twelve o’clock
`` April 19th . This morning , to my great joy , about nine o'clock , the surface of the moon being frightfully near , and my apprehensions excited to the utmost , the pump of my condenser at length gave evident tokens of an alteration in the atmosphere . By ten , I had reason to believe its density considerably increased . By eleven , very little labor was necessary at the apparatus ; and at twelve o'clock , with some hesitation , I ventured to unscrew the tourniquet , when , finding no inconvenience from having done so , I finally threw open the gum-elastic chamber , and unrigged it from around the car . As might have been expected , spasms and violent headache were the immediate consequences of an experiment so precipitate and full of danger . But these and other difficulties attending respiration , as they were by no means so great as to put me in peril of my life , I determined to endure as I best could , in consideration of my leaving them behind me momently in my approach to the denser strata near the moon . This approach , however , was still impetuous in the extreme ; and it soon became alarmingly certain that , although I had probably not been deceived in the expectation of an atmosphere dense in proportion to the mass of the satellite , still I had been wrong in supposing this density , even at the surface , at all adequate to the support of the great weight contained in the car of my balloon .