Back at home, a quick search provided the answer: 'life'. Unsurprisingly, the inscription was a popular one for Victorian water fountains - London Remembers records the same motto at St Dunstan's in the West, Fleet Street.
This example seems to have been provided by an anonymous philanthropist concerned at the poor quality of water available locally. (Local wells were polluted by sewage.) The District Board of Works recorded in 1860 that 'A lady residing in the neighbourhood of London is anxious to be permitted to put up a Drinking Fountain at her own expense in this Parish and prefers to place it in Lincoln's Inn Fields'. The following year, this fine and rather elaborate fountain was put in place.