HARPENDEN, an urban district of Hertfordshire, England, 25 m. N.W. by N. from London by rail. Pop. It is an outlying residential district of London. The church of St. Nicholas is modern except the Perpendicular tower. In the Lawes testimonial laboratory there is a vast collection of samples of experimentally grown produce, annual products, ashes and soils. Sir John Bennet Lawes (d. 1900) provided an endowment of £ioo,000 for the perpetuation of the agricultural experiments which he inaugurated here at his seat of Rothamsted park, and the Rothamsted Experimental Station (q.v.) plays a foremost part in modern agricultural and botanical research. There are some rubber and hat manufactures.