Guildford, West Midland, Helena (?), and Present levels. Prom 
Susannah Brook to t lie east this profile was completed by inspection 
of the ground, not by theodolite levelling, owing to lack of time and 
a failing light. The levels observed were corrected to survey datum 
by the height of Herne Hill siding, which is on the (kiversham level 
(17). Profile No. 4 (at Ppper Swan) shows the Caversham, Guild- 
ford (obscurely), West Midland, and Present levels, and an inter- 
mediate terrace between the Guildford and West Midland levels. 
The last is interpreted as a sliff-off terrace (11), a type likely to be 
encountered upstream where corrosive power is at its height. The 
West Midland level was identified with certainty by plotting the 
gradients of the levels to scale on squared paper, which rendered its 
harmony with the system apparent. As with No. .4, this profile was 
co-ordinated with survey datum from the height of Upper Swan 
Siding (17), which is also on the Caverslinm level. Profile No. 5 is 
an idealised representation of tile levels as shown by both rivers. 
Profile No. 0 shows the gradients of the levels along the course of 
the Swan, and, like Nos. 4 and 4, gives a very clear idea, of the 
divergence of the levels due to rejuvenation, and of their converg- 
ence during stillstand or subsidence in upstream sections. It was 
by means of this diagram that the truncation of the West Midland 
terrace in the Guildford District was first recognised. 
The heights of the levels for the various profiles are tabulated 
below. The levels are numbered in descending order of age; heights 
are stated in feet. 
Guildford. 
Albion 
IJ pper 
Town, 
Swan. 
— 
Helena. 
Swan. 
Swan. 
Swan. 
a. 
b. 
a, b. 
1 
*, . 
... 44 
44 
44 44 
62 
70 
•') 
... 
» v ♦ *• * * 
37 
29 29 
53 
05 ? 
4 
, . . 
25 
25 
21 ? 21 ? 
23 
32 
4 
... IS 
... 
... ... 
18 
5 
... 
12 
16 
10 8 
8 
11 
Tin; (Volks of Bros ion.- Il will be conceded that the interval 
between two succeeding and persistent levels indicates a cycle of 
erosion. The levels here recognised correspond to four such cycles. 
The first, or Guildford cycle, represents the difference between the 
Caversham and Guild lord levels, and was the initial cycle. It was a 
period of subsidence followed by stillstand (the drowning referred 
to by *1 ul son and Somerville)- The interval between the Guildford 
and West Midland levels, or West Midland cycle , was a period of re- 
juvenation. After a pause the Helena cycle was initiated, we 
believe with further rejuvenation. After a second pause the Present 
cycle was ushered in with rejuvenation, which has now given place to 
stillstand. The amounts of entrenching done during these cycles 
