The painting was one of a number of British works challenging the set categories of the rigid, French-dictated hierarchy of genres in the late 18th century, as other types of painting aspired to be treated as seriously as the costumed history painting of a Classical or mythological subject. In some respects the "Orrery" and "Air Pump" subjects resembled conversation pieces, then largely a form of middle-class portraiture, though soon to be given new status when Johann Zoffany began to paint the royal family in about 1766. Given their solemn atmosphere however, and as it seems none of the figures are intended to be understood as portraits (even if models may be identified), the paintings can not be regarded as conversation pieces. The 20th-century art historian Ellis Waterhouse compares these two works to the ""genre serieux"" of contemporary French drama, as defined by Denis Diderot and Pierre Beaumarchais, a view endorsed by Egerton.