On the bicentennial of Gabriel Gruber's death his speleological and karstological research in Carniola are described. Gruber carefully studied his predecessors' researches of Carniolan karst and Cerknica Lake in particular. He provided several new ideas in the joint work of Tobias Gruber and his older half brother Gabriel. For the first time in historiography Gruber's karstological references were discussed. The special concern was put on the Gruber's model of the stalactite formation where he proved his extraordinary abilities in Newton's modern mathematics. Very sad stories about Gruber-Hacquet quarrels were connected with their different opinions about karst.