SECTIONAL TRANSACTIONS.—M™*. 527 
immediately and is fairly rapid; for example, a concentration of 0°33 per cent. fell 
to a third of this value in fifteen minutes. The rate of loss follows a comparatively 
smooth curve and appears to be unaffected by the presence of soil. 
A slow, steady evolution of carbon dioxide at the soil surface is almost without 
effect on the concentration in the atmosphere of the house in the daytime, and has 
but little effect on the crop. 
To determine the effect of increased concentrations of carbon dioxide on crops 
the gas was generated from sodium bicarbonate in the earlier experiments and, later, 
from portable stoves burning patent fuel. Using the bicarbonate method crop 
increases ranging from 19 per cent. to 25 per cent. were obtained when tomato plants 
were treated with 20 to 30 times the normal concentration for two and a half hours 
daily. With the stoves, increases of the order of 20 per cent. resulted when the plants 
were subjected to a concentration of six times normal for one and a half hours twice 
daily. 
Two types of plant designed to supply carbon dioxide on a large scale proved 
unsatisfactory. 
Mr. B. D. Botas.—Carbon Dioxide in relation to Glasshouse Crops. 
Mr. N. L. Hupson.—Heating of Glasshouses by Oil Fuel. 
Oil Fuel.—The oil fuel used is the resultant product after removal from the crude 
of the fractions which are volatile at ordinary temperatures. The Flash Point of the 
fuel oil commercially marketed in this country is usually about 200° F., which is well 
above the standard demanded by the Admiralty specification and by Lloyd’s. The 
high Flash Point and low Setting Point ensure safety and ease of handling under all 
climatic conditions. 
The calorific value is about 19,000 heat units a lb., the ash content about ‘01 per 
cent., and the §.G. about 0°9. 
Oil Burners.—The functions of these are to break up the oil into minute particles 
and mix with the proper proportion of air. 
Types may be classified into four groups :— 
(1) Steam Jet burners. An old type, the oil being usually fed by gravity to the 
burners, the atomisation medium being steam from the boilers themselves. 
(2) Hand controlled Mechanical Atomisation burners. Suitable for nearly all big 
steam boilers such as the water tube, marine and Lancashire types. 
(3) Semi-automatic burners. A class designed for those small boilers, for which 
hand-controlled plants are unsuitable. The installation generally consists of a storage 
tank, a pump for pumping the oil from the tank to the burner, a system of filters and 
an electric motor for driving the pump and the fan which supplies air for atomisation 
and combustion. ; 
(4) Completely Automatic burners. Particularly suitable for central heating 
and hot water supply boilers, and owing to their completely automatic action they 
are particularly suitable for heating glasshouses. The burner is usually a self- 
contained unit and is self-starting, self-igniting, self-extinguishing and self-stopping. 
Delivery.—tThis is by tanker, barge, rail, road, or in barrels. 
Advantages of Oil Fuel—{1) Absolute control of temperature by thermostat. 
This facilitates early marketing and ensures better prices, and, in addition, increases 
not only quantity but also quality of glasshouse products. (2) Economy is achieved 
by greater boiler efficiency and by reducing labour costs. It is noted that, although 
labour in Holland is cheaper than in England, the heating plant is generally inferior. 
Recent Developments.—Considerable developments are taking place in Scotland in 
oil heating for tomato growing. 
Research.—Experiments are now in progress at the Experimental and Research 
Station, Cheshunt, and at the West of Scotland Agricultural College, Auchincruive, 
and results although incomplete are so far favourable. 
Conclusion.—It is considered that ultimate success will rest with those firms who 
apply scientific methods and apply modern equipment in their works. Heating with 
oil fuel offers to the British glasshouse grower increased output, reduced costs and the 
means of successfully combating foreign competition. 
