Original sentence: (Maxwell's 1865 formulation was in terms of 20 equations in 20 variables, although he later attempted a quaternion formulation that proved awkward.) The change to the vector notation produced a symmetric mathematical representation that reinforced the perception of physical symmetries between the various fields.In the late 19th century, Maxwell's equations were only thought to express electromagnetism in the rest frame of the Luminiferous aether (the postulated medium for light, whose interpretation was considerably debated)
Edited sentence: (Maxwell's 1865 formulation was in terms of 20 equations in 20 variables, he later attempted a quaternion formulation).In the late 19th century, Maxwell's equations were only thought to express electromagnetism in the rest frame of the Luminiferous aether (the postulated medium for light).The change to the vector notation produced a symmetric mathematical representation that reinforced the perception of physical symmetries between the various fields