Detection is a form of protection. Knowing where the radiation is a big part of the problem.
The Leyden jar was invented around 1745 and is an example the early investigations of electricity so that fits in with your time period.
The gold leaves of the jar separate when charged up, (like charges repel) and when radiation enters the air in the jar, it ionizes it, creating both positive and negative charges. The mobile negative charges neutralize some of the charge on the gold leaves and this results in the leaves coming closer together. This is the principle behind the electrostatic dosimeter. The wikipedia page shows these can be quite compact and sensitive. Quartz Fiber Dosimeter
Radiation can also discolor glass, the color depending on the impurities in the glass. So perhaps depending on how far you want to stretch the science that could serve as a warning.
Similarly there are crystals where the radiation excites an electron, and the electron is trapped, until the crystal is heated. When heated the electrons de-excite emitting a photon. These are called thermoluminescence, and the amount of light is proportional to the amount of radiation.
In terms of protection, different materials have different 10th thicknesses, or half layer values. Lead being very dense would reduce the radiation by a 10th or a half with thinner layer than a less dense material. This is true for gamma rays and neutrons. Water for example is pretty good at slowing down neutrons, and can be a form of shielding for gamma rays too, although it is not as dense as lead.
But there are also different types of radiation, alpha particles, beta particles, gamma rays and neutrons, and the type of shielding would depend on the radiation type. Alpha emitters are pretty harmless, unless ingested. Beta particles are also blocked very easily.
People are pretty smart, If in your era, people are starting to mess around with photography, then they could discover x-rays, or other forms of radiation. The first photograph was around 1826.