iSyi.] PROTECTION OF FRUIT-TREES. 309 



satisfied that it is so, for having had some experience of most of the 

 materials commonly used, I have observed that they all tend to increase 

 the mean temperature of the day by raising the actual temperature of 

 the night, while they have much less influence in depressing that of the 

 day than is generally supposed. The weather itself is perhaps the 

 most effectual retarding agent we could wish in spring, north of the 

 Tweed at least. But granting that the application of the most ap- 

 proved protecting fabric acted so as to retard the activity of the 

 trees, what, it may be asked, is the good gained by the practice 1 

 Not much that is very apparent. Could we retard them for a month, 

 which is impossible, we should not then be able to pronounce them 

 past danger ; for there are not any grounds for assuring ourselves that 

 the more tender kinds of fruit — such as the Peach and Apricot — 

 are safe till the middle or end of May. It is from March till the 

 middle of May that danger to our fruit crops is most to be appre- 

 hended from frost ; and it is pretty clear, I think, that it is imprac- 

 ticable to retard the action of the trees to any considerable extent, 

 so as to tide them over the critical period in greater safety. Any 

 covering, be it light or heavy, if it is composed of non-conducting 

 material, will have the effect of surrounding the subject protected 

 by it with a more equable atmosphere, less liable to fluctuations of 

 temperature than the outer air. Every cultivator knows that such a 

 condition is the most favourable for steady progress in vegetable 

 activity, and that plants accustomed to such a condition are much 

 more susceptible of injury from any sudden decrease of temperature 

 than those that are subject to greater variations. Those, therefore, 

 that practise that system which is named retarding, practically ex- 

 tend the period of danger by hastening its commencement, for there 

 is no possibility of correspondingly shortening it at the other end, 

 and they also increase the danger by rendering their trees more sus- 

 ceptible of cold when extreme occasions arise. My own experience 

 is all in favour of the thinnest possible protection, to be put on 

 only when it is no longer safe to postpone doing so, and to be kept 

 permanently fixed as long as protection is thought necessary. In 

 my own case, circumstances leave me no choice between old her- 

 ring-nets and nothing. During the past three years they have been 

 used only in part for the purpose, there not being sufficient of other 

 fabrics to cover all subjects deemed worthy of, or in need of, pro- 

 tection, but during the present year nothing has been used except 

 old herring-nets. We use them twofold ; and scanty protection though 

 they may appear to be, we have proved them quite capable of carry- 

 ing safely through as good crops as there are agoing this year of 

 Apricots, Peaches, and the better kinds of Plums, &c. Yet we were 



