My dear Sir

I am very much obliged for the papers.— I feel certain that your judgment on all parts in regard to the Census is incomparably safer than mine. Firstly My impression is that it w^d be better to confine enquiry to 1^st cousins.² Secondly, I incline to think that your second form of enquiry is the best, that is if both forms are not included; in as much as second will give the proportion out of the whole population of cousins who marry & who have children.

The object of the enquiry is to ascertain whether with mankind, consanguineous marriage within the degree of cousinship is in any way injurious, & The result of such an enquiry is almost equally important whether negative or affirmative.

In England & any part of Europe the marriages of cousins are objected to by fear their supposed injurious consequences; but this belief rests on no direct evidence. It is therefore [manifestly] desirable that this belief sh^d either be proved to be false, or sh^d be confirmed so that in the latter case the marriage of cousins might be discouraged. The returns gained if the proper queries are inserted, would show whether married cousins have in their households on the night of the census as many children, as parents who are not related; & sh^d the number prove fewer, we might safely infer either lessened fertility in the parents, which is more probable lessened vitality in the offspring.

If the proportional number of cousins who marry in the whole population was once ascertained, there c^d exist a standard by which to judge whether the proportion, (already tabulated in some cases) of persons in asylums for the dumb & deaf the blind & insane who are the offspring of cousins is in excess of the proportion of cousin-offspring in the whole population.—

I fear I have written at too great length, but I have not felt sure, how fully you wished me to write.—

It is moreover much to be wished that the truth of the often repeated assertion, that consanguineous marriages lead to deafness & dumbness, blindness &c sh^d be ascertained; & all such opinion c^d be easy tested, by the returns from a single census.—

It is beyond my power of filling out all the detail, to see which of your 2 forms of enquiry w^d be best, if both are not included.– I could insert the words “married to—” with a blank, showing that the word cousin ought to be introduced; when this is the case.