Discovery is one of the most prevalent themes in The Time Machine and can be found in a number of contexts throughout the novel.
First of all, discovery is what enables the Time Traveller to get to the year 802,701. Through careful thought and consideration, he unlocks the secret of time travel which he unveils to his sceptical friends in the opening chapter. The theme of discovery, therefore, sets the scene for the story which follows.
Secondly, discovery is the word which best describes his experiences of the year 802,701. In this new world, he discovers two new species: the Eloi, who live above ground, and the Morlocks, who dwell below the surface. A further discovery is made in Chapter Seven, when the Time Traveller realises that the Eloi provide meat for the Morlocks, which explains their "Great Fear" and their need to sleep in close proximity.
The loss and re-discovery of the Time Machine is another key aspect of the story. The Time Traveller must overcome his fear of the Morlocks to retrieve it and return to the nineteenth century. Instead of returning home, however, the Time Traveller goes even further forward in the future, to a time when the moon has died and the sun is much hotter. It is only the discovery of a black, tentacled creature and a sense of "terrible dread" that prompts him to return home.
What becomes apparent, then, is that the concept of discovery is a driving force in the plot of The Time Machine because it enables travel, creates conflict and builds suspense.