DEAR SIR,--I have received your letter, and, in answer to it, must observe that such is my opinion of both your industry and abilities that it would give me pleasure to serve you, and I should with the greatest willingness recommend you to any situation for which I knew you qualified. That you could in time qualify yourself for the situation of operator there is not the smallest doubt, but still it must have been evident to you that if _you_ had acted in that capacity last year, imperfect as the lectures were, they must have been much more so; for though I had an operator capable of preparing any experiments that could be made, still it was with the greatest difficulty that I could get through it. How, then, could I have done had my time been taken up with instructing an operator? And, having the greatest number of chemical things to prepare, I could not have got through it with any credit to myself or satisfaction to the managers. You are better acquainted with the duty of an operator than you were before the commencement of the lectures, and can therefore form some judgment concerning the knowledge requisite and the labour which it requires. It is unnecessary to say that an operator must give up his whole time to it; and, as we are to have a good laboratory, it seems to me necessary that he should be a good practical chemist, which he cannot be without working some years in a laboratory. Sadler could do anything in that way, and, were he a little more steady, would be invaluable in the Institution. You say nothing what has become of him. I was in hopes he might have been employed again next year. Indeed, the managers ought, in my opinion, to endeavour to have an operating chemist who would be permanent. That you could in time do everything required I am very far from doubting, and, should it be the wish of the managers, I shall be far from opposing it; on the contrary, were you qualified, there is not one person whom I should so much wish to have it. But, before you come to a determination, you must well consider whether you would relish the many dirty jobs to which it will subject you as well as the labour; and, if it be still your wish and determination, it would certainly be proper to attend an autumnal course of lectures. If it be your intention to remain in the Institution and to continue as operator, which probably might be carried on along with the School of Mechanics (though of this I am not certain, as an operator’s time ought to be dedicated to natural philosophy), I would do all in my power to instruct you properly; but to have the weight upon myself without the prospect of being relieved from it another year is what I dare scarce look at.