The Duchess of Curiosities, Harley Gallery, Worksop

At a time when the doctrine of Instantaneous Creation was being questioned, the ambition of Margaret Cavendish, the Duchess of Portland, was to describe and publish details of every unknown species in the world.

By definition, her project was incomplete when she died in 1785, but it had enabled her to contribute to and facilitate debates about nature and natural laws through observation, classification, measurement and experiment, a century before the publication of Charles Darwin's The Origins of Species (1859).

Her collection was housed at her country home, Bulstrode Park in Buckinghamshire. Known as the Portland Museum, it was conceived as a philosophical project of wonder and delight. As such, it possessed the very qualities that many museum collections struggle to meet today.

The Portland Museum was one of the largest and most significant natural history collections ever assembled, and was supported by a team of botanists, illustrators and naturalists.

Sea captains, naturalists and professors were employed to procure acquisitions from around the globe; and the Duchess contributed to the costs of several expeditions, including Captain Cook's 1768 voyage around the world, as a way of acquiring objects.

The provenance of shells in the Portland Museum alone not only indicates the extent of British exploration in the 18th century, but the scope of her conchological ambition. They were collected in Tahiti, the West Indies, New Zealand, Hawaii, Sierra Leone, Madagascar and Norway. Birds' nests were acquired from remote regions in China and Japan.

The Portland Museum drew visitors from across Europe - among the most famous was the French writer and political theorist Jean-Jacques Rousseau. The Duchess's friends numbered fellow collectors, including Horace Walpole. They not only came to Bulstrode to visit the museum, but to enjoy the shell grottoes, the botanic garden, aviaries, and menagerie in the park.

The sheer scale of the collection is revealed in the catalogue of the auction that took place in 1786, in which 4,000 lots were sold over 35 days. While it doubtless counted as one of the great celebrity auctions of its time, the sales catalogue is regarded as the first published type description of many species and, as such, is indicative of the vast work of classification undertaken by the Duchess, her curator and botanist.

But 200 years later, the Duchess and her life's work have been forgotten. Her name lives on in a rose named after her, and the Portland Vase, one of her late acquisitions that subsequently became one of the treasures of the British Museum.

The Portland Museum's collection only survives as fragments - in natural history specimens scattered among museum collections all over the world. The house at Bulstrode was demolished in the 19th century.

The exhibition, the Duchess of Curiosities, housed in the Treasury of the Harley Gallery celebrates the Duchess of Portland's life and work. By comparison with significant male collectors, such as John Tradescant or the Duchess's contemporary, Hans Sloane, whose lives are documented and whose collections are remembered as the bases of the Ashmolean and British Museum, the Duchess of Portland and her collection are forgotten.

According to Rebecca Scott, whose biography of the Duchess accompanies the exhibition, many of Margaret's interests could be perceived within the context of what was fashionable among wealthy women of her time.

Collecting was regarded 'as an antidote for frivolity and an alternative to the card table', and the study of science as part of 'general and polite culture'. By the 1780s, botany was particularly fashionable.

But few other women had the Duchess's buying powers or her intellectual prowess. The scale of her collecting was made possible by an income derived from some of the richest aristocratic families in England.

Far from being a rank amateur, she was described as 'a Great Naturalist' and she employed internationally renowned botanists to join the intellectuals gathered at Bulstrode.

According to Scott, the Duchess's collection not only constituted an ordered and classified museum, intended to demonstrate scientific truths, but Bulstrode was a kind of university - a salon that brought together a group of people who could discuss the objects in the collection in terms that embraced the most sophisticated and controversial natural philosophies of their day.

But the fortunes of her collection, and indeed that of her immediate family, were ultimately subject to male vagaries. Despite coming from a family of collectors, she witnessed first-hand the decline and dispersal of their collections.

Her grandfather, Robert Harley, was one of the greatest book and manuscript collectors of his day; her father, Edward Harley, extended his father's collection, but was forced to sell Wimpole Hall, where the collection was housed, and died dispossessed. His collections were sold and the manuscripts acquired for the state, which helped to found the British Library.

Margaret's decision to auction her own collection after her death was prompted by her elder son's outstanding election expenses (William Bentinck, who was prime minister under George III) and the debts of her younger son, plus the fact that none of her children inherited her passion for collecting.

All this is reflected in the Harley Gallery's intimate, but stunning exhibition. It combines the scientific with the domestic; the collected with the commissioned.

Natural history and geological samples are displayed alongside a recipe book for cures, and classification systems alongside descriptions of the chaotic nature of the social life of the house (in a stereotype of the working women, which matches the portrayal of the pioneering photographer Julia Margaret Cameron a century later).

Hopefully, this exhibition will inspire other curators to consider the place of women in the history of museums.

Sara Selwood is the head of the department of cultural policy and management at City University, home of the forthcoming Cultural Leadership programme for women

Project data

Cost: £32,000

Funder: Harley Foundation

Curators: Lisa Gee, Derek Adlam

Exhibition designer: Real Studios

Exhibition ends: 1 March 2008