In 1799, the first volume of the West-Country Collections was issued. Half consisted of Davys essays On Heat, Light, and the Combinations of Light, On Phos-oxygen and its Combinations, and on the Theory of Respiration'. On 22 February 1799 Davy, wrote to Davies Giddy, "I am now as much convinced of the non-existence of caloric as I am of the existence of light."