six o'clock
`` Never open the shutter of your camera until you are certain you are ready to take the picture , and never attempt to develop a plate or a film until you are sure your chemicals are properly mixed , and until you are sure you have everything at hand with which to work , and until you are sure the plate or film is properly protected from the light . '' The boys were surprised when Mr. Jally announced that it was supper time and that he must go home . `` Gracious ! And I told my aunt we 'd be to supper by six o'clock ! '' exclaimed Shep . `` We 'll have to leg it to her house . '' `` Come again to-morrow at nine o'clock , '' said the photographer , and this the chums promised to do .