First of all, apologies if this is the incorrect section to post this.
At the moment I'm curating at the local gallery where there is an exhibition of local vintage photographs from three generations of a family of photographers.
One of the shots we're exhibiting is from around 1880 and of a street view looking down a long road where there is plenty of life going on, several horse-drawn carts, people walking, kids running etc.
My question is about the exposure as it's been puzzling several people, myself included.
How can the photographer have managed to capture a moment in needle-sharp focus with all that movement going on and using the equipment that he would have had to hand?
This is the camera that he actually used to take the shot...(by the way this is what he referred to as his 'portable' camera) -

If you want to see the image in question, go and click the image titled 'Drying sails at Wick'

Thank you in advance for any help.