Train

"Indeed! My mistress told me that you were likely to call. She left this morning with her husband by the 5:15 train from Charing Cross for the Continent."

(Aventure I, A SCANDAL IN BOHEMIA pg. 17)

Mechanised rail transport systems first appeared in England in the 1820s. These systems, which made use of the steam locomotive, were critical to the Industrial revolution and to the development of export economies across the world. They have remained the primary form of land transport ever since for most of the world.

Link --> History of rail transport - Wikipedia

Image source --> brownhillsbob.com

Photograph

"You see," remarked Holmes, as we paced to and fro in front of the house, "this marriage rather simplifies matters. The photograph becomes a double-edged weapon now. The chances are that she would be as averse to its being seen by Mr. Godfrey Norton, as our client is to its coming to the eyes of his princess. Now the question is, Where are we to find the photograph?"
(Aventure I, A SCANDAL IN BOHEMIA pg. 13)

The first permanent photograph was developed by Thomas Wedgwood in 1790, however, it wasn't until 1822 that an actually clear photograph was made by a French inventor, Joseph Nicéphore Niépce. Thanks to the evolution of chemstry, the process of photo development evolved throughout the 19th century. In the Victorian Era, many chemical process were invented in order to reveal those photographs, examples of which are the collodium process, gelatin process and lifochrome process.

Scissors-grinder

"There was a group of shabbily dressed men smoking and laughing in a corner, a scissors-grinder with his wheel, [...]"

(Aventure I, A SCANDAL IN BOHEMIA pg. 13)

In the Victorian London it was common to see scissors and knife grinders riding their carts along the streets. The grinding mechanism was fairly simple, it consisted of a pedal moved grinding wheel mounted on a cart. In later models the grinder wheel would be mounted on bicycles in stead of a cart.

Links:
Image Source
Historical references

Lamps

"It was a quarter past six when we left Baker Street, and it still wanted ten minutes to the hour when we found ourselves in Serpentine Avenue. It was already dusk, and the lamps were just being lighted as we paced up and down in front of Briony Lodge, waiting for the coming of its occupant."

(Aventure I, A SCANDAL IN BOHEMIA pg. 13)

The first public street lighting with gas was demonstrated in Pall Mall, London on January 28, 1807 by Frederick Albert Winsor, and it's mechanicsm was used for building all sorts of lamps throughout the entire Victorian Era. The street gas lights worked the same way as the house gas lights where the flame from the lighted gas heated up a mantle which became incandescent and gave out light.

Hansom cab

"I was still balancing the matter in my mind when a hansom cab drove up to Briony Lodge, and a gentleman sprang out. He was a remarkably handsome man, dark, aquiline, and moustached-- evidently the man of whom I had heard. He appeared to be in a great hurry, shouted to the cabman to wait, and brushed past the maid who opened the door with the air of a man who was thoroughly at home.

(Aventure I, A SCANDAL IN BOHEMIA pg. 11)

Different from a landau, a hansom cab is a kind of horse-drawn carriage designed and patented in 1834 by Hansom.The hansom cab was a popular choice because it was cheap, fast, very light and agile.

Plumber's smoke rocket

"It is nothing very formidable," he said, taking a long cigar- shaped roll from his pocket. "It is an ordinary plumber's smoke- rocket, fitted with a cap at either end to make it self-lighting. Your task is confined to that. When you raise your cry of fire, it will be taken up by quite a number of people. You may then walk to the end of the street, and I will rejoin you in ten minutes. I hope that I have made myself clear?"

(Aventure I, A SCANDAL IN BOHEMIA pg. 13)

Before the era of pressure testing, in the Victorian Era, plumbers used a smoke rocket to detect leaks in pipes. The smoking device was inserted into a pipe and lit up. Smoke would come out from whichever leaks there were in the pipe.

Landau

"Away they went, and I was just wondering whether I should not do well to follow them when up the lane came a neat little landau, the coachman with his coat only half-buttoned, and his tie under his ear, while all the tags of his harness were sticking out of the buckles. It hadn't pulled up before she shot out of the hall door and into it.

(Aventure I, A SCANDAL IN BOHEMIA pg. 11)

A landau is a four-wheeled convertible carriage suspended on elliptical springs invented in the 18th century. It was largely used in London in the 18th and 19th centuries, when it reached its full development. Until today the landal is a popular choice for the british royal family on ceremonial occasions.