R B P 0 R T 
BY MESSRS. C. R, BLACKETT AND A. N. PEARSON ON THE 
SUITABILITY OF THE RIVER YARRA FOR THE IRRIGATION 
OF THE BOTANICAL GARDENS. 
Department of Agriculture, 
Agricultural Laboratory, 17A and 19A Queen-street, 
Melbourne, 16th April, 1890. 
Sir, 
We have the honour to report that, acting on instructions received conformably 
with vour memorandum, No. 0 . 89/1 6289, of the 27th August, 1889, to the Honorable 
the Minister of Mines, we have undertaken and completed a critical examination of the 
river Yarra, with a view to ascertaining if the water of that river taken from the 
surface only, anywhere near the present pumping station, could be used for irrigating 
the Botanical Gardens. 
Our instructions were received on the 31st August, 1889, and we immediately 
placed ourselves in communication with Mr. Guilfoyle, the Director of the Botanic 
and Domain Gardens. This gentleman stated that at that time there was no trouble 
with the water obtained at the pumping station, there* being then a rapid current of 
fresh water due to recent rains, and that it was only between the 1st October and the 
31st March that danger from the saltness of the river was to be apprehended. He 
promised to let us have the earliest intimation of the water becoming too salt. We 
thereupon wrote to you on the 5th September, 1889, stating that we could not for the 
reasons mentioned commence our examination until some time in the month of 
October ; we also mentioned that it would be necessary to gather samples of the water 
systematically for a month or two, and that we purposed paying special attention to 
the difference in the quality of the water at different depths, at different positions up 
the river, at different tidal periods, and at night and day. 
No report reached us from the Botanic Gardens as to the saltness of the river 
during the months of September and October, and on the nth November we again 
communicated with the director on the subject, receiving reply that the water was still 
fresh, as shown by a crude test which was being applied at the pumping station, a test, 
namely, as to its readiness to produce lather with soap. 
On the nth December we sent down and obtained a sample from the w r ell 
which receives the river water at the pumping station. This sample, on analysis, was 
found to contain 67 parts of chlorine (representing 110*4 parts of salt) per 100,000. 
We were informed that this was the first day on which the river had shown indications 
of being injuriously salt, and we decided to commence the examination forthwith. 
Before beginning operations it was necessary to decide upon the limit of saltness 
which could be safely allowed in water intended for irrigating the Botanic Gardens. It 
was hoped that this question would have been settled bv direct experiment, but the 
experiments commenced to this end in the small conservatory attached to the Agricultui al 
Laboratory were stopped through damage done to the experimental plants by mice, 
and, as it was too late in the season to begin the work over again, the experiments had 
to be put off until next season. A limit may, however, be fixed by indirect methods. 
Thus, an outside dressing of salt in ordinary farming is 5 cwt. per acre, and this 
amount should not be given often unless there be a heavy rainfall and free drainage, 
so- as to allow the soil to be properly washed. Suppose, now, a water to contain 50 
parts of salt per 100,000, then soil irrigated with 1 in. depth of such water would 
receive 1 cwt. of salt per acre, and irrigated with 10 in. depth of such water it would 
receive half-a-ton of salt per acre, which, as we have seen, is an excessive amount. 
