I'm 17 and I bought Hamilton Writings and I'm having a very rough time reading through it normally, especially his earlier writings. I can sort of get a general gist but I really want to be able to appreciate and understand this man's thoughts to the fullest extent I can. So is there a structure difference or is my vocabulary just bad and I need to "git gud?"
I find myself having to read a letter 5 or 6 times to understand it, but basically, I'm just asking for advice or know-how.
Example of Something I don't get at all: "Herewith you have duplicate of my two last letters of the 27 November & 10th Ulto....Your Sloop Thunderbolt arrivd here the 29th of the preceding Month with 41 More Skeletons/ A worse parcel of Mules never was seen; she took in at first 48 & lost 7 on the passage."
I assume it has something to due with trade accounts, but what on earth is a Sloop Thunderbolt? Who is "she?" What's an "Ulto?"
Etc.
"Ulto." is short for "ultimo" meaning "last" (i.e. the last month before the current month; similarly, you might also encounter "inst." or "instant", meaning the current month).
A sloop is a type of ship; Thunderbolt must be the name of this particular ship. "She" refers to the ship (until the mid-20th century or so, ships were often referred to as if they were female). So they loaded 48 mules on the ship, 7 died on the way and 41 arrived alive but starving and emaciated (hence "skeletons").
It might be a good idea to find a good academic edition with explicatory annotations, if you can. I'm not hugely familiar with Hamilton's writings, but I'm sure someone can recommend a good one.
Learning to read documents from the past is a skill like any other, and it's one you can work at, but there's absolutely no shame in reading someone else's 'translation'. A good dictionary is helpful, when reading more archaic forms of english, but at the age of 17 I wouldn't sweat not being able to pick up and casually read an enlightenment intellectual's correspondence. If you want to get an insight into Hamilton's political thought, it might be a better idea to read things he wrote for publication first, such as the Federalist Papers, since those are written to explain and persuade, rather than private letters which are full of abbreviations and have less of a need to explain what they're talking about.
As for the specific example you gave:
"Herewith you have duplicate of my two last letters of the 27 November & 10th Ulto
Enclosed/with this thing here, you have copies of my last two letters - one written on the 27th of November, one on the 10th of the last month ('Ulto' is a contraction of the Latin Ultima, 'the last').
Your Sloop Thunderbolt arrivd here the 29th of the preceding Month with 41 More Skeletons/ A worse parcel of Mules never was seen
A sloop is a kind of sailing ship, light and fast, commonly used to haul cargo in the eighteenth and early nineteenth centuries. Thunderbolt is the name of the ship. It arrived at wherever Hamilton is writing from on the 29th of the preceding month. He's describing the donkeys (I presume, unless some facet of 18th-century American dialect is eluding me) as 'skeletons'; from this, we can infer that they're worn-down and emaciated from their sea journey. 'A Worse parcel of Mules never was seen' is hyperbole - 'you never saw a sorrier sight'.
she took in at first 48 & lost 7 on the passage.
'She' here refers to Thunderbolt, again: ships are always referred to as 'she'. Thunderbolt loaded 48 'mules' wherever it started, and 7 died in transit.
So yes, it's a letter to someone describing the state of the cargo of a trading ship when it arrived at Hamilton's location.