Figure 76 comprises three drawings labelled '1860', '1940' and '1980'. Drawing '1860' is a perspective drawing of a battery with the casing shown in outline so that the insides of the battery can be seen. The casing is almost a cube and two thirds filled with what appears to be a liquid. The cube is shown to have sides about 10 centimetres in length. A relatively large vertical cylinder is in the centre and protrudes above the top of the casing. A rectangular object is positioned in the centre of the cylinder with an electrical wire connected to the top of it. The space around it is filled with a granular material. Next to the central cylinder, in the space between it and one corner of the cube, there is a much smaller diameter cylindrical rod which also protrudes above the top of the casing. There is an electrical wire connected to the top end of the rod. The large cylinder and the rod are held in position in the casing by a collar that encircles them both.

Drawing 1940 is a partially sectioned drawing of a battery and the top surface of the battery is also visible. This battery consists of an open cylindrical zinc can with a carbon rod that goes down the centre of the can but does not quite reach the bottom. The rod protrudes above the top of the can and has a screwed electrical connection that is labelled '+'. Inside the can, the rod is in a fabric bag filled with a powdered manganese dioxide and carbon mixture. The space between the fabric bag and the zinc can is filled with electrolyte paste. The top of the can has a bitumen seal. A second screwed electrical connection, labelled '-', is attached to the outside of the zinc can near its rim. The two electrical connections are at the same level above the can.

Drawing 1980 is a true section through a battery. This battery consists of an open zinc can with an external protective casing and a carbon rod that goes down the centre of the can but does not reach the bottom. The rod protrudes above the top of the can and has a flat electrical connection that is labelled '+'. The bottom of the zinc can is exposed and identified as a flat electrical connection labelled '-'. The rod is held in the centre of the protective casing by insulation material at the top and the bottom of the casing. The rod is inside a hollow cylindrical separator filled with a powdered manganese dioxide and carbon mixture. The separator has a bitumen seal at the top but there is an air space between the seal and the mixture inside the separator. Over 90% of the inside of the zinc can is taken up by the separator and the remaining space between the separator and the zinc can is filled with electrolyte paste.

 5 Engineering: pushing back the boundaries