slang or flang in 1749?

[Joel S. Berson]

Can someone tell me what the "slang" or "flang" in the following is?

On the Report of a British Fleet being to be sent to the Baltick.
When War subsided in the South,
Bellona seem'd to close her Mouth,
Her Cheeks were smooth, her Arms were slang,
and down her Trumpet careless hung;
She look'd so tranquil on the Nations,
They all appear'd like near Relations.

["slang" appears to begin with the ligature "sl" (no crossing bar on
the long s), but it might instead be a typesetter's error for "fl".]

Boston News-Letter, 1749 June 8, page 1, col. 2.  Headline: "From the
London Magazine for the Month of March 1749".  EAN.

Joel

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