On the Verge by Eric Overmyer

Three Victorian lady explorers set out on an adventure that takes them to darkest Africa, highest Himalaya and Terra Incognita. The mirthful safari spins into time travel as the three sister sojourners, equipped with dialog as pithy as their helmets, thwack their machetes through the wilderness. These intrepid trekkers put the lie to any charge that they are representatives of a weaker sex.