Laura Lee Hope 
The Bobbsey Twins in the Country [PDF ebook] 

Join us for an enjoyable blast from the past, when kids knew how to have fun, in the second classic adventure of The Bobbsey Twins, as they head to the country to visit their Aunt Sarah for the summer. Two sets of fraternal twins, Bert and Nan, who are twelve, and Flossie and Freddie, who are six stumble headlong into excitement and family friendly mystery.
The Bobbsey Twins take a trip to visit their aunt, uncle, and cousins at their farm in Meadowbrook where they get to attend the local auction and explore the countryside. When their cousins’ prized bull goes missing, the twins search for clues to find the bull and catch the thieves!