Long began to exhibit watercolours early in his career, while he was a student of Julian Ashton.
Most of Long’s watercolours, however, were painted at the beginning of the 20th century, and can be viewed as part of a Federation period revival of interest in watercolour painting.
In many of his watercolours he delighted in depicting the reflections - in the canals; on the sea and in the puddles on the street.
He often used evocative, pastel colours – and frequently captured the scenes at the ‘mystic’ hour at the end of the day. Wherever he went, Long sought the poetic in the landscape and introduced this into his watercolours.