LIEUT. -COL. A. E. CLAEKE ON STAND AEDS OF LENGTH. 
459 
Standard Bar of the Cape of Good Hope. 
The 10-feet Cape standard is a bar similar in construction to the Ordnance 10-feet 
standard. In April 1844 one hundred comparisons were made between these bars at 
Southampton, giving the difference of length 
O, — B = 50-08. 
These comparisons were renewed in January 1868 and September 1869, fifteen being 
made on six days in the former month at a temperature of about 41°, and fifteen on five 
days in the latter month at about 59°*5. 
The reduction of the observations by the method of least squares gives the difference 
of length at 62°, 
Q 1 -B=51T2±0-25. 
The agreement of this with the comparisons of 1844 gives much confidence in the 
stability of these bars, and is almost as remarkable as the result obtained from the Indian 
bar I A (see ‘ Comparisons of Standards,’ page 255). 
The Spanish Standard. 
The iron four-metre bar belonging to the Spanish Government, which was sent to this 
country in the autumn of 1869, is a copy of the geodetic standard of Spain. This 
standard itself was constructed from Borda’s double-toise No. 1, of which the length is 
3-8980732* metres. The description of this standard, and a very full and elaborate 
exposition of the methods of comparison, is given in the work entitled “ Experiences 
faites avec l’appareil a mesurer les bases appartenant a la Commission cle la Carte 
d’Espagne ” (Paris, 1860). 
This bar is constructed of two plates of iron in the form of a _L, the upright plate 
being nearly 5 inches in depth, and the horizontal plate 3^ inches in width. These 
plates are connected by thirteen pairs of angle-pieces. Four thermometers, which are 
Centigrade and of very excellent workmanship, are attached at the sides of the bar, being 
of course removable at pleasure. A levelling-apparatus is attached at the upper edge 
of the bar. The bar is lifted by two pairs of handles ; it is not enclosed in a box when 
in use as a measure, and has no other protection than paint. For travelling it is pro- 
tected in a very strong box. 
On the upper edge of the bar are inlaid five small disks of platinum, and on these are 
drawn fine lines which mark off the lengths of four metres. The part of each line to be 
observed is the extremity contiguous to the edge of the bar. The lines are unfortunately 
not very fine, though otherwise very well drawn. 
The following is the certificate of this bar : — 
“ Begle enfer appartenant au Gouvernement Espagnol. Pour chaque degre du ther- 
mometre centigrade elle se dilate de 
0 ram -043193 + 0 mm -000009, 
elle a ete comparee avec le regie en platine, etalon geoclesique de 1’Espagne, lequel etalon 
* Base du Systeme Metrique Decimal, tome iii. pp. 139, 228. 
