by John Bellairs (1989)
Johnny Dixon and Professor Childermass discover a trolley which transports them back to Constantinople in 1453 as the Turks are invading the Byzantine Empire.
Andre Norton
Time Agents Ross Murdock and Gordon Ashe, aided by a Polynesian girl and her team of telephatic dolphins, probe the mystery of the sea-planet men have named Hawaika. Its cities and civilizations have vanished, but our agents are snatched back through a Time Gate and marooned in the midst of the struggle for power that mist have destroyed the planet.
L.A. Courtenay
Alert! Alert! When the penguins splash-land on a watery planet, they find themselves in the tentacles of a monstrous sea creature. Can they escape with their ship in one piece or are they well and truly sunk?
Bel Mooney
When his family moves to a large rambling house in the English countryside, Daniel discovers an old stove which leads to a journey into the past, to 1835, where as a kitchen servant, he becomes involved in the local farm workers' dangerous plans to form a union.
Myra McEntire
"From the moment the Hourglass group violated the rules of the space time continuum to rescue a murdered loved one, time has been in flux. People from other centuries slide into our time, intruding into our space, threatening our world. Frantically seeking a way to turn back this tide, the Hourglass begins a search for the legendary Infinityglass, tracking it to the city of New Orleans, a place where the past rests easily with the present. Quiet, reliable Dune, the group's favorite geek, is selected to travel to the Crescent City and somehow retrieve the renowned object. But there's a problem. Because the Infinityglass is not an object, it's a person. A beautiful, headstrong dancer named Hallie, a girl so enticing Dune can't take his eyes off her. And time is not on her side."--Jacket.