Vol. X. No. 237. 



THE AGRICULTURAL NEWS. 



173 



STUDENTS' CORNER. 



JUNE. 



First Period. 



Seasonal Notes. 



Make a consideration of the prelimiiiai'y mea.?ures that 

 are required for preparing bu.sh land that is eventually to 

 form a limo, orange, cacao, or rubber plantation. Discuss the 

 best methods of clearing such land from bush or forest. 

 How would you arrange for the land to be lined, holed and 

 planted? At what time of the year is it best for this to be 

 done, and why? When land is being opened up in this way, 

 it is necessary to realize the importance of the provision of 

 a good system of drainage. 

 Give an account of any simple 

 way of surveying land with the 

 intention of obtaining sach in- 

 formation as will enable the 

 drains to be dug where they 

 will best fulfil their purpose, a. 

 Would you be likely to obtain g 

 suggestions as to the varying .3 

 need for drainage, over the area ^ 

 dealt with, from the kind and 

 state of the plants found grow- 

 ing there? If so, what will prob- 

 ably be the nature of these indi- 

 cations? It is important that 

 the work of road-making needed 

 in the first season should be 

 completed before the crop is 

 harvested, in order that the 

 latter may be i-emoved easily and 

 quickly from the plantation. 



20 



Fk; 



In relation to sugar production, it will not be out of 

 place at the present time to give a few suggestions in connex- 

 ion with the principles of .sugar-boiling and the way in which 

 the method of boiling that is employed effects the product ob- 

 tained and the proportion of.sugarrecovered. In order to simplify 

 the matter, Figs, .5, 6 and 7, taken from Watts 's Introductory 



formed, and therefore of crystallizable sugar lost, is greatest 

 in the first-mentioned method and decreases in the order 

 given. As the formation of glucose is related to the tempera- 

 ture to which the juice has been subjected, it is ea.sily under- 

 stood that the extent of this may be reduced by making the 

 juice boil at as low a temperature as possible. This leads to 

 the consideration of the use of the triple effect and the 

 vacuum pan, in which the juice is boiled under continually 

 decreasing pressures so that its temperature is kept from 

 rising, as far as is possible, lleference to Figs. 6 and 7 will 

 easily explain the principle of the triple effect and the vacuum 

 pan. 



In the former, the diagram shows how the juice in the 

 second and third vessels is heated by the steam from the 

 evaporating juice in the preceding one — a matter that is 

 rendered feasible by reducing the pressure in the succes- 

 sive parts of the apparatus. As the liquid boils when the 

 pre.ssure of its vapour reaches that of the pressure on 

 its surface, the temperature of 

 the juice is always kept below 

 about 120° F. by decreasing the 

 air pressure until this is least 

 in the vacuum pan. Fig. 7 

 presents an explanation of the 

 working of the last-mentioned 

 piece of apparatus, where the 

 pressure is decreased by means 

 of the pump D, and the vapour 

 which arises in the pan A is 

 condensed in the pipe C and 

 the condenser E. By keeping 

 these simple diagrams in mind 

 when examining the actual appa- 

 ratus, an understanding of the 

 working of the latter will be more 

 100 readily olHained. 



Questions for Candidates. 



PEELIMINAKY QUESTIONS. 



(1) State the precautions to be 

 taken in mixing manures. 



("2) What is the use of chlorophyll to plants? 

 (3) Explain what is meant by ' plant food '. 



80 



40 60 



Sucrose 

 5. FoRM.\TiON OF Gluco.se IX Makixl; Sugar 



Tr 



y V 



:3 



r'r 



J \ 



^ 



STEAM FROM 

 JUICCINVtSSELI 



J V 



I ,5TtAM FROM 

 JUICE IN VCSSEL2 



FiG. 6. Diagram of Triple Effect. 



Manual for Sugar-Growers, are reproduced here. In the first 

 of these, the curves show the relation between the percent- 

 ages of glucose and .sucrose in the syrup, in the case of 

 muscovado manufacture, the steam pan or St. Croix method, 

 the making of concrete sugar, and in the vacuum pan method. 

 The slope of the curve shows that the proportion of glucose 



Fig. 7. Diagram of Vacuum Pan. 



intermediate questions. 



(1) Give a classification of manures. 



(2) W'hat are the advantages of the rotation of crops? 



(3) Describe methods for preparing starches. 



FINAL QUESTIONS. 



(1) Give an account of what is meant by 'dry farming'. 



(2) Discuss the conditions of an agricultural industry 

 well known to you, in relation to the existence of the vege- 

 tative propagation of plants. 



(3) Indicate the actual effects of continuous seed selec- 

 tion, in the case of a crop with which you are familiar. 



