reference to existing facts.— When language used in a document is plain in itself, but is unmeaning in reference to existing facts, evidence may be given to show that it was used in a peculiar sense. Illustrations A sells to B, by deed, “my house in Karachi”. A had no house in Karachi, but it appears that he had a house at Keamari, of which B had been in possession since the execution of the deed. These facts may be proved to show that the deed related to the house at Keamari.