The State Hermitage Museum in St. Petersburg houses a relatively small but choice collection of 16th- to 19th-century British paintings, among them Thomas Gainsborough's vibrant Portrait of a Lady in Blue (c. 1770) and his rival Sir Joshua Reynolds' vast Infant Hercules Strangling the Serpents (c. 1786), commissioned by the Russian Empress Catherine II and symbolizing a young Russia's growing strength. 135 paintings--works...