PREFACE xi errors. 1 He remarks, too, that " in the measurements the height of the picture is given first, but this must not be depended upon as an unerring rule." To all these difficulties caused by former workers in the field are to be added those due to the compiler's own imperfections. How often may he have been hasty or careless or inaccurate in examining pictures or taking notes ! How often may he have regarded a genuine picture as false, or taken a forgery to be genuine ! He trusts that in his travels, extending over more than sixteen years, he has learned much ; but in many cases he must trust to his memory for the descriptions of pictures that he has not seen for ten years or more. For these faults and inadvertent errors he craves indulgence. Any additional information will be gladly received by the com- piler, and incorporated in a supplement to be published hereafter. The collaboration of my former assistant, Dr. W. R. Valen- tiner, whose name appears on the title-page, has extended to the work of Jan Steen, G. Metsu, G. Dou, P. de Hooch, J. Vermeer, M. Hobbema, and A. van de Velde. C. HOFSTEDE DE GROOT. THE HAGUE. 1 Smith says in his "Observations," vol. i. p. xxix. : "When describing a picture the writer has considered the right and left of it to be the reverse to the hands of the spectators 5 but this rule will be found so frequently falsified, arising from the incorrectness of the writers of catalogues and the various descriptions taken from old prints, that it must not be depended upon as a certain guide."
