THE GARDENER'S ASSISTANT. 



Progress of Solar Radiation from Morning to Evening. 



Thermometer. 



Time. 



In Sun. 



In Shade. 



Difference. 



9 A.M. 



93° 



68° 



25° 



»1 „ 



103 



69 



34 



10 „ 



111 



70i 



40i 



10i „ 



119 



71 



48 



11 „ 



124 



71* 



52i 



Hi „ 



125 



72i 



52^ 



12 M. 



129 



73 



56 



12A p.m. 



132 



74 



58 



1 „ 



141 



74i 



66i 



H „ 



140 



75 



65 



2 „ 



143 



75i 



67i 



2| „ 



138 



76 



62 



3 „ 



138 



76i 



61i 



H „ 



132 



77 



55 



4 „ 



124 



76 



48 



44 „ 



123 



77 



46 



5 „ 



112 



76 



36 



$h ,, 



106 



75 



31 



6 „ 



100 



73 



27 



Means 



124| 



73i 



5ii 



tween three and half-past four p.m.; but the 

 power of the sun's rays was greatest between 

 one and two p.m. Although the observations 

 were only taken for one day, yet it was well 

 selected for the purpose by one who was ac- 

 counted an authority on the subject. As trust- 

 worthy observations of this nature are important 

 to the subject in hand, the following additional 

 extract is given from the same work: — 



"The mean results of five series of experi- 

 ments, conducted with every possible precaution, 

 are contained in the following table, showing 

 the power of the sun's radiation from half-past 

 nine a.m. to half-past six p.m., in the month of 

 June: — 



Progress of Solar Radiation from Morning to Evening, 

 in June, upon an average of five experiments. 



Time. 



Force of Sun's Rays. 



94 A.M. 



32° 



10* „ 



46 



111 „ 



55 



12i P.M. 



63 



if „ 



65 



2j „ 



63 



s| „ 



58 



41 



% :: 



49 



35 



4 „ 



29 



Here it will be observed that the force of the 

 sun's rays at half-past nine a.m. is on the average 

 32°, and that it increases between one and two 

 p.m. to its maximum, 65°, or to rather more than 

 the double of what it was at half-past nine a.m. 

 It will also be seen that it increases rapidly be- 

 tween the hours half-past nine, half-past ten, 

 half-past eleven, and half -past twelve; and then 

 during the next two hours the force is nearly 

 uniform. 



Moreover, the average force of the sun's rays 

 in the three hours before twelve noon, is, accord- 

 ing to these observations, about 44°; and in the 

 three hours after twelve it is 62°. From this it 

 is evident that a wall with a west aspect must 

 be much warmer than one with an east aspect. 

 The sun shines in a clear day as long on the one 

 as on the other, but not with equal intensity. 

 For three hours before noon the sun shines on 

 the east aspect at the same mean angle as he 

 does on the west aspect for three hours after 

 noon; but during the latter period his rays 

 have, according to the above observations, 

 about 40 per cent greater intensity. The wall 

 with the west aspect must therefore become 

 much more heated than the one with the east 

 aspect. After half -past three p.m., the power 

 of the sun's rays begins to decline considerably, 

 but as some compensation for this they impinge 

 more directly on a west wall. 



The southern aspect being the most import- 

 ant, requires to be taken first into consideration. 

 It may, according to circumstances, face either 

 directly south; or it may be inclined to the 

 south-east, so as to face the sun about eleven a.m.; 

 or it may incline to the south-west, to face the 

 sun about one p.m. In parts of the kingdom 

 where the summer heat is sufficient to ripen 

 Peaches and Nectarines on a wall facing the 

 sun at eleven a.m. that aspect should be chosen, 

 as in that case the adjoining walls can proceed 

 at right angles, and afford two good western 

 aspects, on which the sun may commence to 

 shine as early as eleven a.m., so that Apricots, 

 Plums, Cherries, and Pears, could be ripened 

 to perfection upon it. But, if the heat against 

 an aspect thus inclined an hour to the east of 

 the meridian is not sufficiently intense to ripen 

 Peaches satisfactorily, the aspect must face the 

 sun at noon; and where the climate is still 

 colder, it will be advisable to turn the aspect to 

 face the sun at one p.m. The walls should, if 

 possible, be at right angles to each other. 



With regard to the aspects of the other walls, 

 it would not be desirable that each should receive 

 an equal amount of sun-heat in the course of the 

 day; for if this were the case, the consequence 

 would probably be that although many of the 

 finer varieties of Pears, &c, could be grown on 

 both sides of the wall, yet none of the fruit 

 would ripen to perfection. The eastern aspect 

 must be planted with such things as are most 

 suitable, chiefly summer or early autumn fruits ; 

 for, owing to the ripening period of these being 

 nearly that at which the hottest weather occurs, 

 an indifferent aspect will ripen them tolerably 



