SCIENCE AND INDUSTRY. 
These experimental investigations presupposes an ample supply of .the plants. 
This, no doubt, exists already in many of our creeks and water-ways, but the need 
for destruction in many places will still exist. 
The methods that have been either tried, or proposed, are as numerous as 
the various attempts at utilization. They might be classified into Biological, 
Chemical, and Mechanical. 
Biological methods usually involve the introduction of some plant or insect 
pest. There is a leaf-spot disease that kills the whole leaf of the water hyacinth, 
and is widely distributed. This might be of service as a continuous method of 
destruction, and its introduction should be easily accomplished. The native 
home of the pest is usually explored to discover any natural controls; but we 
are not likely to meet very much success with this method, other than the leaf- 
spot fungus, as the water hyacinth is a very serious pest in its own country. 
There does not appear to be any insect pest of any value as a destructive agent 
of water hyacinth. The introduction of another weed—or water pest—Philotria 
canadensis, has been suggested; but the cure may turn out to be as bad as the 
disease. . : 
Under Chemical methods, there may be mentioned chiefly the use of copper 
sulphate, arsenic compounds, and kerosene or gasoline. The use of poisons 
is usually fraught with too much risk to animal life, as the strength of the 
solutions that would be required to kill the weed would be sufficiently strong 
to kill animals that might drink the water (cattle, horses, &c.), and also birds 
and fish, and probably other vegetation as well as the hyacinth. As the plant 
produces an abundance of flowers and seed, a large amount of control could 
certainly he obtained by the use of a poisonous spray at the time of the 
pollination of the flowers. No doubt, the use of some of the deadly “ liquid 
fire” sprays used in the war could be cheaply applied to the destruction of the 
flowers, if not to other parts. The following up of any mechanical means of 
eradication by the search for and destruction of all young plants developing 
from seed is necessary for the complete success of any eradication process; 
hence, any method that will prevent the wholesale production of seed must be 
of great value, especially if combined with some effective mechanical means ot 
destruction. The use of an arsenical solution (Harvester Compound) from barges 
fitted with sprays and pumps, was experimented with years ago in Florida; but 
the cost was found to be excessive—£4 per acre—as compared with various 
mechanical methods, e.g., in Queensland, 30s. an acre. 
It is considered that the remoyal of the plant by mechanical means would be 
the most economical that could be adopted, and this may then be followed by 
the process of potash extraction from the removed plants. 
The most successful form of mechanical destructor appears to consist of some 
torm of punt or barge fitted with a stern paddle-wheel, having a double bow or 
outriggers, which, being forced into a mass of weeds, would cause them to gather 
towards the centre of the boat. Here an inclined carrier, consisting of an 
endless travelling band, with a flap set below the water’s edge, would convey 
the weed to rollers where it would be crushed, and the mat delivered by the 
same means into a barge alongside. Cutting devices of a mechanical nature 
have also been suggested for operating in thick masses of the weed. 
On the Clarence and Tweed Rivers, it is a common occurrence for the wire 
ropes of ferry punts to be broken by the down-stream pressure of great masses 
of the weed, and a common method of getting rid of the plant is to place a 
floating barrier across the river until a great area of weed collects, then either 
to drag the mass on to the land or float it down to the salt water. Such methods, 
are, however, only spasmodic, and much money has been spent by shires and 
municipalities in periodic attacks, which bring about only temporary relief. 
Systematic and concerted action will be necessary to clear definite areas, but 
the utilization of the plant for potash production may convert large areas of 
what is now a nuisance into a valuable asset. 
The details of a process for the recovery of the potash salts on a commercial 
scale (taken from Malay States’ Bulletin, VI., 312), will serve as a conclusion 
to this general summary of the present vexed question of the water hyacinth, 
i the hope that further experiments will be undertaken along the lines indicated 
above. { 
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