626 ON THE FIGURE, DIMENSIONS, AND MEAN SPECIFIC GRAVITY OF 1 HE EARTH. 
equations is +2-05, which would diminish the probable error of the results in the 
proportion of 5 : 4. 
Summary. 
We mav state the results of this paper briefly as follows : — 
1st. The four bases of verification, when their measured lengths are compared M'ith 
their lengths as calculated from a mean of the Lough Foyle and Salisbury Plain bases, 
show the following discrepancies, expressed in feet : 
Hounslow. 
Misterton Carr. 
Rhuddlan Marsh. 
+0-173 
— 0-191 
+ 1-596 
Belhelvie. 
+0-240 
compression =: 
1 
2nd. The elements of the spheroid (B) most nearly representing the surface of 
Great Britain are — 
feet Oj. miles. 
Equatorial semidiameter =20926249 = 3963-305'l 
Polar semidiameter =20856337 = 3950-064 J 
3rd. The elements of the spheroid (C) most nearly representing the whole of the 
measured arcs considered in this paper are — 
299-6S 
feet Oj. miles. 
Equatorial semidiameter =20924933 = 3963-057 
Polar semidiameter =20854731=3949-760 
j.compression - 
:98-u7 
4th. The lengths of the degrees of latitude and longitude in Great Britain are a 
in the following Table: — 
Mean 
latitude. 
From Ord. Survey, Spheroid (B). 
From Spheroid (C). j 
Length in feet of 
Length in feet of 
Length in feet of 
i 
Length in feet of j 
1° of latitude. 
1° of longitude. 
1° of latitude. 
1° of longitude. j 
O 
50 
364936-33 
235227-42 
364912-12 
235214-58 ! 
51 
364999-14 
230312-27 
364975-19 
230299-77 ’ 
52 
365061-50 
225326-39 
365037-81 
225314-19 
53 
365123-34 
220271-15 
365099-92 
220259^23 : 
54 
365184-58 
215148-11 
365161-41 
215136-58 
55 
365245-15 
209958-83 
365222-23 
209947-61 
56 
365304-96 
204704-93 
365282-29 
204694-04 
57 
36.5363-96 
199387-90 
365341-53 
199377-33 ! 
58 
365422-06 
194009-37 
365.399-88 
193999-13 
59 
365479-20 
188571-00 
365457-26 
188561-08 
60 
365535-30 
183074-50 
365513-59 
183064-93 
Explanation of the Plate. 
PLATE XXXIV. 
Is a diagram of the triangulation of the United Kingdom, and is one of the plates 
which has been engraved at the Ordnance Survey Office to illustrate the 
Account of the Trigonometrical Survey of the United Kingdom which is 
now in the press. 
