either to start or to alight across the direction of the wind, it would appear that a ground of not less than some lOO or 150 acres in extent would be desirable. At the present time the Author believes that the provision of well-appointed flight-grounds of the area stated in different parts of the country would do more to further the cause of aviation than an equal expenditure of money in any other direction."It is possible that at some future time the landing-gear of machines may be so far improved that it may be found possible to alight on the ordinary high road; also it may be that sections of the high road will be specially widened and freed from adjacent obstruction to serve in cases of emergency. It is clear, however, that the general use of the high road for this purpose would in any case be open to very grave objection.
"It might be thought that the setting apart as flightgrounds of such considerable areas of land as above indicated would impose too serious a financial burden on flying, at least for some time to come, to be commercially possible. It is, however, to be borne in mind that with proper management such grounds could, especially if duplicated, be utilized for grazing purposes: thus, if an area of 200 acres were available, a herd of some few hundred head of cattle could be grazed, being transferred from one section of the ground to another from time to time. It is therefore evident that, under favourable conditions, the commercial aspect of the problem is by no means outrageous, even during the period that must intervene before flying as a mode of locomotion can become in any sense popular. Beyond this, assuming that the flying-machine is able to justify its existence apart from its employment by the Services, there seems no reason to suppose that the returns of a well-equipped flying-ground might not easily become far greater than the agricultural value of the land concerned, which at the best is but a few pounds per annum per acre."
§ 107. The Fourth Arm in Peace Time. Depreciation and Obsolescence. A somewhat knotty point is that of the duration of the service life of aircraft. So far no definition has been generally accepted. The
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