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Darwin Correspondence Project

From J. L. Sinclair   31 December 1869

Auckland New Zealand

31 Decr. 1869.

Dear Sir,

By the last English Mail, I forwarded some memoranda to Mr. Murray, which I requested him to show you, in order that they may be noticed in “The Academy”.—1 I am extremely anxious to have your opinion on my “Theory of organic Disturbance”, and also on my Hypothetical “Law of Organic Combination”, and if you should not have leisure to write an article on them for the “Academy”, would you favour me with a letter on the subject?—2

I enclose a copy of a letter to Sir Henry Holland. which contains the leading points of my psychological researches.— This letter, & the one I sent to Mr. Murray, contain the results of my scientific labours, which you will think are most meagre, but I have had such a struggle for life that I shall never be able to do more.— Here I have been (like Kepler)3 calculating Almanacks for a livelihood, and now the season is over, I am out of employment, & have a wife & 4 children depending on my exertions!4 This would be nothing, if my wife did not happen to be a person of a nervous habit, & subject to frequent epileptic attacks, which hinders & harasses me very much. I write this hurriedly, as I do not know when I may be able again to have the postage.

If you should think my psychological investigations worth reviewing in the “Academy”, I shall be glad to see them noticed.—

By the way, I observe Mr. Murray has issued a cheap edition of my favourite Hymn writer—Heber:5 please tell him to send me a copy by post, & I shall contrive to pay him somehow.—

I am Dear Sir | very truly yours | James Leask Sinclair | Auckland. | N.Z.

To Dr. Darwin | Author of the “Origin of Species”.


Copy of a Letter from James Leask Sinclair to Sir Henry Holland   London 1869.

“Sometime in 1844, my attention was drawn to the subject of Psychology, by the study, or rather the perusal, of a little book of Forbes Winslow’s that I picked up in an Edinburgh Library.6

This thin volume was a great treat to me at the time, as it related chiefly to nervous disorders, and some passages in it on Dreams made a very serious impression on me.

Afterwards I read something on the same subject in Brougham’s “Introductory Discourse to Paley’s Natural Theology,”7 and this I made the basis of my own researches on the subject. From 1850 to 1862, I had leisure for such investigations, and I now beg to send you a brief summary of the results.—

Taking the impressions made upon the sense of sight during a day, I endeavoured to ascertain whether their reproduction in Dreams followed one or more laws, and I found, that, excluding such dreams as might be considered to arise from the state of the secretions, or from a temporary derangement of the digestive powers, they could be reduced to two, which I named “Lex Fortuitæ Impressionis”, or The Law of Oblique Impression (in Dreams), and “Lex Intensæ Impressionis”, or The Law of Intense Impression (in Dreams): in plain language, “The Law of Casual Impression,” and “The Law of Strong Impression.” In the former, the Impression enters, as it were, obliquely, or, at an angle; it is entirely unexpected, you were not seeking for it, and yet it is as liable to be reproduced as those deeper impressions which Shakespeare has so admirably depicted in his Romeo and Juliet

In 1860, & 1861, I studied the subject of Mesmerism, and arrived at another law, which I termed “Lex Habitus”, or Law of Habit. This Law is merely “That, in abnormal states of the body, the impressions made upon it, are in exact accordance with its habits in the normal state”. For instance, in the Mesmeric coma, a man speaks when his eyes are touched, not because the organ of language has been stirred, but because, from his earliest years, whenever his eyes were covered by a companion coming behind him, his first impulse has been invariably to speak. When touched on the side of the head, he may assume an offensive or defensive attitude, not because the organ of combativeness has been awakened, but because, from his earliest youth, he has been accustomed to be cuffed on the side of the head. When touched on the top of the head, again, he may appear to be elevated, not because the organ of self-esteem has been excited, but because he has been accustomed to be patted on the head in his youthful years, and the erect posture of the body that is necessary to sustain the head when touched in this way, is the ordinary attitude of people in whom sanity predominates.—”


See letter from J. L. Sinclair to John Murray, 22 December 1869.
For Sinclair’s theories, see the enclosures to the letter from J. L. Sinclair to John Murray, 22 December 1869. No letter of reply from CD has been found.
Johann Kepler.
Sinclair worked as a journalist and teacher while in New Zealand. His wife was Mary Sinclair.
The references are to Heber 1870 and Reginald Heber.
Forbes Benignus Winslow wrote several short books before 1844; Sinclair probably refers to On the preservation of the health of body and mind (Winslow 1842).
Sinclair refers to Henry Peter Brougham’s contribution to Paley’s Natural theology (Paley 1845).


Heber, Reginald. 1870. The poetical works of Reginald Heber. New edition. London: John Murray.

Paley, William. 1845. Paley’s Natural theology, with illustrative notes by Henry, Lord Brougham and Sir C. Bell; and an introductory discourse of natural theology by Lord Brougham; to which are added supplementary dissertations and a treatise on animal mechanics by Sir Charles Bell. 4 vols. London: C. Knight.

Winslow, Forbes. 1842. On the preservation of the health of body and mind. London: Renshaw.


Would like CD’s opinion on his "theory of organic disturbance" and his "law of organic combination"; hopes CD might notice them in the Academy.

Writes of his unfortunate circumstances.

Letter details

Letter no.
James Leask Sinclair
Charles Robert Darwin
Sent from
Source of text
DAR 177: 173
Physical description
3pp, encl 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 7039,” accessed on 24 September 2021,

Also published in The Correspondence of Charles Darwin, vol. 17