67 



Discussion. 



Mr. F. B. Gipps : — Mr. Abbott has entertained us with 

 a most interesting paper on the effects of ring-barking or 

 •deforestation, which is the more valuable on account of its being 

 the result of actual observation. If another such enthusiast, with 

 opposite views and having similar advantages for observation, 

 could be induced to enlighten us with the results of his 

 investigation, we might by comparison of notes be able to arrive 

 at more decided conclusions on this really most important subject, 

 especially in a country like this so liable to droughts. It is to be 

 hoped that this discussion may discover such an observer. For 

 my own part I have little co add likely to assist in such conclusions, 

 •except an attempt to account for the breaking out of springs 

 alluded to by Mr. Abbott, and to suggest some reasons why forests 

 should attract rainfall. There is no questioning his premise that 

 the breaking out of springs in a country denuded of its forests 

 by ring-barking is largely affected by its physical and geological 

 features. From his description of the geological features of the 

 range of country covered by his observation, it may safely be 

 presumed that the springs are of deep-seated origin, whilst his 

 account of the topography of the country shows that it offers a 

 favourable position for the bursting out of such springs when 

 relieved to a certain degreee of atmospheric pressure. But the 

 flow of such springs is at all times more or less affected by the 

 •condition of the atmosphere. For instance, the approach of heavy 

 rains is often indicated hours before by their suddenly bursting 

 out afresh, or by their larger increase in volume because of the 

 decrease in the pressure of the atmosphere. Doubtless the 

 breaking out of springs noted by Mr. Abbot, is due to just the 

 same decrease of pressure, only from another cause. In the latter 

 instance this decrease is produced by the effect of the solar rays 

 •on the exposed surface of the ground, which gradually heats the 

 lower stratum of air, causing it to expand. This expansion 

 lessens the atmospheric pressure and thus induces the flow of 

 springs. Perhaps there is no part of the country where this 

 favorable condition for constant flowing springs can be better 

 exemplified than at the summit of the Great Divide in the vicinity 

 of Mount Kosciusko. Here we find innumerable perennial springs 

 jutting out in every direction on the treeless table lands and 

 slopes, whilst in the forests, only a short distance below, not a 

 sign of a spring hardly is to be seen in summer time. This 

 conclusively proves that there is a greater pressure of atmosphere 



