IT is not generally realised how far developments have gone towards perfecting a means for aeroplanes to ' land ' on ships at sea. Yet one of the most feasible suggestions that have been made, in connection with any practical scheme for a trans-Atlantic air-service, depends entirely upon a chain of ' carriers ' over the ocean upon which aeroplanes may ' land ' for overhauling and fuel. Mr. Spencer Cooper , who, until recently, was a pilot in the Navy Air Arm, will be speaking from wide experience tonight when he describes what has already been achieved to make aeroplane work at sea a practical proposition. He will tell us how the ' landing ' on such a confined space is achieved ; what exactly a ' carrier ' is like, and what some of the trials both of pilot and ships' men entail.