I see no objection to evening lectures if you can find a fit man to give them. As to popular lectures (which at the same time are to be _respectable_ and _sound_), none are more difficult to find. Lectures which _really teach_ will never be popular; lectures which are popular will never _really teach_. They know little of the matter who think science is more easily to be taught or learned than A B C; and yet who ever learned his A B C without pain and trouble? Still, lectures can (generally) inform the mind, and show forth to the attentive man what he really has to learn, and in their way are very useful, especially to the public. I think they might be useful to us now, even if they only gave an answer to those who, judging by their own earnest desire to learn, think much of them. As to agricultural chemistry, it is no doubt an excellent and a popular subject, but I rather suspect that those who know least of it think that most is known about it. [Sidenote: USE OF MODELS AND CARDS.] His fondness for illustrating obscure points in his lectures by models has been more than once alluded to. He would improvise these out of wood, paper, wire, or even out of turnips or potatoes, with much dexterity of hand. In one of his unpublished manuscripts, dating about 1826, dealing with the then recently discovered phenomena of electromagnetism, occurs the following note:-- It is best for illustration to have a model of the constant position which the needle takes across the wire: _le voila_ (Fig. 21). [Illustration: FIG. 21.] Many such simple models were used in his lectures. He leaned upon them to aid his defective memory; but they helped his audience quite as much as they aided him. Reference was made on p. 7 to his use of cards, on which to jot down notes of thoughts that occurred to him. One such runs as follows:-- Remember to do one thing at once. Also to finish a thing. Also to do a little if I could not do _much_. Pique about mathematics in chemists, and resolution to support the character of experiment--as better for the mass. Hence origin of the title _Exp. researches_. Influence of authority. Davy and difficulty of steering between _self-sufficiency_ and dependance (_sic_) on others. Aim at high things, but not presumptuously. Endeavour to succeed--expect not to succeed. _Criticise_ one’s own view in every way by experiment--if possible, leave no objection to be put by others.