Richardson's handbook of projection (1930)

1090 HANDBOOK OF PROJECTION FOR along under "Electrolyte," the resultant mixture being about 1.285 to 1.300 specific gravity. You can see then that the sulphuric acid of the electrolyte of a battery is heavier than water. On discharge, the sulphuric acid in the electrolyte mixture leaves the electrolyte mixture to combine with the positive and negative plates of the battery. As the sulphuric acid was the heavy part of the electrolyte, the mixture will, on discharge, get more like water. That is, the specific gravity of the electrolyte will be lowered. From specific gravity readings, therefore, we can tell just how much sulphuric acid has combined with the plates, and can therefore tell the extent to which the battery is discharged. Of course it follows that we can also tell when the battery is fully charged, because the specific gravity will not rise any higher, thus indicating that all of the sulphate has been driven out of the plates into the mixture. If the directions and instructions herein contained are faithfully followed by the projectionist in charge, there will be little or no battery trouble. The batteries are well and ruggedly made. There is but little about them to cause trouble. Battery trouble is almost invariably the result of carelessness or neglect in some form. You cannot mistreat or neglect storage batteries and get away with it. They will serve you well, provided you serve them well. If you do not, then they have a way of "getting back" at you, and they will do it, too. I emphasize this matter because of the fact that battery trouble is almost invariably the fault of the projectionist. True, there is always the possibility of some individual cell having structural weakness, but under the rigid inspection and tests all parts are subjected to before