I just double checked this online 1948 GE catalog, turns out the lamp life by 1949 was increased to 4000 hours at 5 hours per start, but still thats very short compared to even todays problematic MH lamps.
Even fluorescent lamps had quite short life back then! By the time of their introduction the longest lasting tube could burn for 2 500 hrs if I remember, I think it was the F100T17. Some T5s were only rated 1 000 hrs!
Those early mercury lamps have a glass arc tube. Operating them horizontally would cause the upper half of the arctube to overheat and fail. Newer quartz arc tubes doesn't overheat and can be operated in all positions. I think it has something to do with the better arc restriction performances of quartz.
Form 109s had an arc centering electromagnet that magnetically brought the arc back to the center of the arc tube, which also solves the overheat problem.
Also the quartz arc tubes operate at a higher pressure which constricts the arc, allowing less upward bowing during horizontal operation.
The reason this A-H1 lamp is burned base up is because thethe arc tube exhaust tip must face up, for maximum efficiency by allowing all of the mercury to vaporize. If the tip faced down, some of the mercury will stay there and the lamp won't be as bright.
These medium pressure mercury lamps, must be operated in a vertical position. Horizontal position, would cause the arc to bow upwards and overheat the upper region of the glass arctube.
"Form 109s had an arc centering electromagnet that magnetically brought the arc back to the center"
You can logically deduce that the arc was not in the center. And I am sure everyone knows that an arc doesn't usually bow downwards XD. You don't need to explain everything again, just add that particular information, like this:
"To be more exact, in the A-H1 lamp the arc bows upwards when operated horizontally. That's why it must be operated vertically."
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Form 109s had an arc centering electromagnet that magnetically brought the arc back to the center of the arc tube, which also solves the overheat problem.
The reason this A-H1 lamp is burned base up is because thethe arc tube exhaust tip must face up, for maximum efficiency by allowing all of the mercury to vaporize. If the tip faced down, some of the mercury will stay there and the lamp won't be as bright.
"Form 109s had an arc centering electromagnet that magnetically brought the arc back to the center"
You can logically deduce that the arc was not in the center. And I am sure everyone knows that an arc doesn't usually bow downwards XD. You don't need to explain everything again, just add that particular information, like this:
"To be more exact, in the A-H1 lamp the arc bows upwards when operated horizontally. That's why it must be operated vertically."