Injection of the weft by air-jet into the free air or shed has been studied with the aid of several experimental devices. The main results obtained from this study are: 1. A nozzle with a simple tapered cylinder for its base and having a parallel tip 50mm long and 10mm in diameter gives the best performance in propelling the weft more than 100cm when the thread guide is set 20mm inside the nozzle outlet. 2. Laval tubes are unfit for weft propulsion. 3. The air speed drops sharply near the nozzle, and is exceeded, in the middle of the shed, by the running speed of the weft. 4. How to remove the point whene the air speed is exceeded by the running speed of the weft as far as possible from the nozzle with the least possible additional comsumption of horsepower for air compression is a problem which awaits further inquiry.