going a great deal easier if there is a windbreak along the north and west sides of an orchard."

"Grand Valley farmers use more smudge pots than those in Utah and light them more often. When a frost is expected, the town people give free assistance to the farmers in keeping their smudge pots going. It requires considerable experience to keep them fired up, especially the coal burners. The oil pots are easier to light and refill."

ORCHARD HEATERS

In Nevada, where the minimum temperatures are low and sudden, and of long duration, the best orchard heater should be an oil burner, possessing large capacity for fuel and the means to increase the flame quickly in response to a sudden or rapid fall of the temperature. Heaters of small capacity and lacking the means of regulation would be insufficient. They would require refilling on nights when the temperature was low and the heating was long continued, and for economical heating a large number of them must be held in reserve for use when the temperature is at its lowest. This would require additional aid in refilling the heaters first lighted and in lighting the others.

Owing to the cheapness of oil over coal in Nevada and its handiness for use, all heaters using other fuel have been ignored.

However, in places remote from the railroad or where wool fuel can be obtained at a moderate price, the use of wood fires may be advisable or even imperative. The value of sagebrush for heating is problematical.

Of the heaters with which the writers are familiar, only the Hamilton Reservoir Orchard Heater seems to meet the requirements, though the others may be more efficient than their appearance seems to warrant. A few heaters were subjected to test by the Walts Brothers with the result that the Hamilton Heater was adopted exclusively.1

The Hamilton Heater and two others of different design are shown in Plate VI. The characteristic feature of the former is its large size (it holds three gallons) and its sliding cover, by means of which the actual area of burning oil can be accurately regulated. An apron, which hangs from the cover, assists in preventing the oil beneath the latter from igniting to any considerable extent. For ordinary use the cover is slid back to about the third draft hole. But if greater heat is required, the cover can be drawn farther back and the area of burning oil thereby proportionately increased. When the heater is not in use, the cover is closed tight to prevent evaporation of the oil and to exclude moisture.

1. The writers regret having had no personal experience with other styles of heaters than the Hamilton, for the smaller initial price per heater with the possibility of increasing the effectiveness of small heaters by the relay system is attractive to many. The heat efficiency of the various orchard heaters is given in some of the bulletins quoted under Additional Information on Frost and Orchard Heating at the end of this bulletin.

Arrangement of Heaters

According to the writers' experience, two considerations should be paramount in the arranging of the orchard heaters to do the most efficient work: (a) in general, the smoke and heat should be concentrated on the windward side of the orchard, and (b) in particular, where the most valuable trees are found. Especially is this true if a heater cannot be provided for every tree. If the wind is strong and the windward rows are valuable, a double row of heaters should be placed several yards to the windward to cover these rows with an efficient smudge. The rows farther within the orchard, by the increasing interposition of their branches, will cut down the force of the air currents and consequently hinder the sweeping away of the smoke.

With regard to the individual trees, it is well, where possible, to place a heater directly beneath the canopy of the tree, or in such position beneath it that the heat and smoke currents sent up by the heater will pass through the foliage and break up any sluggish masses of cold air. If a heater is not available for each tree, it would be better, as stated above, to concentrate the heaters beneath the most valuable trees, employing even two or three heaters where the tree is large or exposed to the wind, and to arrange the remainder of the heaters in such a manner as to shroud the orchard in smoke. If the covering of smoke can be maintained, it will be comparatively easy to increase the heat beneath it several degrees above the temperature of the open air outside.

In case the orchard is situated in town where the ground is covered with lawn, the grass can be fully protected by elevating the heaters upon bricks, two bricks being laid flat-wise one upon the other beneath each end of a heater.

FUEL OILS

Other things being equal, the most efficient fuel oil for orchard heating is that which makes the heaviest smoke, for, just as the presence of haze or clouds hinders rapid radiation of heat from the ground, so the canopy of smoke over the top of the orchard reduces the radiation and retards the rapid fall of the temperature. In addition to this the smoke serves as a roof to hold in the heat sent up from the flames of the burning oil. Indeed, without this roof of smoke the clear flames, such as are associated with oils of a higher grade, would be inadequate to raise the temperature of the orchard much above that of the outside air. Especially is this true when the temperature is low and the radiation of the heat from the flames is unhindered.

As previously stated, the grade of fuel oil used by the Walts Brothers was No. 23. Both No. 28 and No. 22 were used at Church's

Orchard, the latter being found far superior to the former in smoke and consequently in heat efficiency. The difference in asphaltum content between No. 23, a special mixture, and No. 22, a standard oil, is slight; the price is practically the same. The objection made by Dr. Kennedy (Station Report No. 732, p. 23) to the cruder grades of oil on account of the water in them, should be made rather against the water residue that settles to the bottom of the receptacle, and not to the water in solution. This water residue is found in all oils and should be carefully drained off before the oil is poured into the heaters. If this precaution is taken, the explosion of the oil due to the generating of steam from the surplus water can be wholly avoided. Such explosions were almost entirely absent in the experiments of the Walts Brothers with the low grade oil they used, while at Church's Orchard frequent inconvenience was suffered from explosions in the No. 28 oil used at the beginning of the experiments. The only explosions of the low grade oil occurred when a supply admittedly drained from the bottom of the oil tank and heavily laden with water was used. Experience indicates, therefore, that the cruder oil is not only more efficient but is safer. It is also one-third cheaper.

The objection made by some to the use of fuel oil, on the ground that the deposition of soot upon the blossoms hinders their perfect development, does not seem to be well founded. The trees most thickly covered with soot were as heavily laden with fruit as were those far cleaner. However, it is possible that pollenation had already taken place before smudging was begun. Furthermore, despite the fact that the trees were unpleasant to touch for some time after smudging operations were ended, the matured fruit seemed to bear no traces of discoloration.

Method of Igniting the Oil

In small orchards, where speed is not essential, a very simple. and safe method of igniting the oil is to drop a wick of burlap or other cloth into a corner of the heater and light the saturated portion by an oil torch or a candle. A piece of paper will also serve the purpose. When the heaters are not far apart a wick can be kindled at one burning heater and carried to the next.

In large orchards, where the heaters should be already in position. and filled, the speediest and most economical method is to use a gasoline trigger can and a torch, but it is advisable and safer for two people to do the work, one opening the heaters and pouring the gasoline upon the oil, the other applying the torch.

The gasoline can is shown in Plate VI, and may be obtained from the Hamilton Orchard Heating Co. A similar lighter is made. by John Steel, Omaha, Nebraska. Its general design appears in