SANITAKY EFFECT OF WOODLANDS RAINS. . 285 



this place and a malarious district to tbe south, and while this remained 

 the place was healthy. This was cut down, and presently the south 

 winds brought in the fevers from the pestilential district. Manziana, 

 a place lately almost wholly free from malaria, has suffered in like man- 

 ner since the shepherds have set fire to an olive forest adjacent. Asimilar 

 phenomenon was observed at Sezz6. At Supino the arrondissement of 

 Frosinone formerly passed for healthy, but since the cutting off of a 

 piece of woods the malaria soon became seated, and, in a httle time, 

 many of the inhabitants fell victims to disease.^ 



Lancisci relates that the insalubrity of Rome was notably increased in 

 the days of Gregory XIII, when a pine forest to the south was cut down 

 because infested by brigands. 



On the other hand, cases are not wanting to prove the happy eflect 

 of planting trees. One of the most striking of these is that of the 

 Abbey of Trois-Fontaines, near Eome, which passed for some time be- 

 lore, as one of the most insalubrious and fever-breeding places in all the 

 campagna of Rome, but which for the last three years has enjoyed 

 some relief from a young plantation of the Eucalyptus ; and the success 

 which has followed this experiment will doubtless lead to further plant- 

 ing, and, perhaps, to the restoration of a region hitherto notoriously 

 unhealthy to its ancient salubrity. Examples of success in counter- 

 acting the pestilential emanations from marshes by planting this tree 

 are also reported from Algeria. It is supposed to operate partly by 

 absorbing humidity from the soil, and partly through the camphor- 

 ated exhalations from its leaves, puritying the atmosphere to their lee- 

 ward. The miasms appear to be condensed by filtering through the 

 foliage of trees, while the oxygen, liberated by the leaves, contributes 

 still further to purify the air.^ The direct and incidental benefits, in a 

 sanitary point of view, that are derived from the presence and proper dis- 

 tribution of woodlands cannot be considered in detail in this connection. 



EAINS. 



As has been already remarked, the extent and distribution of our 

 original forests was largely dependent upon the amount of rain fall and 

 its due proportion in the several seasons of the year. There is no part 

 of the country unfavorable to forest-growth, where these essential con- 

 ditions exist in proper degree ; although from other causes, as, for exam- 

 ple, annual running fires, a region may not have borne trees within our 

 recent historic period. 



From records, kept through more than CO years at military posts — ob- 

 servations at academies and colleges, and by voluntary observers under 

 instructions from the Smithsonian Institution, and more recently from 

 records made by specially qualified observers under the Weather Signal 

 Service of the War Department, we are enabled to judge as to what this 

 distribution of the rain-fall now is, and in some instances what it has been 

 through a long series of years.^ It is proper to notice the fact that the 

 results thus far obtained do not justify the statement that the amount 

 of rain falling annually has varied materially, taking a series of years 

 together, or that, whether forests are present or absent, there is any 

 notable increase or decrease of the general average amount in different 

 years. In fact, this cannot be determined with any degree of precision 

 until these series of records shall have been carried through a very long 

 period. 



' Eevue des Eaux et Forets, 1875, 363. 



* L'Igiene della Campagna e dUa di Eoma, P. Balestr^. Borne, 1875. 



