Observation requires a respect for details

My method is based on the observation of trifles [BOSC], Watson once pointed out that I had an extraordinary genius for minutiae [SIGN] and I once stated that genius is an infinite capacity for taking pains [STUD]. It's a very bad definition but it does apply to detective work . Clues, which contributed to the solution of some of my cases, include:

A letter in which the name was in blacker ink than the address [TWIS]. This indicated that whoever wrote it was unfamiliar with the address, and was therefore not the husband of the receiver. While looking for the address, the name had dried itself, whereas the address had been blotted.

Roy, a wolfhound belonging to Professor Presbury, tried to bite him [CREE]. The professor, after taking monkey glands in an attempt to acquire eternal youth, had regressed to our ancestors and had been teasing the dog.

Parsley on top of the butter which had sunk a certain distance on a hot day [SIXN], a mark on the parapet of a bridge [THOR], and many other apparently insignificant observations were clues contributing to the solution of other cases. Those are all trifles but significant trifles. Nothing, however small, can be dismissed as insignificant.

My exploration of apparent trifles include ashes, ears, tyres, and perfumes as indicated, respectively, by the following quotations:

--- written a little monograph on the ashes of 140 different varieties of pipe, cigar, and cigarette tobacco [BOSC],
I have made a special study of cigar ashes - indeed I have written a little monograph on the subject [STUD]. This monograph is called Upon the Distinctions Between the Ashes of Various Tobaccos [SIGN].
Each ear is as a rule quite distinctive, and differs from all other ones. In last year's Anthropological Journal you will find two short monographs from my pen upon the subject [CARD].
I am familiar with forty-two different impressions left by tyres. This, as you see, is a Dunlop with a patch upon the outer cover. Heidegger's tyres were Palmer's, leaving longitudinal stripes [PRIO].
There are seventy-five perfumes, which it is very necessary that a criminal expert should be able to distinguish from each other, and cases have more than once within my experience depended upon their prompt recognition [HOUN].