” was constructed 
under his direction, by Mr. Troughton, together with a 
new comparing apparatus carrying micrometer micro- 
scropes. This is stated to have been the first occasion 
on which this mode of optical comparison was employed, 
being substituted for the beam compasses previously 
used. The Shuckburgh scale, which is now in the posses- 
sion of the Royal Society, consists of a brass bar 67} 
inches long, 1°4 in. wide, and 0'42 in. thick, It is a scale 
of 5 feet, divided by lines into feet, inches, and tenths of 
inches, each inch being numbered. It was adopted by 
the Standards Commission of 1819 as the scientific 
standard of length, as distinguished from the legal 
standard of the Exchequer. The length of the yard was 
laid down on the Shuckburgh scale from Bird’s standard, 
and it had also been accurately compared with each of 
the other standard yards previously mentioned, and their 
lengths had been transferred by beam compasses to the 
Shuckburgh bar. 
In pursuance of the recommendation of the Royal 
Commission of Weights and Meastires appointed in 1819, 
and of the Act of 1824, passed to carry their recommen- 
dations into effect, a new Exchequer standard yard for 
regulating commercial measures of length was constructed 
under Capt. Kater’s superintendence. It was not, how- 
ever, laid down from the legal standard yard, which, 
together with the legal standard pound, remained in the 
’ custody of the Clerk of the House of Commons, but from 
the length 1—36 in. of the Shuckburgh scale, which was 
considered by Capt. Kater to be identical with the impe- 
rial standard. 
The official standard yard constructed for the Ex- 
chequer, under Capt. Kater’s superintendence, in 1824, 
and intended for the verification of the local standard 
yards used by inspectors for comparing trade measures, 
consists of a slender brass rod with two wooden handles, 
as an auxiliary end measure, and a bed measure, being a 
bar of brass one inch square with rectangular steel ter- 
minations of the same width projecting above the surface 
ofthe bar. The distance between the interior faces of 
the steel terminations is intended to be equal to the length 
of the imperial yard. This yard bed and rod were 
used together from 1825 to 1870, for verifying all the local 
standard yards of similar though ruder construction. A 
standard yard, with the legal subdivisions marked upon it, 
and of improved construction, having a convenient com- 
paring apparatus attached to it, has since been substi- 
tuted, and is now used in the Standards Department. 
Four other standard yards of more scientific charac- 
ter were also made under Capt. Kater’s directions, 
and are now in the Standards Office. These bars of 
brass are of the same width and thickness as the Shuck- 
burgh Scale, and have the length of the yard defined by fine 
points upon gold studs in the middle axis of the bar, the 
thickness of the bar being reduced at its extremities one- 
half with this object. All these standard yards were con- 
structed by Dollond. By an ingenious contrivance the 
point at one end of the bar, not being placed exactly in 
the centre of the circular gold stud, was made susceptible 
of adjustment, by turning the stud round ; and after final 
adjustment of each yard and repeated comparisons with 
the Shuckburgh Scale, no perceptible error could be de- 
tected in any of them. A similar standard measure made 
for the Royal Society in 1831 was considered by the Com- 
mission to be the most favourable type of Kater’s yard. 
Having thus described the principal standard yard 
measures then existing, we may return to the operations 
of the Standards Commission. For determining the true 
length of the new standard yard, a provisional standard 
yard was employed by Mr. SHéepshanks, This was a 
new brass bar, called by him ‘Brass 2,” and was accu- 
rately compared by him with the standards deemed 
to be the most authoritative, and which had been dz 
rectly compared with the lost standard, viz. Shuckburgh’s — 
scale, Kater's yard made for the Royal Society, and the 
two Ordnance yards. 
petial standard were as follows :— 
In. 
Brass bar 2 = 36'000084 by comparison with Shuckburgh scale o-36 in. 
4) = 36000280 oe 33 zo-46 in. 
3) = 36°000229 i Kater’s Yard of 1831. 
iz Ordnance Yard, No. 1. 
3) = 36'000275 ” ” No. 2. 
31 = 36°000234 by mean of all. 
_Mr. Sheepshanks preferred 36'00025, as being suffi- 
Fic. 9.—Standard Wine Gallon of Queen Anne, } size. 
ciently near the truth, and in constructing the new stan- 
dard, he assumed as the basis of his proceedings— 
Brass 2 = 36'00025 in. of lost imperial standard, at 62° 
Fahr., and this conclusion met with the assent of the 
Commission. 
In the construction of the new standard of length, the 
following decisions were made by the Commission :— 
1. The length of one yard to be the standard unit of © 
length. 
2. After considering whether the measure of length 
should be defined by the whole length of the bar, that is 
to say, an evd-standard, or by the distance between either 
two points or two lines marked upon the bar, a /ime-stan- — 
dard was adopted in preference. 
3. For the material of the bar, gun metal or bronze 
composed of 
Copper . : 3 16 parts 
Tin ° . F » > hig 
Zinc - . ‘ : * pik 
” 
was adopted after a series of experiments by Mr. Baily, 
and was recommended by him as containing the pro- 
perties most essential for the construction of a standard 
intended to last through many ages, viz., almost perfect 
immunity from rust, with proved elasticity and rigidity. 
| Sep. 4, 1873, 
The results in terms of the lost im- 
