491 



although it is there uncertain when rain may fall, it is certain 

 that an abundant supply does fall ; and the hand of man alone 

 is wanting to preserve the supply, and regulate its use. 

 Where natural resources exist, but require art and industry 

 for their development, the field is open for the combination of 

 science and skill, the profitable investment of capital, and the 

 useful employment of labour,' 



" The preceding extract distinctly shows (what indeed is 

 confirmed by other travellers) that civilized man will be un- 

 able to form permanent settlements in the extensive and 

 fertile regions forming the interior of Anstralia, unless he can 

 call to his assistance means adequate to overcome the formi- 

 dable difficulty presented by want of water, during several 

 months of the year. The method I have invented, by which we 

 can readily and cheaply cover even a large surface of water, 

 will, no doubt, greatly facilitate the accomplishment of what 

 would be otherwise, in many localities, unattainable. Instead 

 of the expense of vaulting over reservoirs, or covering tanks, 

 we can now make the water itself support its own roof- — a 

 roof, it is true, thin and delicate of structure ; but, neverthe- 

 less, by reason of its impermeability, not less capable of pre- 

 venting evaporation than if it consisted of the most solid 

 masonry. The floating carpet, or roof, possesses the great 

 additional advantage of rising or falling, according as the 

 quantity of water in the reservoir increases or diminishes, so 

 that all access of air to its surface, and consequently all eva- 

 poration, is prevented. This covering, being opaque, will keep 

 the water perfectly in the shade, a circumstance, which, com- 

 bined with deficient ventilation, would in itself much retard 

 evaporation, as is exemplified even here by the wetness of 

 roads overshadowed by trees, and by the water remaining in 

 ditches, when covered by lemna or duck-weed, so long after 

 the summer heats have dried up all other ditches in their 

 neighbourhood. In some parts of Russia, where the weather 

 is very hot in summer, the peasants use water-tubs with float- 



