The farm which is healthiest is the most valuable, for there the profit is certain. On the other hand, on an unhealthy farm, however fertile it may be, misfortune dogs the steps of the farmer. For where the struggle is against Death, there not only is the profit uncertain, but one's very existence is constantly at risk: and so agriculture becomes a gamble in which the farmer hazards both his life and his fortune. And yet this risk can be diminished by forethought, for, when health depends upon climate, we can do much to control nature and by diligence improve evil conditions. If the farm is unhealthy by reason of the plight of the land itself, or of the water supply, or is exposed to the miasma which breeds in some localities, or if the farm is too hot on account of the climate, or is exposed to mischievous winds, these discomforts can be mitigated by one who knows what to do and is willing to spend some money. What is of the greatest importance in this respect is the situation of the farm buildings, their plan and convenience, and what is the aspect of their doors and gates and windows. During the great plague, Hippocrates the physician saved not merely one farm but many cities because he knew this. But why should I summon him as a witness: for when the army and the fleet lay at Corcyra[60] and all the houses were crowded with the sick and dying, did not our Varro here contrive to open new windows to the healthy North wind and close those which gave entrance to the infected breezes of the South, to change doors and to do other such things, and so succeed in restoring his comrades safe and sound to their native land? _The fourfold division of the study of agriculture_ V. I have rehearsed the elements and the purposes of agriculture, it now remains to consider in how many divisions this science is to be studied." "I have supposed these to be without number," said Agrius, "when I have read the many books which Theophrastus wrote on _The History of Plants_ and _The Causes of Vegetation_. "These books," said Stolo, "have always seemed to me to be fitter for use in the schools of the philosophers than in the hands of a practical farmer. I do not mean to say that they do not contain many things which are both useful and practical. However that may be, do you rather explain to us the divisions in which agriculture should be studied." "There are four chapters for the study of agriculture, of the highest practical importance," resumed Scrofa, "namely:" 1° What are the physical characteristics of the land to be cultivated, including the constitution of the soil; 2° What labour and equipment are necessary for such cultivation; 3° What system of farming is to be practised; 4° What are the season? at which the several farming operations are to be carried out. Each of these four chapters may be divided in at least two subdivisions: The first into (_a_) a study of the soil, and (_b_) a survey of the buildings and stabling.