10 ANNIVERSARY ADDRESS. 
evidence for elevation and subsidence of the land are about equal, 
the question before us being in which direction is the change 
going on now. In estimating the value of the evidence quoted as 
to the rate of rise in Queensland and South Australia, we must 
not forget that when engineers adopt the usual rule as to mean 
-sea-level—that is, as to the mean of high and low water at any 
time of the year—they assume that all such means are equal or 
represent a constant level, when in point of fact two such deter- 
minations of sea-level may differ by 8 inches or even more ; 
and, in the absence of a self-registering tide-gauge, or constant 
observations extending over a year, no levelling referred to the 
sea in the usual way is of any value whatever in such an investi- 
-gation as that required to determine whether the relative level of 
land and water varies. I have already shown that Mr. Ellery 
thinks there is no evidence of present rising in Hobson’s Bay; and 
the fact that at the time the engineering levels referred to were 
taken in South Australia and Queensland there were no self- 
registering tide-gauges to determine accurately mean sea-level, 
is sufficient to warrant us in hesitating before we receive the 
evidence as to the rate of elevation furnished from these Colonies 
which I quoted from Mr. Clarke’s report. In fact, it seems 
that the only observations of the relative level of land and sea in 
Australia taken with the accuracy which the investigation demands 
are those made with the Sydney tide-gauge, during the past twelve 
years, and they show conclusively that during that period there 
has been no appreciable change, and therefore we cannot say that 
the east coast at Sydney is either rising or falling. 
Every year now is adding some facts towards the better under- 
standing of the laws which regulate our rainfall, and every now 
and then some departure from the common course of things 
appears like a finger-post to indicate what is going on. You may 
remember that in 1882 I described a rain-storm that passed over 
the northern part of this Colony, travelling about ES.E, at 
the rate of 12 miles per hour. In 1883, the Fe rain- 
storm passed over Lerida Station, which is in Queensland 8° north 
