Complex sentence: According to the Dictionary of National Biography, they became acquainted with Sir James Gray, K.B., the British resident at Venice, prior to visiting Greece, and through his agency, they were elected members of the Society of Dilettanti in London.
Split into simpler sentences: According to the Dictionary of National Biography, they became acquainted with Sir James Gray, K.B., the British resident at Venice, prior to visiting Greece. Through his agency, they were elected members of the Society of Dilettanti in London.