AA to JA [Braintree, 12-23 November 1778]
I will not finish the sentence, my Heart denies the justice of the acqusation, nor does it believe your affection in the least diminished by distance or absence, but my Soul is wounded at a Seperation from you, and my fortitude all dissolved in frailty and weakness. When I cast my (Eye) thoughts across the Arl aantick and view the distance, the dangers and Hazards which you have already passd through, and to which you must probably be again exposed, e'er we shall meet, the Time of your absence unlimitted, all all conspire to cast a Gloom over my solitary hours, and bereave me of all domestick felicity.
It's an intensifying device that Abigail Adams uses to emphasise the cumulative effect on her state of mind of all the travails and obstacles she imagines her husband being exposed to.
Nowadays, someone employing the same device would probably insert a comma between the two instances of 'all'.