1887.] H. F. Blanford — Inflaence of Indian Forests on the Bainfall. 9 



50,000 square miles, has been increased in a very remarkable degree, 

 and I am unable to assign any other probable cause for this than that of 

 the protection and consequent restoration of the formerly wasted forests. 

 The evidence thus afforded in favour of the influence of forests on 

 rainfall appears to me to be of considerable weight and importance, in 

 virtue both of the magnitude of the area yielding it and of the apparent 

 distinctness of the result. With one exception and one only, it fulfils 

 all the conditions of a rigorous test case. The area is one and the same ; 

 the history of the changes to which it has been subject are definitely 

 and accurately known ; and, as will be shewn elsewhere, the rainfall 

 registers, if but few in proportion to the area, are sufficient to afford a 

 datum the probable error of which is small in comparison with the mag- 

 nitude of the effect shewn. The only remaining points to which excep- 

 tion may conceivably be taken are the trustworthiness of the records 

 used, and the sufficiency of the periods compared to yield valid averages. 

 On the first of these points, I can add but little to what has been 

 already written in the introduction of Vol. Ill, Part 1, of the Indian 

 Meteorological Memoirs. Speaking from recollection (for I have been 

 unable to obtain the desired verification of the fact from official records), 

 I believe that new rain-gauges, of Glaisher's pattern, from one of the 

 principal London makers, were furnished to all the stations the registers 

 of which are here dealt with, about the year 1867, at all events before 

 1870, that is to say, at or near the beginning of the period for which the 

 registers are complete, and there are therefore no grounds for suspecting 

 that the increase of the registered rainfall during the last ten years has 

 been influenced by a change in the instruments used. And this is the 

 most important consideration. With respect to the registering agency, 

 as far as I have information^ it has been the same throughout. Dr. S. C. 

 Townshend, who was Sanitary Commissioner of the Central Provinces, 

 and who in 1868 established the observatories, which, in 1875, were 

 incorporated in the Imperial system, took much personal interest in 

 all the meteorological work of the province, and there is no doubt that 

 his action was attended with beneficial results. But this change, like 

 that of the instruments, dates from the beginning of the period now under 

 consideration ; at all events from 7 or 8 years anterior to 1875. 



On the second point, namely, the sufficiency of the periods compared 

 to yield valid averages, I have ascertained that a ten years' register of 

 the Central Provinces' stations, Jubbulpore and Nagpur, has a probable 

 error of 5 per cent., namely, in the case of Jubbulpore of 2*7 inches, in 

 that of Nagpur of 22 inches, and these may be taken as fairly illustrative 

 examples of the whole province. These, however, are the probable errors 

 of individual stations, and, as will be further demonstrated elsewhere, the 

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