Several writers have pointed out that riding, especially in women, may produce sexual excitement and orgasm.[205] It is well-known, also, that both in men and women the vibratory motion of a railway-train frequently produces a certain degree of sexual excitement, especially when sitting forward. Such excitement may remain latent and not become specifically sexual.[206] I am not aware that this quality of railway traveling has ever been fostered as a sexual perversion, but the sewing-machine has attracted considerable attention on account of its influence in exciting auto-erotic manifestations. The early type of sewing-machine, especially, was of very heavy character and involved much up and down movement of the legs; Langdon Down pointed out many years ago that this frequently produced great sexual erethism which led to masturbation.[207] According to one French authority, it is a well-recognized fact that to work a sewing-machine with the body in a certain position produces sexual excitement leading to the orgasm. The occurrence of the orgasm is indicated to the observer by the machine being worked for a few seconds with uncontrollable rapidity. This sound is said to be frequently heard in large French workrooms, and it is part of the duty of the superintendents of the rooms to make the girls sit properly.[208] "During a visit which I once paid to a manufactory of military clothing," Pouillet writes, "I witnessed the following scene. In the midst of the uniform sound produced by some thirty sewing-machines, I suddenly heard one of the machines working with much more velocity than the others. I looked at the person who was working it, a brunette of 18 or 20. While she was automatically occupied with the trousers she was making on the machine, her face became animated, her mouth opened slightly, her nostrils dilated, her feet moved the pedals with constantly increasing rapidity. Soon I saw a convulsive look in her eyes, her eyelids were lowered, her face turned pale and was thrown backward; hands and legs stopped and became extended; a suffocated cry, followed by a long sigh, was lost in the noise of the workroom. The girl remained motionless a few seconds, drew out her handkerchief to wipe away the pearls of sweat from her forehead, and, after casting a timid and ashamed glance at her companions, resumed her work. The forewoman, who acted as my guide, having observed the direction of my gaze, took me up to the girl, who blushed, lowered her face, and murmured some incoherent words before the forewoman had opened her mouth, to advise her to sit fully on the chair, and not on its edge.