In 1853, the chemist Robert Hare conducted experiments with mediums and reported positive results. Other researchers such as Frank Podmore highlighted flaws in his experiments, such as lack of controls to prevent trickery. Agenor de Gasparin conducted early experiments into table-tipping. Over a period of five months in 1853 he declared the experiments a success being the result of an "ectenic force". Critics noted that the conditions were insufficient to prevent trickery. For example, the knees of the sitters may have been employed to move the table and no experimenter was watching above and below the table simultaneously.