Page:Life Movements in Plants.djvu/199

 great tension on the plant, which interferes with the normal rate of its growth. The friction at the bearings also becomes added up by an increase in the number of lovers, and this interferes with the uniformity of the movement of the. last recording lever. For Securing further magnilication, additional material contact has, therefore, to be abandoned. I have recently been successful in devising an ideal method of magniﬁcation without contact. The movement of the lever of the Urescograph upsets a very delicately balanCed magnetic system. The indicator is a rotlected spot of light from a mirror carried by the deﬂected magnet. Taking a single lever with the lengths of two arms 12:") mm. and 21' mm. respectively we obtain a magniﬁcation of 50 times. The magnetic system gives a further magniﬁcation of 20,000 the total magnilicttion being . thus a million times. This was verified by moving by means of a micrometer screw the short arm of the lover through 0005 mm. The resulting dellection of the spot of light at a distance of 4 metres was found to be 5,000 mm., or a million times the movement of the short arm. It is not difﬁcult to produce a further magniﬁcation of 50 times by attaching a second lever to tho lirst. The total magniﬁca— tion would in this case be 50 million times.

A concrete idea of this will be obtained when we realise that by the Magnetic Crescograph a magnification can be obtained which is about 50,000 times greater than that produced by the highest power of a microscope. This order of magnification would lengthen a wave of sodium light to about 3,000 cm. I am not aware of any existing method by which it is possible to sec ire an amplification of this order of magnitude. The application of this will undoubtedly be of great help in many physical inVestiga- tions, some of which I hope to complete in the near future.

Such an enormous magnification cannot be employed in ordinary investigations on growth, for the moving spot