A camshaft rotational phase detecting apparatus for an engine provided with a variable valve timing control mechanism which controls a camshaft rotational phase of an engine valve to a target camshaft rotational phase by varying a rotational phase of a camshaft relative to a crankshaft. The cover is pivoted to the body, such that the cover is open relative to the body, and therefore elements in the body are exposed. In certain embodiments, the frozen particles provide vehicles for delivery of particular agents.