did you ever see one of these high pitched dog whistles well you ever hear one there was a sound the dog heard all of the sound way it was vibrating too fast for human hearing however we can take a picture of the image cast by the x ray on a specially prepared film or plate all we can see the image through a fluorescent screen one of the tablet cations is by police departments to find out what's inside th is spacious looking packages this innocent alarm clock might have been a bomb x ray inspection make sure of safety here just as a does in the field of medicine and today in the great plants where military planes and passenger liners are built safety in their construction is a sure ordered by the use of x ray giant automatic x ray cameras take photographs of all the vital parts in these machines the parts move in under the x ray tube where a one ton lead to good comes down to cover them during exposure timing and intensity of the x ray exposure are automatically controlled in the finished films the grain of the materials is examined to determine the strength of the part and to find the slightest defect these precautions are taken in order that america may build a great and powerful air fleet and equally important for the fate of the men who fly x ray has given us increased safety in the air but more of us are concerned with safety on the streets and highways the modern automobile has many safety features one of the most important being good brakes here two x ray can give us interesting inside information an x ray photograph shows that this break you has worn evenly along the full length the lining here is an x ray of a hue from another type of brake this one has worn thinner at one end and then at the other let's look at the break from which it came in this break the issues are anchored on a fixed pivot but the heat of break application expands the metal of the hubris this expansion causes varying pressures of issues against the drum resulting in an even aware of lining in the first break where the wear was uniform there is a movable linkage which allows the hue to press even me against the drum as the brake heats the movable wings compensate for expansion smoothly maintaining an even pressure at all times along the full length of the lining and so today's most modern automobile is built with brakes that give us more miles of it active service assuring the driver of greater safety and economy save smooth stops and many more of them are the result of engineering research when they designed this mechanism the engineers hit upon a simple device they copied nature the ankle acts as a pivot to distribute the pressure of all weight evenly between the toll in the heel or inside information on the ankle action let's call upon one of the newest and most startling developments of science x ray motion pictures for the first time in a theater screen we are about to see action pictures photographed with special equipment that utilizes the wonderful x rays inside information on ankle action x ray motion pictures show that  step down on the ball of the foot the ankle acts as a movable pivot allowing us to lower the heel and even up the pressure x ray motion pictures of such simple action represent an important forward step to science an engineering these remarkable pictures a lull us to see the same action in nature that has been engineered into the modern automobile brake a movable link that distributes pressure evenly and so it's the link smooth even pressure whether it's driving the modern motor car or dancing the graceful measures of a little thing ballet