PART I.] General Otttline of Dr. von Pettenkofer s Views. 207 



ception appears not uncommonly to exist even yet as to the object which Dr. von 

 Pettenkofer had in view in advocating the system of water-level registration and 

 the method in which the data thus acquired should be interpreted, perhaps it may 

 be advantageous to give a general outline of what we ourselves conceive to be his 

 views on the subject. In his now celebrated lectures on "The Air in relation to 

 Clothing, Dwelling and Soil,"* a lucid description is given of the relation 

 which the air in the soil bears to the air above it : how the air in the pores of 

 the soil is kept constantly moving by the force of the wind passing over the 

 surface of the ground, and by the laws regulating the intermingling of gases — 

 change of temperature, diffusion, and so forth. 



As an illustration of the differences which soils present, he points out how 

 experience has shown that in some graveyards the decomposition of bodies is complete 

 in from six to seven years, whereas in others twenty-five or thirty years are 

 required before this is brought about ; so that it has become a matter of practical 

 import to ascertain the quality of the ground in this respect, when selecting 

 sites for cemeteries, as the interval which should elapse before a burying-ground 

 may be used again hinges upon the fact as to whether decomposition takes place 

 rapidly or not; hence it may happen that two cities with an equal population 

 may require cemeteries of very different extent. He mentions that several influences 

 combine to bring this about, but the principal one is the amount of, and the 

 facility for, the interchange of the air in the soil — gravelly and sandy soils acting 

 much more quickly than those of marl and clay. 



Elsewhere this savant points out that changes, such as these, are materially 

 expedited by variations in the degree of the soil-moisture : wood is preserved as well 

 in water as in dry air, but it rots when subject to alternations of dryness and 

 moisture. 



It is not on the particular degree of soil-moisture that Dr. von Pettenkofer lays 

 stress, but on the variations in it, and he suggests the fluctuation of the ground- 

 water as a convenient index of this, especially in Europe. With regard to India, 

 however, he throws out the suggestion that experience may show that the rain-fall 

 may serve as a clearer index than the water-level, as the former is not so irregularly 

 distributed throughout the year as in Europe.f Mr. H. F. Blanford, in a work 

 recently published, also points out the marked difference which exists between 

 European and Indian meteorological manifestations, and remarks that "order and 

 regularity are as prominent characteristics of our atmospherical phenomena as are 

 apparent caprice and uncertainty those of their European counterparts."! 



Grranted that certain organic or inorganic processes take place in the soil and 

 give rise to various diseased conditions, it would still be necessary to show how 



* Bezic.hvngen cler Liift :u Kleiduiuj WoUmimj und Boden, 1872. 

 f Verbreitungsart der Cholera in Tndien, 1871, S. 95. 

 J T7ie Indian Meteornlogisfst Vade Mecum, 1877, p. 144. 



