(_c_) If a portable fumigation chamber or gas tight vault is not available, “tarpaulin method” of fumigation may be used. Sweep clear the floor (preferably cement) where the feed is to be placed for fumigation. Stack the bags of feed in a square area to a height of 5 or 6 feet. After the feed is stacked, center four bags of feed in an upright position on top of the pile to form a gas expansion dome. Throw a tarpaulin which is large enough to cover completely the entire pile of feed over the pile. Allow a minimum margin of 2 feet on the floor for sealing. The tarpaulin should be of treated material, preferably rubberized, to prevent leakage and to be impervious to the fumigant. Seal the marginal excess of tarpaulin with filled bags or weights. The fumigant is released from the container through a tubing extending from the container under the tarpaulin to the top of the gas expansion dome. The same type of fumigant, dosage, exposure, and temperature required for vault or chamber fumigation are employed, and the same precautions are observed when removing the tarpaulin after the exposure period. If circumstances prevent a tight sealing of the tarpaulin use an increased amount of fumigant to compensate for leakage. _j._ USE AND PREPARATION OF GRIT. Grit is a prepared mixture which serves as a mechanical grinder for the food in the pigeon’s gizzard and assists in assimilation. Grit also purifies the crop and supplies lime for bone building and forming of egg shells. Many grit mixtures are available, most of which contain crushed oyster shell, gravel, sand, small sea shells, crushed limestone, salt, charcoal, and other ingredients. (1) Between 5 and 10 percent of the food fed a pigeon should be grit. Normally 5 percent is sufficient, except during the breeding season when as much as 10 percent may be fed since the parent pigeons pump grit into the youngsters when they start eating grains. (2) A preferred grit is made as follows: (_a_) Thoroughly mix (in the manner of mixing mortar) 20 pounds of medium granite grit, 20 pounds of medium oyster shell, 20 pounds of medium crushed limestone, 5 pounds of medium charcoal, and 1/8 pound of oxide of iron (hematite). Then dissolve 3 pounds of table salt in boiling water and add just enough of this solution to the mixture to dampen it thoroughly. Do not add too much water. Thoroughly mix the whole preparation and allow to dry before feeding to birds. (_b_) Each of the various ingredients in the mixture has a purpose. The granite is a grinder and pulverizes the food; the oxide of iron has a beneficial effect upon the blood and acts as a tonic; the charcoal purifies the crop, acting as a stomachic, that is, strengthening or stimulating action of the stomach. Limestone provides the materials for strengthening the bones. The oyster shells contribute lime which enters into the composition of bones and egg shells.