"The House of Commons is a great unwieldy body, which requires great Art and some Cordials to keep it loyal"

This quote by Henry Pelham is referring to your house of Commons, the lower house of the British Parliament. Pelham is suggesting that your home of Commons is a large and unwieldy body, which it needs terrific ability and effort to keep it faithful. He is implying that it is difficult to manage such a large and varied group of people, and that it takes a lot of effort to guarantee that everyone is interacting in consistency. Pelham is also recommending that it takes a particular kind of "cordial" or friendly attitude to keep the House of Commons devoted. This might imply that it is essential to keep an excellent relationship in between members of your house of Commons, and to guarantee that everybody is collaborating for the typical good. Pelham's quote is a tip that it takes a great deal of effort to keep a big and diverse group of people working together, which it is important to preserve an excellent relationship in between members of the House of Commons.