1895 THE MICROSCOPE. 13 



stumbling-blocks which amateurs are apt to encounter 

 in photo-micrography, and I find an absolutely essential 

 point to be the keeping of all the apparatus in a straight 

 line. Unless this is secured, the most elaborate appara- 

 tus and most careful focusing are but in vain, for other- 

 wise, if one edge of the field is sharp, the other goes out 

 into "fuzziness," and an even, sharp focus is a physical 

 imposibility. 



One caution. If using "apochromatics" never expect to 

 see a flat field, for the objectionable roundness noticed in 

 ocular observations will be doubled or trebled in a long- 

 focussed camera. The obvious and only remedy is: Care- 

 fully put what you want to photograph in the centre of 

 the field, and use a large-sized plate, so that you can 

 afford to stop off the edges in printing your positives. 

 In this way the curvature will not be offensive. — The 

 Photographic Times. 



An Examination for Blood. — The Bishop ot Versailles, 

 Monseigneur Goux, has submitted the famous seamless coat 

 which is preserved as a relic in the church of Argenteuil and 

 which according to tradition is stained with the blood of Christ, 

 to examination by scientific experts. For this j^urpose he 

 chose M. Philippe Lafon and M. J. Roussel, who were asked to 

 furnish an answer to the following questi )n : "What is the ex- 

 act nature of the spots on the garment known as the Holy Coat 

 of Argenieuil ?" These experts in due course certified that they 

 had made a chemical and microscopical examination of the 

 " Holy Coat." After describing in the ordinary way, the tests 

 employed, they sum up (according to the British Medical Jour- 

 nal) as follows : "From the portion of the Coat marked with 

 rust colored spots we obtained : (1) A faint green coloration, 

 with the tincture of guaiacum and the essence of turj^entine, 

 (2) the revival of the red globules of blood, with the artificial 

 serum, (3) the formation of crystals of hcemin, or of chlorohy- 

 drate of hamatin. These indications are sutficient to enable us 

 to afiirm that the spots examined are actually due to blood — 

 and to human blood. Judging by the whole of our analysis, 

 we presume that this blood is very old. 



